The very high levels of exploitation in the western rock lobster fishery have resulted in the introduction of regional or zone-specific management arrangements in recent years. This is a permanent departure from an holistic approach to the fishery’s regulation.  A detailed knowledge of regional variations in the growth, movement and mortality of the lobsters is required to support the models assessing regional management options.

A need was identified to supplement the Fisheries Western Australia, Research Division’s resources to enable the full analysis of existing tagging data in terms of growth, movements and mortality; to undertake tagging in shallow water to assist in addressing specific management issues; to improve the level of tag recapture information from industry; and to develop a strategic approach to tagging that would assist in providing appropriate advice to management and industry, given the regional approach to the fishery’s regulation.

Tagging of western rock lobsters, using “spaghetti” tags in a dorsal or ventral (or both) position, has been undertaken opportunistically for many years but this report is concerned with data collected from 1988 to 1996.  Most recaptures of tagged lobsters were made during the first commercial season after release (approximately 75%), however, recaptures did occur for up to five seasons post-release. 

Keywords: Western rock lobster, Panulirus cygnus, tagging, migration, growth, mortality.

The very high levels of exploitation in the western rock lobster fishery have resulted in the introduction of regional or zone-specific management arrangements in recent years. This is a permanent departure from an holistic approach to the fishery’s regulation.  A detailed knowledge of regional variations in the growth, movement and mortality of the lobsters is required to support the models assessing regional management options.

A need was identified to supplement the Fisheries Western Australia, Research Division’s resources to enable the full analysis of existing tagging data in terms of growth, movements and mortality; to undertake tagging in shallow water to assist in addressing specific management issues; to improve the level of tag recapture information from industry; and to develop a strategic approach to tagging that would assist in providing appropriate advice to management and industry, given the regional approach to the fishery’s regulation.

Tagging of western rock lobsters, using “spaghetti” tags in a dorsal or ventral (or both) position, has been undertaken opportunistically for many years but this report is concerned with data collected from 1988 to 1996.  Most recaptures of tagged lobsters were made during the first commercial season after release (approximately 75%), however, recaptures did occur for up to five seasons post-release. 

Keywords: Western rock lobster, Panulirus cygnus, tagging, migration, growth, mortality.

The very high levels of exploitation in the western rock lobster fishery have resulted in the introduction of regional or zone-specific management arrangements in recent years. This is a permanent departure from an holistic approach to the fishery’s regulation.  A detailed knowledge of regional variations in the growth, movement and mortality of the lobsters is required to support the models assessing regional management options.

A need was identified to supplement the Fisheries Western Australia, Research Division’s resources to enable the full analysis of existing tagging data in terms of growth, movements and mortality; to undertake tagging in shallow water to assist in addressing specific management issues; to improve the level of tag recapture information from industry; and to develop a strategic approach to tagging that would assist in providing appropriate advice to management and industry, given the regional approach to the fishery’s regulation.

Tagging of western rock lobsters, using “spaghetti” tags in a dorsal or ventral (or both) position, has been undertaken opportunistically for many years but this report is concerned with data collected from 1988 to 1996.  Most recaptures of tagged lobsters were made during the first commercial season after release (approximately 75%), however, recaptures did occur for up to five seasons post-release. 

Keywords: Western rock lobster, Panulirus cygnus, tagging, migration, growth, mortality.

The very high levels of exploitation in the western rock lobster fishery have resulted in the introduction of regional or zone-specific management arrangements in recent years. This is a permanent departure from an holistic approach to the fishery’s regulation.  A detailed knowledge of regional variations in the growth, movement and mortality of the lobsters is required to support the models assessing regional management options.

A need was identified to supplement the Fisheries Western Australia, Research Division’s resources to enable the full analysis of existing tagging data in terms of growth, movements and mortality; to undertake tagging in shallow water to assist in addressing specific management issues; to improve the level of tag recapture information from industry; and to develop a strategic approach to tagging that would assist in providing appropriate advice to management and industry, given the regional approach to the fishery’s regulation.

Tagging of western rock lobsters, using “spaghetti” tags in a dorsal or ventral (or both) position, has been undertaken opportunistically for many years but this report is concerned with data collected from 1988 to 1996.  Most recaptures of tagged lobsters were made during the first commercial season after release (approximately 75%), however, recaptures did occur for up to five seasons post-release. 

Keywords: Western rock lobster, Panulirus cygnus, tagging, migration, growth, mortality.

The very high levels of exploitation in the western rock lobster fishery have resulted in the introduction of regional or zone-specific management arrangements in recent years. This is a permanent departure from an holistic approach to the fishery’s regulation.  A detailed knowledge of regional variations in the growth, movement and mortality of the lobsters is required to support the models assessing regional management options.

A need was identified to supplement the Fisheries Western Australia, Research Division’s resources to enable the full analysis of existing tagging data in terms of growth, movements and mortality; to undertake tagging in shallow water to assist in addressing specific management issues; to improve the level of tag recapture information from industry; and to develop a strategic approach to tagging that would assist in providing appropriate advice to management and industry, given the regional approach to the fishery’s regulation.

Tagging of western rock lobsters, using “spaghetti” tags in a dorsal or ventral (or both) position, has been undertaken opportunistically for many years but this report is concerned with data collected from 1988 to 1996.  Most recaptures of tagged lobsters were made during the first commercial season after release (approximately 75%), however, recaptures did occur for up to five seasons post-release. 

Keywords: Western rock lobster, Panulirus cygnus, tagging, migration, growth, mortality.

The very high levels of exploitation in the western rock lobster fishery have resulted in the introduction of regional or zone-specific management arrangements in recent years. This is a permanent departure from an holistic approach to the fishery’s regulation.  A detailed knowledge of regional variations in the growth, movement and mortality of the lobsters is required to support the models assessing regional management options.

A need was identified to supplement the Fisheries Western Australia, Research Division’s resources to enable the full analysis of existing tagging data in terms of growth, movements and mortality; to undertake tagging in shallow water to assist in addressing specific management issues; to improve the level of tag recapture information from industry; and to develop a strategic approach to tagging that would assist in providing appropriate advice to management and industry, given the regional approach to the fishery’s regulation.

Tagging of western rock lobsters, using “spaghetti” tags in a dorsal or ventral (or both) position, has been undertaken opportunistically for many years but this report is concerned with data collected from 1988 to 1996.  Most recaptures of tagged lobsters were made during the first commercial season after release (approximately 75%), however, recaptures did occur for up to five seasons post-release. 

Keywords: Western rock lobster, Panulirus cygnus, tagging, migration, growth, mortality.

The very high levels of exploitation in the western rock lobster fishery have resulted in the introduction of regional or zone-specific management arrangements in recent years. This is a permanent departure from an holistic approach to the fishery’s regulation.  A detailed knowledge of regional variations in the growth, movement and mortality of the lobsters is required to support the models assessing regional management options.

A need was identified to supplement the Fisheries Western Australia, Research Division’s resources to enable the full analysis of existing tagging data in terms of growth, movements and mortality; to undertake tagging in shallow water to assist in addressing specific management issues; to improve the level of tag recapture information from industry; and to develop a strategic approach to tagging that would assist in providing appropriate advice to management and industry, given the regional approach to the fishery’s regulation.

Tagging of western rock lobsters, using “spaghetti” tags in a dorsal or ventral (or both) position, has been undertaken opportunistically for many years but this report is concerned with data collected from 1988 to 1996.  Most recaptures of tagged lobsters were made during the first commercial season after release (approximately 75%), however, recaptures did occur for up to five seasons post-release. 

Keywords: Western rock lobster, Panulirus cygnus, tagging, migration, growth, mortality.

The very high levels of exploitation in the western rock lobster fishery have resulted in the introduction of regional or zone-specific management arrangements in recent years. This is a permanent departure from an holistic approach to the fishery’s regulation.  A detailed knowledge of regional variations in the growth, movement and mortality of the lobsters is required to support the models assessing regional management options.

A need was identified to supplement the Fisheries Western Australia, Research Division’s resources to enable the full analysis of existing tagging data in terms of growth, movements and mortality; to undertake tagging in shallow water to assist in addressing specific management issues; to improve the level of tag recapture information from industry; and to develop a strategic approach to tagging that would assist in providing appropriate advice to management and industry, given the regional approach to the fishery’s regulation.

Tagging of western rock lobsters, using “spaghetti” tags in a dorsal or ventral (or both) position, has been undertaken opportunistically for many years but this report is concerned with data collected from 1988 to 1996.  Most recaptures of tagged lobsters were made during the first commercial season after release (approximately 75%), however, recaptures did occur for up to five seasons post-release. 

Keywords: Western rock lobster, Panulirus cygnus, tagging, migration, growth, mortality.

The very high levels of exploitation in the western rock lobster fishery have resulted in the introduction of regional or zone-specific management arrangements in recent years. This is a permanent departure from an holistic approach to the fishery’s regulation.  A detailed knowledge of regional variations in the growth, movement and mortality of the lobsters is required to support the models assessing regional management options.

A need was identified to supplement the Fisheries Western Australia, Research Division’s resources to enable the full analysis of existing tagging data in terms of growth, movements and mortality; to undertake tagging in shallow water to assist in addressing specific management issues; to improve the level of tag recapture information from industry; and to develop a strategic approach to tagging that would assist in providing appropriate advice to management and industry, given the regional approach to the fishery’s regulation.

Tagging of western rock lobsters, using “spaghetti” tags in a dorsal or ventral (or both) position, has been undertaken opportunistically for many years but this report is concerned with data collected from 1988 to 1996.  Most recaptures of tagged lobsters were made during the first commercial season after release (approximately 75%), however, recaptures did occur for up to five seasons post-release. 

Keywords: Western rock lobster, Panulirus cygnus, tagging, migration, growth, mortality.

The very high levels of exploitation in the western rock lobster fishery have resulted in the introduction of regional or zone-specific management arrangements in recent years. This is a permanent departure from an holistic approach to the fishery’s regulation.  A detailed knowledge of regional variations in the growth, movement and mortality of the lobsters is required to support the models assessing regional management options.

A need was identified to supplement the Fisheries Western Australia, Research Division’s resources to enable the full analysis of existing tagging data in terms of growth, movements and mortality; to undertake tagging in shallow water to assist in addressing specific management issues; to improve the level of tag recapture information from industry; and to develop a strategic approach to tagging that would assist in providing appropriate advice to management and industry, given the regional approach to the fishery’s regulation.

Tagging of western rock lobsters, using “spaghetti” tags in a dorsal or ventral (or both) position, has been undertaken opportunistically for many years but this report is concerned with data collected from 1988 to 1996.  Most recaptures of tagged lobsters were made during the first commercial season after release (approximately 75%), however, recaptures did occur for up to five seasons post-release. 

Keywords: Western rock lobster, Panulirus cygnus, tagging, migration, growth, mortality.

The very high levels of exploitation in the western rock lobster fishery have resulted in the introduction of regional or zone-specific management arrangements in recent years. This is a permanent departure from an holistic approach to the fishery’s regulation.  A detailed knowledge of regional variations in the growth, movement and mortality of the lobsters is required to support the models assessing regional management options.

A need was identified to supplement the Fisheries Western Australia, Research Division’s resources to enable the full analysis of existing tagging data in terms of growth, movements and mortality; to undertake tagging in shallow water to assist in addressing specific management issues; to improve the level of tag recapture information from industry; and to develop a strategic approach to tagging that would assist in providing appropriate advice to management and industry, given the regional approach to the fishery’s regulation.

Tagging of western rock lobsters, using “spaghetti” tags in a dorsal or ventral (or both) position, has been undertaken opportunistically for many years but this report is concerned with data collected from 1988 to 1996.  Most recaptures of tagged lobsters were made during the first commercial season after release (approximately 75%), however, recaptures did occur for up to five seasons post-release. 

Keywords: Western rock lobster, Panulirus cygnus, tagging, migration, growth, mortality.

The very high levels of exploitation in the western rock lobster fishery have resulted in the introduction of regional or zone-specific management arrangements in recent years. This is a permanent departure from an holistic approach to the fishery’s regulation.  A detailed knowledge of regional variations in the growth, movement and mortality of the lobsters is required to support the models assessing regional management options.

A need was identified to supplement the Fisheries Western Australia, Research Division’s resources to enable the full analysis of existing tagging data in terms of growth, movements and mortality; to undertake tagging in shallow water to assist in addressing specific management issues; to improve the level of tag recapture information from industry; and to develop a strategic approach to tagging that would assist in providing appropriate advice to management and industry, given the regional approach to the fishery’s regulation.

Tagging of western rock lobsters, using “spaghetti” tags in a dorsal or ventral (or both) position, has been undertaken opportunistically for many years but this report is concerned with data collected from 1988 to 1996.  Most recaptures of tagged lobsters were made during the first commercial season after release (approximately 75%), however, recaptures did occur for up to five seasons post-release. 

Keywords: Western rock lobster, Panulirus cygnus, tagging, migration, growth, mortality.

The very high levels of exploitation in the western rock lobster fishery have resulted in the introduction of regional or zone-specific management arrangements in recent years. This is a permanent departure from an holistic approach to the fishery’s regulation.  A detailed knowledge of regional variations in the growth, movement and mortality of the lobsters is required to support the models assessing regional management options.

A need was identified to supplement the Fisheries Western Australia, Research Division’s resources to enable the full analysis of existing tagging data in terms of growth, movements and mortality; to undertake tagging in shallow water to assist in addressing specific management issues; to improve the level of tag recapture information from industry; and to develop a strategic approach to tagging that would assist in providing appropriate advice to management and industry, given the regional approach to the fishery’s regulation.

Tagging of western rock lobsters, using “spaghetti” tags in a dorsal or ventral (or both) position, has been undertaken opportunistically for many years but this report is concerned with data collected from 1988 to 1996.  Most recaptures of tagged lobsters were made during the first commercial season after release (approximately 75%), however, recaptures did occur for up to five seasons post-release. 

Keywords: Western rock lobster, Panulirus cygnus, tagging, migration, growth, mortality.

The very high levels of exploitation in the western rock lobster fishery have resulted in the introduction of regional or zone-specific management arrangements in recent years. This is a permanent departure from an holistic approach to the fishery’s regulation.  A detailed knowledge of regional variations in the growth, movement and mortality of the lobsters is required to support the models assessing regional management options.

A need was identified to supplement the Fisheries Western Australia, Research Division’s resources to enable the full analysis of existing tagging data in terms of growth, movements and mortality; to undertake tagging in shallow water to assist in addressing specific management issues; to improve the level of tag recapture information from industry; and to develop a strategic approach to tagging that would assist in providing appropriate advice to management and industry, given the regional approach to the fishery’s regulation.

Tagging of western rock lobsters, using “spaghetti” tags in a dorsal or ventral (or both) position, has been undertaken opportunistically for many years but this report is concerned with data collected from 1988 to 1996.  Most recaptures of tagged lobsters were made during the first commercial season after release (approximately 75%), however, recaptures did occur for up to five seasons post-release. 

Keywords: Western rock lobster, Panulirus cygnus, tagging, migration, growth, mortality.

The very high levels of exploitation in the western rock lobster fishery have resulted in the introduction of regional or zone-specific management arrangements in recent years. This is a permanent departure from an holistic approach to the fishery’s regulation.  A detailed knowledge of regional variations in the growth, movement and mortality of the lobsters is required to support the models assessing regional management options.

A need was identified to supplement the Fisheries Western Australia, Research Division’s resources to enable the full analysis of existing tagging data in terms of growth, movements and mortality; to undertake tagging in shallow water to assist in addressing specific management issues; to improve the level of tag recapture information from industry; and to develop a strategic approach to tagging that would assist in providing appropriate advice to management and industry, given the regional approach to the fishery’s regulation.

Tagging of western rock lobsters, using “spaghetti” tags in a dorsal or ventral (or both) position, has been undertaken opportunistically for many years but this report is concerned with data collected from 1988 to 1996.  Most recaptures of tagged lobsters were made during the first commercial season after release (approximately 75%), however, recaptures did occur for up to five seasons post-release. 

Keywords: Western rock lobster, Panulirus cygnus, tagging, migration, growth, mortality.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

Farmers receive higher prices per kilo for large yabbies.  Yabby farmers have reported that the majority of yabbies trapped from farm dams are below market size (< 30 g) and therefore of no economic value.  In addition, farmers also report that while dams produce large yabbies when first harvested, after a number of years the proportion of large animals gradually decreases.

To identify why yabbies in farm dams stunted and how farmers could increase the size of small yabbies the project had three main experimental areas: Research station experiments, industry farm dam recording system, and Genetics and Reproduction Laboratory.

This project has shown that population control methods to increase the proportion of marketable yabbies are required. This study has also shown that it is possible to convert yabbies below market size (< 30) to high value animals by improving feeding and management practices. The application of these results will produce larger yabbies and directly result in increased returns to farmers. In addition the increase in market-sized yabbies from farm dams will provide a higher catch rate per unit of trapping effort.  Consequently, the harvesting of yabbies from more isolated dams will become economically viable. 

Keywords:  Cherax albidus, crayfish culture, pond culture, aquaculture techniques, feeding, stocking density, reproduction, hybrid culture.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

Farmers receive higher prices per kilo for large yabbies.  Yabby farmers have reported that the majority of yabbies trapped from farm dams are below market size (< 30 g) and therefore of no economic value.  In addition, farmers also report that while dams produce large yabbies when first harvested, after a number of years the proportion of large animals gradually decreases.

To identify why yabbies in farm dams stunted and how farmers could increase the size of small yabbies the project had three main experimental areas: Research station experiments, industry farm dam recording system, and Genetics and Reproduction Laboratory.

This project has shown that population control methods to increase the proportion of marketable yabbies are required. This study has also shown that it is possible to convert yabbies below market size (< 30) to high value animals by improving feeding and management practices. The application of these results will produce larger yabbies and directly result in increased returns to farmers. In addition the increase in market-sized yabbies from farm dams will provide a higher catch rate per unit of trapping effort.  Consequently, the harvesting of yabbies from more isolated dams will become economically viable. 

Keywords:  Cherax albidus, crayfish culture, pond culture, aquaculture techniques, feeding, stocking density, reproduction, hybrid culture.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

Farmers receive higher prices per kilo for large yabbies.  Yabby farmers have reported that the majority of yabbies trapped from farm dams are below market size (< 30 g) and therefore of no economic value.  In addition, farmers also report that while dams produce large yabbies when first harvested, after a number of years the proportion of large animals gradually decreases.

To identify why yabbies in farm dams stunted and how farmers could increase the size of small yabbies the project had three main experimental areas: Research station experiments, industry farm dam recording system, and Genetics and Reproduction Laboratory.

This project has shown that population control methods to increase the proportion of marketable yabbies are required. This study has also shown that it is possible to convert yabbies below market size (< 30) to high value animals by improving feeding and management practices. The application of these results will produce larger yabbies and directly result in increased returns to farmers. In addition the increase in market-sized yabbies from farm dams will provide a higher catch rate per unit of trapping effort.  Consequently, the harvesting of yabbies from more isolated dams will become economically viable. 

Keywords:  Cherax albidus, crayfish culture, pond culture, aquaculture techniques, feeding, stocking density, reproduction, hybrid culture.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

Farmers receive higher prices per kilo for large yabbies.  Yabby farmers have reported that the majority of yabbies trapped from farm dams are below market size (< 30 g) and therefore of no economic value.  In addition, farmers also report that while dams produce large yabbies when first harvested, after a number of years the proportion of large animals gradually decreases.

To identify why yabbies in farm dams stunted and how farmers could increase the size of small yabbies the project had three main experimental areas: Research station experiments, industry farm dam recording system, and Genetics and Reproduction Laboratory.

This project has shown that population control methods to increase the proportion of marketable yabbies are required. This study has also shown that it is possible to convert yabbies below market size (< 30) to high value animals by improving feeding and management practices. The application of these results will produce larger yabbies and directly result in increased returns to farmers. In addition the increase in market-sized yabbies from farm dams will provide a higher catch rate per unit of trapping effort.  Consequently, the harvesting of yabbies from more isolated dams will become economically viable. 

Keywords:  Cherax albidus, crayfish culture, pond culture, aquaculture techniques, feeding, stocking density, reproduction, hybrid culture.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

Farmers receive higher prices per kilo for large yabbies.  Yabby farmers have reported that the majority of yabbies trapped from farm dams are below market size (< 30 g) and therefore of no economic value.  In addition, farmers also report that while dams produce large yabbies when first harvested, after a number of years the proportion of large animals gradually decreases.

To identify why yabbies in farm dams stunted and how farmers could increase the size of small yabbies the project had three main experimental areas: Research station experiments, industry farm dam recording system, and Genetics and Reproduction Laboratory.

This project has shown that population control methods to increase the proportion of marketable yabbies are required. This study has also shown that it is possible to convert yabbies below market size (< 30) to high value animals by improving feeding and management practices. The application of these results will produce larger yabbies and directly result in increased returns to farmers. In addition the increase in market-sized yabbies from farm dams will provide a higher catch rate per unit of trapping effort.  Consequently, the harvesting of yabbies from more isolated dams will become economically viable. 

Keywords:  Cherax albidus, crayfish culture, pond culture, aquaculture techniques, feeding, stocking density, reproduction, hybrid culture.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

Farmers receive higher prices per kilo for large yabbies.  Yabby farmers have reported that the majority of yabbies trapped from farm dams are below market size (< 30 g) and therefore of no economic value.  In addition, farmers also report that while dams produce large yabbies when first harvested, after a number of years the proportion of large animals gradually decreases.

To identify why yabbies in farm dams stunted and how farmers could increase the size of small yabbies the project had three main experimental areas: Research station experiments, industry farm dam recording system, and Genetics and Reproduction Laboratory.

This project has shown that population control methods to increase the proportion of marketable yabbies are required. This study has also shown that it is possible to convert yabbies below market size (< 30) to high value animals by improving feeding and management practices. The application of these results will produce larger yabbies and directly result in increased returns to farmers. In addition the increase in market-sized yabbies from farm dams will provide a higher catch rate per unit of trapping effort.  Consequently, the harvesting of yabbies from more isolated dams will become economically viable. 

Keywords:  Cherax albidus, crayfish culture, pond culture, aquaculture techniques, feeding, stocking density, reproduction, hybrid culture.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

Farmers receive higher prices per kilo for large yabbies.  Yabby farmers have reported that the majority of yabbies trapped from farm dams are below market size (< 30 g) and therefore of no economic value.  In addition, farmers also report that while dams produce large yabbies when first harvested, after a number of years the proportion of large animals gradually decreases.

To identify why yabbies in farm dams stunted and how farmers could increase the size of small yabbies the project had three main experimental areas: Research station experiments, industry farm dam recording system, and Genetics and Reproduction Laboratory.

This project has shown that population control methods to increase the proportion of marketable yabbies are required. This study has also shown that it is possible to convert yabbies below market size (< 30) to high value animals by improving feeding and management practices. The application of these results will produce larger yabbies and directly result in increased returns to farmers. In addition the increase in market-sized yabbies from farm dams will provide a higher catch rate per unit of trapping effort.  Consequently, the harvesting of yabbies from more isolated dams will become economically viable. 

Keywords:  Cherax albidus, crayfish culture, pond culture, aquaculture techniques, feeding, stocking density, reproduction, hybrid culture.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

Farmers receive higher prices per kilo for large yabbies.  Yabby farmers have reported that the majority of yabbies trapped from farm dams are below market size (< 30 g) and therefore of no economic value.  In addition, farmers also report that while dams produce large yabbies when first harvested, after a number of years the proportion of large animals gradually decreases.

To identify why yabbies in farm dams stunted and how farmers could increase the size of small yabbies the project had three main experimental areas: Research station experiments, industry farm dam recording system, and Genetics and Reproduction Laboratory.

This project has shown that population control methods to increase the proportion of marketable yabbies are required. This study has also shown that it is possible to convert yabbies below market size (< 30) to high value animals by improving feeding and management practices. The application of these results will produce larger yabbies and directly result in increased returns to farmers. In addition the increase in market-sized yabbies from farm dams will provide a higher catch rate per unit of trapping effort.  Consequently, the harvesting of yabbies from more isolated dams will become economically viable. 

Keywords:  Cherax albidus, crayfish culture, pond culture, aquaculture techniques, feeding, stocking density, reproduction, hybrid culture.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

Farmers receive higher prices per kilo for large yabbies.  Yabby farmers have reported that the majority of yabbies trapped from farm dams are below market size (< 30 g) and therefore of no economic value.  In addition, farmers also report that while dams produce large yabbies when first harvested, after a number of years the proportion of large animals gradually decreases.

To identify why yabbies in farm dams stunted and how farmers could increase the size of small yabbies the project had three main experimental areas: Research station experiments, industry farm dam recording system, and Genetics and Reproduction Laboratory.

This project has shown that population control methods to increase the proportion of marketable yabbies are required. This study has also shown that it is possible to convert yabbies below market size (< 30) to high value animals by improving feeding and management practices. The application of these results will produce larger yabbies and directly result in increased returns to farmers. In addition the increase in market-sized yabbies from farm dams will provide a higher catch rate per unit of trapping effort.  Consequently, the harvesting of yabbies from more isolated dams will become economically viable. 

Keywords:  Cherax albidus, crayfish culture, pond culture, aquaculture techniques, feeding, stocking density, reproduction, hybrid culture.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

Farmers receive higher prices per kilo for large yabbies.  Yabby farmers have reported that the majority of yabbies trapped from farm dams are below market size (< 30 g) and therefore of no economic value.  In addition, farmers also report that while dams produce large yabbies when first harvested, after a number of years the proportion of large animals gradually decreases.

To identify why yabbies in farm dams stunted and how farmers could increase the size of small yabbies the project had three main experimental areas: Research station experiments, industry farm dam recording system, and Genetics and Reproduction Laboratory.

This project has shown that population control methods to increase the proportion of marketable yabbies are required. This study has also shown that it is possible to convert yabbies below market size (< 30) to high value animals by improving feeding and management practices. The application of these results will produce larger yabbies and directly result in increased returns to farmers. In addition the increase in market-sized yabbies from farm dams will provide a higher catch rate per unit of trapping effort.  Consequently, the harvesting of yabbies from more isolated dams will become economically viable. 

Keywords:  Cherax albidus, crayfish culture, pond culture, aquaculture techniques, feeding, stocking density, reproduction, hybrid culture.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

Farmers receive higher prices per kilo for large yabbies.  Yabby farmers have reported that the majority of yabbies trapped from farm dams are below market size (< 30 g) and therefore of no economic value.  In addition, farmers also report that while dams produce large yabbies when first harvested, after a number of years the proportion of large animals gradually decreases.

To identify why yabbies in farm dams stunted and how farmers could increase the size of small yabbies the project had three main experimental areas: Research station experiments, industry farm dam recording system, and Genetics and Reproduction Laboratory.

This project has shown that population control methods to increase the proportion of marketable yabbies are required. This study has also shown that it is possible to convert yabbies below market size (< 30) to high value animals by improving feeding and management practices. The application of these results will produce larger yabbies and directly result in increased returns to farmers. In addition the increase in market-sized yabbies from farm dams will provide a higher catch rate per unit of trapping effort.  Consequently, the harvesting of yabbies from more isolated dams will become economically viable. 

Keywords:  Cherax albidus, crayfish culture, pond culture, aquaculture techniques, feeding, stocking density, reproduction, hybrid culture.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

Farmers receive higher prices per kilo for large yabbies.  Yabby farmers have reported that the majority of yabbies trapped from farm dams are below market size (< 30 g) and therefore of no economic value.  In addition, farmers also report that while dams produce large yabbies when first harvested, after a number of years the proportion of large animals gradually decreases.

To identify why yabbies in farm dams stunted and how farmers could increase the size of small yabbies the project had three main experimental areas: Research station experiments, industry farm dam recording system, and Genetics and Reproduction Laboratory.

This project has shown that population control methods to increase the proportion of marketable yabbies are required. This study has also shown that it is possible to convert yabbies below market size (< 30) to high value animals by improving feeding and management practices. The application of these results will produce larger yabbies and directly result in increased returns to farmers. In addition the increase in market-sized yabbies from farm dams will provide a higher catch rate per unit of trapping effort.  Consequently, the harvesting of yabbies from more isolated dams will become economically viable. 

Keywords:  Cherax albidus, crayfish culture, pond culture, aquaculture techniques, feeding, stocking density, reproduction, hybrid culture.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

Farmers receive higher prices per kilo for large yabbies.  Yabby farmers have reported that the majority of yabbies trapped from farm dams are below market size (< 30 g) and therefore of no economic value.  In addition, farmers also report that while dams produce large yabbies when first harvested, after a number of years the proportion of large animals gradually decreases.

To identify why yabbies in farm dams stunted and how farmers could increase the size of small yabbies the project had three main experimental areas: Research station experiments, industry farm dam recording system, and Genetics and Reproduction Laboratory.

This project has shown that population control methods to increase the proportion of marketable yabbies are required. This study has also shown that it is possible to convert yabbies below market size (< 30) to high value animals by improving feeding and management practices. The application of these results will produce larger yabbies and directly result in increased returns to farmers. In addition the increase in market-sized yabbies from farm dams will provide a higher catch rate per unit of trapping effort.  Consequently, the harvesting of yabbies from more isolated dams will become economically viable. 

Keywords:  Cherax albidus, crayfish culture, pond culture, aquaculture techniques, feeding, stocking density, reproduction, hybrid culture.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

Farmers receive higher prices per kilo for large yabbies.  Yabby farmers have reported that the majority of yabbies trapped from farm dams are below market size (< 30 g) and therefore of no economic value.  In addition, farmers also report that while dams produce large yabbies when first harvested, after a number of years the proportion of large animals gradually decreases.

To identify why yabbies in farm dams stunted and how farmers could increase the size of small yabbies the project had three main experimental areas: Research station experiments, industry farm dam recording system, and Genetics and Reproduction Laboratory.

This project has shown that population control methods to increase the proportion of marketable yabbies are required. This study has also shown that it is possible to convert yabbies below market size (< 30) to high value animals by improving feeding and management practices. The application of these results will produce larger yabbies and directly result in increased returns to farmers. In addition the increase in market-sized yabbies from farm dams will provide a higher catch rate per unit of trapping effort.  Consequently, the harvesting of yabbies from more isolated dams will become economically viable. 

Keywords:  Cherax albidus, crayfish culture, pond culture, aquaculture techniques, feeding, stocking density, reproduction, hybrid culture.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

Farmers receive higher prices per kilo for large yabbies.  Yabby farmers have reported that the majority of yabbies trapped from farm dams are below market size (< 30 g) and therefore of no economic value.  In addition, farmers also report that while dams produce large yabbies when first harvested, after a number of years the proportion of large animals gradually decreases.

To identify why yabbies in farm dams stunted and how farmers could increase the size of small yabbies the project had three main experimental areas: Research station experiments, industry farm dam recording system, and Genetics and Reproduction Laboratory.

This project has shown that population control methods to increase the proportion of marketable yabbies are required. This study has also shown that it is possible to convert yabbies below market size (< 30) to high value animals by improving feeding and management practices. The application of these results will produce larger yabbies and directly result in increased returns to farmers. In addition the increase in market-sized yabbies from farm dams will provide a higher catch rate per unit of trapping effort.  Consequently, the harvesting of yabbies from more isolated dams will become economically viable. 

Keywords:  Cherax albidus, crayfish culture, pond culture, aquaculture techniques, feeding, stocking density, reproduction, hybrid culture.

Yabbies are indigenous to central and eastern Australia and have created considerable aquaculture interest. Although some yabbies are produced in ponds on purpose-built farms, the vast majority of commercial aquaculture yabby production in Australia comes from trapping yabbies in farmers’ dams. This use of existing farm dams originally built to water stock has enabled rapid expansion of the industry due to low entry costs. The yabby industry currently harvests around 4,000 farm dams, with most spread throughout Western Australia’s  wheatbelt region.

The aim of this information is to assist farmers already engaged in this interesting and unusual new industry,  and to encourage more people to become involved.  Much of the information contained in this publication is the result of a research program jointly supported by Fisheries WA, FRDC, Aquaculture Development Fund (WA), the WA yabby industry, Agriculture WA and The University of Western Australia, Animal Science Group, Faculty of Agriculture. This document replaces Yabby Questions and Answers (1995) by N Morrissy, Aquainfo #1, Fisheries Department of WA.

The fishery for western lobster (Panulirus cygnus) has supported an annual catch of about  10 500 tonnes per annum over the last twenty years and is worth between $200-300 million per annum.  The fishery has been experiencing increasing exploitation rates over time and estimates in the 1990s were suggesting that the brood stock had declined to between 15-20% of unfished levels.  These low levels were considered to pose a serious risk to future recruitment and resulted in a number of management measures being introduced in the 1993/94 season aimed at raising the levels of the brood stock.

In the past, the state of egg production in the stock has been estimated using data obtained from the commercial fishery.  Data from this source can introduce possible bias, in that it is possible for fishers to avoid certain areas where there are large numbers of female animals in a breeding state and which under the new management measures are now required to be returned to the sea.  Furthermore,  the effect of increases in fishing power on commercial fishing effort due to changes in gear technology, can lead to the spawning stock index being over estimated if valid measures of the increases in effectiveness are not available.

The only way of avoiding the potential biases of using commercial data, is by conducting a sampling programme independent from commercial fishing data.   Such a pilot programme was undertaken at Fremantle and the Abrolhos Islands in 1991, was expanded to include Dongara and Jurien in 1992 and with the assistance of FRDC funding was continued and expanded to include Lancelin and Kalbarri from 1993 onwards.  The results from this survey form the basis of this report.

Commercial lobster fishing boats were chartered to do research fishing in five areas on the coast and a research vessel was assigned to the Abrolhos Islands.  Fishing took place at each of these areas over ten days during the last new moon prior to the start of the commercial fishing season in mid-November.  Standard commercial pots were set on the same GPS positions each year in areas that had previously been identified as localities which consistently yielded large numbers of spawning animals.  All lobsters caught were measured, sexed and in the case of females particular attention was paid to their reproductive state.  Environmental parameters (bottom and surface temperature, salinity, swell size) were recorded daily in each area.

Egg production indices (expressed as the mean number of eggs per pot lift) were calculated annually for each area based on the number of mature female animals in the catch.  Analysis of the results at all the coastal sites showed significant differences in egg production since the surveys first commenced.  Differences in egg production at the offshore Abrolhos Islands were not significant, but bordered on significant levels.  All the survey areas have shown an upward trend in egg production since 1993 when the management changes came into effect.

Other analyses showed that there were substantial inter-annual differences in swell size as well as surface and bottom temperatures varied significantly from year-to-year.  These environmental factors did not significantly increase or decrease the egg production indices in any one year, but the analysis did suggest that swell size has an influence on the index.

The independent spawning stock survey has been shown by this study to provide a reliable index for egg production on a regional and whole fishery basis.  The improvements in egg production indices over the relatively short time period that the survey has run, is encouraging given the recent management changes aimed at improving the brood stock.  The two year FRDC-funded extension to this project (FRDC Project 96/108) will provide increased confidence in the results.

The fishery for western lobster (Panulirus cygnus) has supported an annual catch of about  10 500 tonnes per annum over the last twenty years and is worth between $200-300 million per annum.  The fishery has been experiencing increasing exploitation rates over time and estimates in the 1990s were suggesting that the brood stock had declined to between 15-20% of unfished levels.  These low levels were considered to pose a serious risk to future recruitment and resulted in a number of management measures being introduced in the 1993/94 season aimed at raising the levels of the brood stock.

In the past, the state of egg production in the stock has been estimated using data obtained from the commercial fishery.  Data from this source can introduce possible bias, in that it is possible for fishers to avoid certain areas where there are large numbers of female animals in a breeding state and which under the new management measures are now required to be returned to the sea.  Furthermore,  the effect of increases in fishing power on commercial fishing effort due to changes in gear technology, can lead to the spawning stock index being over estimated if valid measures of the increases in effectiveness are not available.

The only way of avoiding the potential biases of using commercial data, is by conducting a sampling programme independent from commercial fishing data.   Such a pilot programme was undertaken at Fremantle and the Abrolhos Islands in 1991, was expanded to include Dongara and Jurien in 1992 and with the assistance of FRDC funding was continued and expanded to include Lancelin and Kalbarri from 1993 onwards.  The results from this survey form the basis of this report.

Commercial lobster fishing boats were chartered to do research fishing in five areas on the coast and a research vessel was assigned to the Abrolhos Islands.  Fishing took place at each of these areas over ten days during the last new moon prior to the start of the commercial fishing season in mid-November.  Standard commercial pots were set on the same GPS positions each year in areas that had previously been identified as localities which consistently yielded large numbers of spawning animals.  All lobsters caught were measured, sexed and in the case of females particular attention was paid to their reproductive state.  Environmental parameters (bottom and surface temperature, salinity, swell size) were recorded daily in each area.

Egg production indices (expressed as the mean number of eggs per pot lift) were calculated annually for each area based on the number of mature female animals in the catch.  Analysis of the results at all the coastal sites showed significant differences in egg production since the surveys first commenced.  Differences in egg production at the offshore Abrolhos Islands were not significant, but bordered on significant levels.  All the survey areas have shown an upward trend in egg production since 1993 when the management changes came into effect.

Other analyses showed that there were substantial inter-annual differences in swell size as well as surface and bottom temperatures varied significantly from year-to-year.  These environmental factors did not significantly increase or decrease the egg production indices in any one year, but the analysis did suggest that swell size has an influence on the index.

The independent spawning stock survey has been shown by this study to provide a reliable index for egg production on a regional and whole fishery basis.  The improvements in egg production indices over the relatively short time period that the survey has run, is encouraging given the recent management changes aimed at improving the brood stock.  The two year FRDC-funded extension to this project (FRDC Project 96/108) will provide increased confidence in the results.

The fishery for western lobster (Panulirus cygnus) has supported an annual catch of about  10 500 tonnes per annum over the last twenty years and is worth between $200-300 million per annum.  The fishery has been experiencing increasing exploitation rates over time and estimates in the 1990s were suggesting that the brood stock had declined to between 15-20% of unfished levels.  These low levels were considered to pose a serious risk to future recruitment and resulted in a number of management measures being introduced in the 1993/94 season aimed at raising the levels of the brood stock.

In the past, the state of egg production in the stock has been estimated using data obtained from the commercial fishery.  Data from this source can introduce possible bias, in that it is possible for fishers to avoid certain areas where there are large numbers of female animals in a breeding state and which under the new management measures are now required to be returned to the sea.  Furthermore,  the effect of increases in fishing power on commercial fishing effort due to changes in gear technology, can lead to the spawning stock index being over estimated if valid measures of the increases in effectiveness are not available.

The only way of avoiding the potential biases of using commercial data, is by conducting a sampling programme independent from commercial fishing data.   Such a pilot programme was undertaken at Fremantle and the Abrolhos Islands in 1991, was expanded to include Dongara and Jurien in 1992 and with the assistance of FRDC funding was continued and expanded to include Lancelin and Kalbarri from 1993 onwards.  The results from this survey form the basis of this report.

Commercial lobster fishing boats were chartered to do research fishing in five areas on the coast and a research vessel was assigned to the Abrolhos Islands.  Fishing took place at each of these areas over ten days during the last new moon prior to the start of the commercial fishing season in mid-November.  Standard commercial pots were set on the same GPS positions each year in areas that had previously been identified as localities which consistently yielded large numbers of spawning animals.  All lobsters caught were measured, sexed and in the case of females particular attention was paid to their reproductive state.  Environmental parameters (bottom and surface temperature, salinity, swell size) were recorded daily in each area.

Egg production indices (expressed as the mean number of eggs per pot lift) were calculated annually for each area based on the number of mature female animals in the catch.  Analysis of the results at all the coastal sites showed significant differences in egg production since the surveys first commenced.  Differences in egg production at the offshore Abrolhos Islands were not significant, but bordered on significant levels.  All the survey areas have shown an upward trend in egg production since 1993 when the management changes came into effect.

Other analyses showed that there were substantial inter-annual differences in swell size as well as surface and bottom temperatures varied significantly from year-to-year.  These environmental factors did not significantly increase or decrease the egg production indices in any one year, but the analysis did suggest that swell size has an influence on the index.

The independent spawning stock survey has been shown by this study to provide a reliable index for egg production on a regional and whole fishery basis.  The improvements in egg production indices over the relatively short time period that the survey has run, is encouraging given the recent management changes aimed at improving the brood stock.  The two year FRDC-funded extension to this project (FRDC Project 96/108) will provide increased confidence in the results.

The fishery for western lobster (Panulirus cygnus) has supported an annual catch of about  10 500 tonnes per annum over the last twenty years and is worth between $200-300 million per annum.  The fishery has been experiencing increasing exploitation rates over time and estimates in the 1990s were suggesting that the brood stock had declined to between 15-20% of unfished levels.  These low levels were considered to pose a serious risk to future recruitment and resulted in a number of management measures being introduced in the 1993/94 season aimed at raising the levels of the brood stock.

In the past, the state of egg production in the stock has been estimated using data obtained from the commercial fishery.  Data from this source can introduce possible bias, in that it is possible for fishers to avoid certain areas where there are large numbers of female animals in a breeding state and which under the new management measures are now required to be returned to the sea.  Furthermore,  the effect of increases in fishing power on commercial fishing effort due to changes in gear technology, can lead to the spawning stock index being over estimated if valid measures of the increases in effectiveness are not available.

The only way of avoiding the potential biases of using commercial data, is by conducting a sampling programme independent from commercial fishing data.   Such a pilot programme was undertaken at Fremantle and the Abrolhos Islands in 1991, was expanded to include Dongara and Jurien in 1992 and with the assistance of FRDC funding was continued and expanded to include Lancelin and Kalbarri from 1993 onwards.  The results from this survey form the basis of this report.

Commercial lobster fishing boats were chartered to do research fishing in five areas on the coast and a research vessel was assigned to the Abrolhos Islands.  Fishing took place at each of these areas over ten days during the last new moon prior to the start of the commercial fishing season in mid-November.  Standard commercial pots were set on the same GPS positions each year in areas that had previously been identified as localities which consistently yielded large numbers of spawning animals.  All lobsters caught were measured, sexed and in the case of females particular attention was paid to their reproductive state.  Environmental parameters (bottom and surface temperature, salinity, swell size) were recorded daily in each area.

Egg production indices (expressed as the mean number of eggs per pot lift) were calculated annually for each area based on the number of mature female animals in the catch.  Analysis of the results at all the coastal sites showed significant differences in egg production since the surveys first commenced.  Differences in egg production at the offshore Abrolhos Islands were not significant, but bordered on significant levels.  All the survey areas have shown an upward trend in egg production since 1993 when the management changes came into effect.

Other analyses showed that there were substantial inter-annual differences in swell size as well as surface and bottom temperatures varied significantly from year-to-year.  These environmental factors did not significantly increase or decrease the egg production indices in any one year, but the analysis did suggest that swell size has an influence on the index.

The independent spawning stock survey has been shown by this study to provide a reliable index for egg production on a regional and whole fishery basis.  The improvements in egg production indices over the relatively short time period that the survey has run, is encouraging given the recent management changes aimed at improving the brood stock.  The two year FRDC-funded extension to this project (FRDC Project 96/108) will provide increased confidence in the results.

The fishery for western lobster (Panulirus cygnus) has supported an annual catch of about  10 500 tonnes per annum over the last twenty years and is worth between $200-300 million per annum.  The fishery has been experiencing increasing exploitation rates over time and estimates in the 1990s were suggesting that the brood stock had declined to between 15-20% of unfished levels.  These low levels were considered to pose a serious risk to future recruitment and resulted in a number of management measures being introduced in the 1993/94 season aimed at raising the levels of the brood stock.

In the past, the state of egg production in the stock has been estimated using data obtained from the commercial fishery.  Data from this source can introduce possible bias, in that it is possible for fishers to avoid certain areas where there are large numbers of female animals in a breeding state and which under the new management measures are now required to be returned to the sea.  Furthermore,  the effect of increases in fishing power on commercial fishing effort due to changes in gear technology, can lead to the spawning stock index being over estimated if valid measures of the increases in effectiveness are not available.

The only way of avoiding the potential biases of using commercial data, is by conducting a sampling programme independent from commercial fishing data.   Such a pilot programme was undertaken at Fremantle and the Abrolhos Islands in 1991, was expanded to include Dongara and Jurien in 1992 and with the assistance of FRDC funding was continued and expanded to include Lancelin and Kalbarri from 1993 onwards.  The results from this survey form the basis of this report.

Commercial lobster fishing boats were chartered to do research fishing in five areas on the coast and a research vessel was assigned to the Abrolhos Islands.  Fishing took place at each of these areas over ten days during the last new moon prior to the start of the commercial fishing season in mid-November.  Standard commercial pots were set on the same GPS positions each year in areas that had previously been identified as localities which consistently yielded large numbers of spawning animals.  All lobsters caught were measured, sexed and in the case of females particular attention was paid to their reproductive state.  Environmental parameters (bottom and surface temperature, salinity, swell size) were recorded daily in each area.

Egg production indices (expressed as the mean number of eggs per pot lift) were calculated annually for each area based on the number of mature female animals in the catch.  Analysis of the results at all the coastal sites showed significant differences in egg production since the surveys first commenced.  Differences in egg production at the offshore Abrolhos Islands were not significant, but bordered on significant levels.  All the survey areas have shown an upward trend in egg production since 1993 when the management changes came into effect.

Other analyses showed that there were substantial inter-annual differences in swell size as well as surface and bottom temperatures varied significantly from year-to-year.  These environmental factors did not significantly increase or decrease the egg production indices in any one year, but the analysis did suggest that swell size has an influence on the index.

The independent spawning stock survey has been shown by this study to provide a reliable index for egg production on a regional and whole fishery basis.  The improvements in egg production indices over the relatively short time period that the survey has run, is encouraging given the recent management changes aimed at improving the brood stock.  The two year FRDC-funded extension to this project (FRDC Project 96/108) will provide increased confidence in the results.

The fishery for western lobster (Panulirus cygnus) has supported an annual catch of about  10 500 tonnes per annum over the last twenty years and is worth between $200-300 million per annum.  The fishery has been experiencing increasing exploitation rates over time and estimates in the 1990s were suggesting that the brood stock had declined to between 15-20% of unfished levels.  These low levels were considered to pose a serious risk to future recruitment and resulted in a number of management measures being introduced in the 1993/94 season aimed at raising the levels of the brood stock.

In the past, the state of egg production in the stock has been estimated using data obtained from the commercial fishery.  Data from this source can introduce possible bias, in that it is possible for fishers to avoid certain areas where there are large numbers of female animals in a breeding state and which under the new management measures are now required to be returned to the sea.  Furthermore,  the effect of increases in fishing power on commercial fishing effort due to changes in gear technology, can lead to the spawning stock index being over estimated if valid measures of the increases in effectiveness are not available.

The only way of avoiding the potential biases of using commercial data, is by conducting a sampling programme independent from commercial fishing data.   Such a pilot programme was undertaken at Fremantle and the Abrolhos Islands in 1991, was expanded to include Dongara and Jurien in 1992 and with the assistance of FRDC funding was continued and expanded to include Lancelin and Kalbarri from 1993 onwards.  The results from this survey form the basis of this report.

Commercial lobster fishing boats were chartered to do research fishing in five areas on the coast and a research vessel was assigned to the Abrolhos Islands.  Fishing took place at each of these areas over ten days during the last new moon prior to the start of the commercial fishing season in mid-November.  Standard commercial pots were set on the same GPS positions each year in areas that had previously been identified as localities which consistently yielded large numbers of spawning animals.  All lobsters caught were measured, sexed and in the case of females particular attention was paid to their reproductive state.  Environmental parameters (bottom and surface temperature, salinity, swell size) were recorded daily in each area.

Egg production indices (expressed as the mean number of eggs per pot lift) were calculated annually for each area based on the number of mature female animals in the catch.  Analysis of the results at all the coastal sites showed significant differences in egg production since the surveys first commenced.  Differences in egg production at the offshore Abrolhos Islands were not significant, but bordered on significant levels.  All the survey areas have shown an upward trend in egg production since 1993 when the management changes came into effect.

Other analyses showed that there were substantial inter-annual differences in swell size as well as surface and bottom temperatures varied significantly from year-to-year.  These environmental factors did not significantly increase or decrease the egg production indices in any one year, but the analysis did suggest that swell size has an influence on the index.

The independent spawning stock survey has been shown by this study to provide a reliable index for egg production on a regional and whole fishery basis.  The improvements in egg production indices over the relatively short time period that the survey has run, is encouraging given the recent management changes aimed at improving the brood stock.  The two year FRDC-funded extension to this project (FRDC Project 96/108) will provide increased confidence in the results.

The fishery for western lobster (Panulirus cygnus) has supported an annual catch of about  10 500 tonnes per annum over the last twenty years and is worth between $200-300 million per annum.  The fishery has been experiencing increasing exploitation rates over time and estimates in the 1990s were suggesting that the brood stock had declined to between 15-20% of unfished levels.  These low levels were considered to pose a serious risk to future recruitment and resulted in a number of management measures being introduced in the 1993/94 season aimed at raising the levels of the brood stock.

In the past, the state of egg production in the stock has been estimated using data obtained from the commercial fishery.  Data from this source can introduce possible bias, in that it is possible for fishers to avoid certain areas where there are large numbers of female animals in a breeding state and which under the new management measures are now required to be returned to the sea.  Furthermore,  the effect of increases in fishing power on commercial fishing effort due to changes in gear technology, can lead to the spawning stock index being over estimated if valid measures of the increases in effectiveness are not available.

The only way of avoiding the potential biases of using commercial data, is by conducting a sampling programme independent from commercial fishing data.   Such a pilot programme was undertaken at Fremantle and the Abrolhos Islands in 1991, was expanded to include Dongara and Jurien in 1992 and with the assistance of FRDC funding was continued and expanded to include Lancelin and Kalbarri from 1993 onwards.  The results from this survey form the basis of this report.

Commercial lobster fishing boats were chartered to do research fishing in five areas on the coast and a research vessel was assigned to the Abrolhos Islands.  Fishing took place at each of these areas over ten days during the last new moon prior to the start of the commercial fishing season in mid-November.  Standard commercial pots were set on the same GPS positions each year in areas that had previously been identified as localities which consistently yielded large numbers of spawning animals.  All lobsters caught were measured, sexed and in the case of females particular attention was paid to their reproductive state.  Environmental parameters (bottom and surface temperature, salinity, swell size) were recorded daily in each area.

Egg production indices (expressed as the mean number of eggs per pot lift) were calculated annually for each area based on the number of mature female animals in the catch.  Analysis of the results at all the coastal sites showed significant differences in egg production since the surveys first commenced.  Differences in egg production at the offshore Abrolhos Islands were not significant, but bordered on significant levels.  All the survey areas have shown an upward trend in egg production since 1993 when the management changes came into effect.

Other analyses showed that there were substantial inter-annual differences in swell size as well as surface and bottom temperatures varied significantly from year-to-year.  These environmental factors did not significantly increase or decrease the egg production indices in any one year, but the analysis did suggest that swell size has an influence on the index.

The independent spawning stock survey has been shown by this study to provide a reliable index for egg production on a regional and whole fishery basis.  The improvements in egg production indices over the relatively short time period that the survey has run, is encouraging given the recent management changes aimed at improving the brood stock.  The two year FRDC-funded extension to this project (FRDC Project 96/108) will provide increased confidence in the results.

The fishery for western lobster (Panulirus cygnus) has supported an annual catch of about  10 500 tonnes per annum over the last twenty years and is worth between $200-300 million per annum.  The fishery has been experiencing increasing exploitation rates over time and estimates in the 1990s were suggesting that the brood stock had declined to between 15-20% of unfished levels.  These low levels were considered to pose a serious risk to future recruitment and resulted in a number of management measures being introduced in the 1993/94 season aimed at raising the levels of the brood stock.

In the past, the state of egg production in the stock has been estimated using data obtained from the commercial fishery.  Data from this source can introduce possible bias, in that it is possible for fishers to avoid certain areas where there are large numbers of female animals in a breeding state and which under the new management measures are now required to be returned to the sea.  Furthermore,  the effect of increases in fishing power on commercial fishing effort due to changes in gear technology, can lead to the spawning stock index being over estimated if valid measures of the increases in effectiveness are not available.

The only way of avoiding the potential biases of using commercial data, is by conducting a sampling programme independent from commercial fishing data.   Such a pilot programme was undertaken at Fremantle and the Abrolhos Islands in 1991, was expanded to include Dongara and Jurien in 1992 and with the assistance of FRDC funding was continued and expanded to include Lancelin and Kalbarri from 1993 onwards.  The results from this survey form the basis of this report.

Commercial lobster fishing boats were chartered to do research fishing in five areas on the coast and a research vessel was assigned to the Abrolhos Islands.  Fishing took place at each of these areas over ten days during the last new moon prior to the start of the commercial fishing season in mid-November.  Standard commercial pots were set on the same GPS positions each year in areas that had previously been identified as localities which consistently yielded large numbers of spawning animals.  All lobsters caught were measured, sexed and in the case of females particular attention was paid to their reproductive state.  Environmental parameters (bottom and surface temperature, salinity, swell size) were recorded daily in each area.

Egg production indices (expressed as the mean number of eggs per pot lift) were calculated annually for each area based on the number of mature female animals in the catch.  Analysis of the results at all the coastal sites showed significant differences in egg production since the surveys first commenced.  Differences in egg production at the offshore Abrolhos Islands were not significant, but bordered on significant levels.  All the survey areas have shown an upward trend in egg production since 1993 when the management changes came into effect.

Other analyses showed that there were substantial inter-annual differences in swell size as well as surface and bottom temperatures varied significantly from year-to-year.  These environmental factors did not significantly increase or decrease the egg production indices in any one year, but the analysis did suggest that swell size has an influence on the index.

The independent spawning stock survey has been shown by this study to provide a reliable index for egg production on a regional and whole fishery basis.  The improvements in egg production indices over the relatively short time period that the survey has run, is encouraging given the recent management changes aimed at improving the brood stock.  The two year FRDC-funded extension to this project (FRDC Project 96/108) will provide increased confidence in the results.

The fishery for western lobster (Panulirus cygnus) has supported an annual catch of about  10 500 tonnes per annum over the last twenty years and is worth between $200-300 million per annum.  The fishery has been experiencing increasing exploitation rates over time and estimates in the 1990s were suggesting that the brood stock had declined to between 15-20% of unfished levels.  These low levels were considered to pose a serious risk to future recruitment and resulted in a number of management measures being introduced in the 1993/94 season aimed at raising the levels of the brood stock.

In the past, the state of egg production in the stock has been estimated using data obtained from the commercial fishery.  Data from this source can introduce possible bias, in that it is possible for fishers to avoid certain areas where there are large numbers of female animals in a breeding state and which under the new management measures are now required to be returned to the sea.  Furthermore,  the effect of increases in fishing power on commercial fishing effort due to changes in gear technology, can lead to the spawning stock index being over estimated if valid measures of the increases in effectiveness are not available.

The only way of avoiding the potential biases of using commercial data, is by conducting a sampling programme independent from commercial fishing data.   Such a pilot programme was undertaken at Fremantle and the Abrolhos Islands in 1991, was expanded to include Dongara and Jurien in 1992 and with the assistance of FRDC funding was continued and expanded to include Lancelin and Kalbarri from 1993 onwards.  The results from this survey form the basis of this report.

Commercial lobster fishing boats were chartered to do research fishing in five areas on the coast and a research vessel was assigned to the Abrolhos Islands.  Fishing took place at each of these areas over ten days during the last new moon prior to the start of the commercial fishing season in mid-November.  Standard commercial pots were set on the same GPS positions each year in areas that had previously been identified as localities which consistently yielded large numbers of spawning animals.  All lobsters caught were measured, sexed and in the case of females particular attention was paid to their reproductive state.  Environmental parameters (bottom and surface temperature, salinity, swell size) were recorded daily in each area.

Egg production indices (expressed as the mean number of eggs per pot lift) were calculated annually for each area based on the number of mature female animals in the catch.  Analysis of the results at all the coastal sites showed significant differences in egg production since the surveys first commenced.  Differences in egg production at the offshore Abrolhos Islands were not significant, but bordered on significant levels.  All the survey areas have shown an upward trend in egg production since 1993 when the management changes came into effect.

Other analyses showed that there were substantial inter-annual differences in swell size as well as surface and bottom temperatures varied significantly from year-to-year.  These environmental factors did not significantly increase or decrease the egg production indices in any one year, but the analysis did suggest that swell size has an influence on the index.

The independent spawning stock survey has been shown by this study to provide a reliable index for egg production on a regional and whole fishery basis.  The improvements in egg production indices over the relatively short time period that the survey has run, is encouraging given the recent management changes aimed at improving the brood stock.  The two year FRDC-funded extension to this project (FRDC Project 96/108) will provide increased confidence in the results.

The fishery for western lobster (Panulirus cygnus) has supported an annual catch of about  10 500 tonnes per annum over the last twenty years and is worth between $200-300 million per annum.  The fishery has been experiencing increasing exploitation rates over time and estimates in the 1990s were suggesting that the brood stock had declined to between 15-20% of unfished levels.  These low levels were considered to pose a serious risk to future recruitment and resulted in a number of management measures being introduced in the 1993/94 season aimed at raising the levels of the brood stock.

In the past, the state of egg production in the stock has been estimated using data obtained from the commercial fishery.  Data from this source can introduce possible bias, in that it is possible for fishers to avoid certain areas where there are large numbers of female animals in a breeding state and which under the new management measures are now required to be returned to the sea.  Furthermore,  the effect of increases in fishing power on commercial fishing effort due to changes in gear technology, can lead to the spawning stock index being over estimated if valid measures of the increases in effectiveness are not available.

The only way of avoiding the potential biases of using commercial data, is by conducting a sampling programme independent from commercial fishing data.   Such a pilot programme was undertaken at Fremantle and the Abrolhos Islands in 1991, was expanded to include Dongara and Jurien in 1992 and with the assistance of FRDC funding was continued and expanded to include Lancelin and Kalbarri from 1993 onwards.  The results from this survey form the basis of this report.

Commercial lobster fishing boats were chartered to do research fishing in five areas on the coast and a research vessel was assigned to the Abrolhos Islands.  Fishing took place at each of these areas over ten days during the last new moon prior to the start of the commercial fishing season in mid-November.  Standard commercial pots were set on the same GPS positions each year in areas that had previously been identified as localities which consistently yielded large numbers of spawning animals.  All lobsters caught were measured, sexed and in the case of females particular attention was paid to their reproductive state.  Environmental parameters (bottom and surface temperature, salinity, swell size) were recorded daily in each area.

Egg production indices (expressed as the mean number of eggs per pot lift) were calculated annually for each area based on the number of mature female animals in the catch.  Analysis of the results at all the coastal sites showed significant differences in egg production since the surveys first commenced.  Differences in egg production at the offshore Abrolhos Islands were not significant, but bordered on significant levels.  All the survey areas have shown an upward trend in egg production since 1993 when the management changes came into effect.

Other analyses showed that there were substantial inter-annual differences in swell size as well as surface and bottom temperatures varied significantly from year-to-year.  These environmental factors did not significantly increase or decrease the egg production indices in any one year, but the analysis did suggest that swell size has an influence on the index.

The independent spawning stock survey has been shown by this study to provide a reliable index for egg production on a regional and whole fishery basis.  The improvements in egg production indices over the relatively short time period that the survey has run, is encouraging given the recent management changes aimed at improving the brood stock.  The two year FRDC-funded extension to this project (FRDC Project 96/108) will provide increased confidence in the results.

The fishery for western lobster (Panulirus cygnus) has supported an annual catch of about  10 500 tonnes per annum over the last twenty years and is worth between $200-300 million per annum.  The fishery has been experiencing increasing exploitation rates over time and estimates in the 1990s were suggesting that the brood stock had declined to between 15-20% of unfished levels.  These low levels were considered to pose a serious risk to future recruitment and resulted in a number of management measures being introduced in the 1993/94 season aimed at raising the levels of the brood stock.

In the past, the state of egg production in the stock has been estimated using data obtained from the commercial fishery.  Data from this source can introduce possible bias, in that it is possible for fishers to avoid certain areas where there are large numbers of female animals in a breeding state and which under the new management measures are now required to be returned to the sea.  Furthermore,  the effect of increases in fishing power on commercial fishing effort due to changes in gear technology, can lead to the spawning stock index being over estimated if valid measures of the increases in effectiveness are not available.

The only way of avoiding the potential biases of using commercial data, is by conducting a sampling programme independent from commercial fishing data.   Such a pilot programme was undertaken at Fremantle and the Abrolhos Islands in 1991, was expanded to include Dongara and Jurien in 1992 and with the assistance of FRDC funding was continued and expanded to include Lancelin and Kalbarri from 1993 onwards.  The results from this survey form the basis of this report.

Commercial lobster fishing boats were chartered to do research fishing in five areas on the coast and a research vessel was assigned to the Abrolhos Islands.  Fishing took place at each of these areas over ten days during the last new moon prior to the start of the commercial fishing season in mid-November.  Standard commercial pots were set on the same GPS positions each year in areas that had previously been identified as localities which consistently yielded large numbers of spawning animals.  All lobsters caught were measured, sexed and in the case of females particular attention was paid to their reproductive state.  Environmental parameters (bottom and surface temperature, salinity, swell size) were recorded daily in each area.

Egg production indices (expressed as the mean number of eggs per pot lift) were calculated annually for each area based on the number of mature female animals in the catch.  Analysis of the results at all the coastal sites showed significant differences in egg production since the surveys first commenced.  Differences in egg production at the offshore Abrolhos Islands were not significant, but bordered on significant levels.  All the survey areas have shown an upward trend in egg production since 1993 when the management changes came into effect.

Other analyses showed that there were substantial inter-annual differences in swell size as well as surface and bottom temperatures varied significantly from year-to-year.  These environmental factors did not significantly increase or decrease the egg production indices in any one year, but the analysis did suggest that swell size has an influence on the index.

The independent spawning stock survey has been shown by this study to provide a reliable index for egg production on a regional and whole fishery basis.  The improvements in egg production indices over the relatively short time period that the survey has run, is encouraging given the recent management changes aimed at improving the brood stock.  The two year FRDC-funded extension to this project (FRDC Project 96/108) will provide increased confidence in the results.

The fishery for western lobster (Panulirus cygnus) has supported an annual catch of about  10 500 tonnes per annum over the last twenty years and is worth between $200-300 million per annum.  The fishery has been experiencing increasing exploitation rates over time and estimates in the 1990s were suggesting that the brood stock had declined to between 15-20% of unfished levels.  These low levels were considered to pose a serious risk to future recruitment and resulted in a number of management measures being introduced in the 1993/94 season aimed at raising the levels of the brood stock.

In the past, the state of egg production in the stock has been estimated using data obtained from the commercial fishery.  Data from this source can introduce possible bias, in that it is possible for fishers to avoid certain areas where there are large numbers of female animals in a breeding state and which under the new management measures are now required to be returned to the sea.  Furthermore,  the effect of increases in fishing power on commercial fishing effort due to changes in gear technology, can lead to the spawning stock index being over estimated if valid measures of the increases in effectiveness are not available.

The only way of avoiding the potential biases of using commercial data, is by conducting a sampling programme independent from commercial fishing data.   Such a pilot programme was undertaken at Fremantle and the Abrolhos Islands in 1991, was expanded to include Dongara and Jurien in 1992 and with the assistance of FRDC funding was continued and expanded to include Lancelin and Kalbarri from 1993 onwards.  The results from this survey form the basis of this report.

Commercial lobster fishing boats were chartered to do research fishing in five areas on the coast and a research vessel was assigned to the Abrolhos Islands.  Fishing took place at each of these areas over ten days during the last new moon prior to the start of the commercial fishing season in mid-November.  Standard commercial pots were set on the same GPS positions each year in areas that had previously been identified as localities which consistently yielded large numbers of spawning animals.  All lobsters caught were measured, sexed and in the case of females particular attention was paid to their reproductive state.  Environmental parameters (bottom and surface temperature, salinity, swell size) were recorded daily in each area.

Egg production indices (expressed as the mean number of eggs per pot lift) were calculated annually for each area based on the number of mature female animals in the catch.  Analysis of the results at all the coastal sites showed significant differences in egg production since the surveys first commenced.  Differences in egg production at the offshore Abrolhos Islands were not significant, but bordered on significant levels.  All the survey areas have shown an upward trend in egg production since 1993 when the management changes came into effect.

Other analyses showed that there were substantial inter-annual differences in swell size as well as surface and bottom temperatures varied significantly from year-to-year.  These environmental factors did not significantly increase or decrease the egg production indices in any one year, but the analysis did suggest that swell size has an influence on the index.

The independent spawning stock survey has been shown by this study to provide a reliable index for egg production on a regional and whole fishery basis.  The improvements in egg production indices over the relatively short time period that the survey has run, is encouraging given the recent management changes aimed at improving the brood stock.  The two year FRDC-funded extension to this project (FRDC Project 96/108) will provide increased confidence in the results.

The fishery for western lobster (Panulirus cygnus) has supported an annual catch of about  10 500 tonnes per annum over the last twenty years and is worth between $200-300 million per annum.  The fishery has been experiencing increasing exploitation rates over time and estimates in the 1990s were suggesting that the brood stock had declined to between 15-20% of unfished levels.  These low levels were considered to pose a serious risk to future recruitment and resulted in a number of management measures being introduced in the 1993/94 season aimed at raising the levels of the brood stock.

In the past, the state of egg production in the stock has been estimated using data obtained from the commercial fishery.  Data from this source can introduce possible bias, in that it is possible for fishers to avoid certain areas where there are large numbers of female animals in a breeding state and which under the new management measures are now required to be returned to the sea.  Furthermore,  the effect of increases in fishing power on commercial fishing effort due to changes in gear technology, can lead to the spawning stock index being over estimated if valid measures of the increases in effectiveness are not available.

The only way of avoiding the potential biases of using commercial data, is by conducting a sampling programme independent from commercial fishing data.   Such a pilot programme was undertaken at Fremantle and the Abrolhos Islands in 1991, was expanded to include Dongara and Jurien in 1992 and with the assistance of FRDC funding was continued and expanded to include Lancelin and Kalbarri from 1993 onwards.  The results from this survey form the basis of this report.

Commercial lobster fishing boats were chartered to do research fishing in five areas on the coast and a research vessel was assigned to the Abrolhos Islands.  Fishing took place at each of these areas over ten days during the last new moon prior to the start of the commercial fishing season in mid-November.  Standard commercial pots were set on the same GPS positions each year in areas that had previously been identified as localities which consistently yielded large numbers of spawning animals.  All lobsters caught were measured, sexed and in the case of females particular attention was paid to their reproductive state.  Environmental parameters (bottom and surface temperature, salinity, swell size) were recorded daily in each area.

Egg production indices (expressed as the mean number of eggs per pot lift) were calculated annually for each area based on the number of mature female animals in the catch.  Analysis of the results at all the coastal sites showed significant differences in egg production since the surveys first commenced.  Differences in egg production at the offshore Abrolhos Islands were not significant, but bordered on significant levels.  All the survey areas have shown an upward trend in egg production since 1993 when the management changes came into effect.

Other analyses showed that there were substantial inter-annual differences in swell size as well as surface and bottom temperatures varied significantly from year-to-year.  These environmental factors did not significantly increase or decrease the egg production indices in any one year, but the analysis did suggest that swell size has an influence on the index.

The independent spawning stock survey has been shown by this study to provide a reliable index for egg production on a regional and whole fishery basis.  The improvements in egg production indices over the relatively short time period that the survey has run, is encouraging given the recent management changes aimed at improving the brood stock.  The two year FRDC-funded extension to this project (FRDC Project 96/108) will provide increased confidence in the results.

The fishery for western lobster (Panulirus cygnus) has supported an annual catch of about  10 500 tonnes per annum over the last twenty years and is worth between $200-300 million per annum.  The fishery has been experiencing increasing exploitation rates over time and estimates in the 1990s were suggesting that the brood stock had declined to between 15-20% of unfished levels.  These low levels were considered to pose a serious risk to future recruitment and resulted in a number of management measures being introduced in the 1993/94 season aimed at raising the levels of the brood stock.

In the past, the state of egg production in the stock has been estimated using data obtained from the commercial fishery.  Data from this source can introduce possible bias, in that it is possible for fishers to avoid certain areas where there are large numbers of female animals in a breeding state and which under the new management measures are now required to be returned to the sea.  Furthermore,  the effect of increases in fishing power on commercial fishing effort due to changes in gear technology, can lead to the spawning stock index being over estimated if valid measures of the increases in effectiveness are not available.

The only way of avoiding the potential biases of using commercial data, is by conducting a sampling programme independent from commercial fishing data.   Such a pilot programme was undertaken at Fremantle and the Abrolhos Islands in 1991, was expanded to include Dongara and Jurien in 1992 and with the assistance of FRDC funding was continued and expanded to include Lancelin and Kalbarri from 1993 onwards.  The results from this survey form the basis of this report.

Commercial lobster fishing boats were chartered to do research fishing in five areas on the coast and a research vessel was assigned to the Abrolhos Islands.  Fishing took place at each of these areas over ten days during the last new moon prior to the start of the commercial fishing season in mid-November.  Standard commercial pots were set on the same GPS positions each year in areas that had previously been identified as localities which consistently yielded large numbers of spawning animals.  All lobsters caught were measured, sexed and in the case of females particular attention was paid to their reproductive state.  Environmental parameters (bottom and surface temperature, salinity, swell size) were recorded daily in each area.

Egg production indices (expressed as the mean number of eggs per pot lift) were calculated annually for each area based on the number of mature female animals in the catch.  Analysis of the results at all the coastal sites showed significant differences in egg production since the surveys first commenced.  Differences in egg production at the offshore Abrolhos Islands were not significant, but bordered on significant levels.  All the survey areas have shown an upward trend in egg production since 1993 when the management changes came into effect.

Other analyses showed that there were substantial inter-annual differences in swell size as well as surface and bottom temperatures varied significantly from year-to-year.  These environmental factors did not significantly increase or decrease the egg production indices in any one year, but the analysis did suggest that swell size has an influence on the index.

The independent spawning stock survey has been shown by this study to provide a reliable index for egg production on a regional and whole fishery basis.  The improvements in egg production indices over the relatively short time period that the survey has run, is encouraging given the recent management changes aimed at improving the brood stock.  The two year FRDC-funded extension to this project (FRDC Project 96/108) will provide increased confidence in the results.

The fishery for western lobster (Panulirus cygnus) has supported an annual catch of about  10 500 tonnes per annum over the last twenty years and is worth between $200-300 million per annum.  The fishery has been experiencing increasing exploitation rates over time and estimates in the 1990s were suggesting that the brood stock had declined to between 15-20% of unfished levels.  These low levels were considered to pose a serious risk to future recruitment and resulted in a number of management measures being introduced in the 1993/94 season aimed at raising the levels of the brood stock.

In the past, the state of egg production in the stock has been estimated using data obtained from the commercial fishery.  Data from this source can introduce possible bias, in that it is possible for fishers to avoid certain areas where there are large numbers of female animals in a breeding state and which under the new management measures are now required to be returned to the sea.  Furthermore,  the effect of increases in fishing power on commercial fishing effort due to changes in gear technology, can lead to the spawning stock index being over estimated if valid measures of the increases in effectiveness are not available.

The only way of avoiding the potential biases of using commercial data, is by conducting a sampling programme independent from commercial fishing data.   Such a pilot programme was undertaken at Fremantle and the Abrolhos Islands in 1991, was expanded to include Dongara and Jurien in 1992 and with the assistance of FRDC funding was continued and expanded to include Lancelin and Kalbarri from 1993 onwards.  The results from this survey form the basis of this report.

Commercial lobster fishing boats were chartered to do research fishing in five areas on the coast and a research vessel was assigned to the Abrolhos Islands.  Fishing took place at each of these areas over ten days during the last new moon prior to the start of the commercial fishing season in mid-November.  Standard commercial pots were set on the same GPS positions each year in areas that had previously been identified as localities which consistently yielded large numbers of spawning animals.  All lobsters caught were measured, sexed and in the case of females particular attention was paid to their reproductive state.  Environmental parameters (bottom and surface temperature, salinity, swell size) were recorded daily in each area.

Egg production indices (expressed as the mean number of eggs per pot lift) were calculated annually for each area based on the number of mature female animals in the catch.  Analysis of the results at all the coastal sites showed significant differences in egg production since the surveys first commenced.  Differences in egg production at the offshore Abrolhos Islands were not significant, but bordered on significant levels.  All the survey areas have shown an upward trend in egg production since 1993 when the management changes came into effect.

Other analyses showed that there were substantial inter-annual differences in swell size as well as surface and bottom temperatures varied significantly from year-to-year.  These environmental factors did not significantly increase or decrease the egg production indices in any one year, but the analysis did suggest that swell size has an influence on the index.

The independent spawning stock survey has been shown by this study to provide a reliable index for egg production on a regional and whole fishery basis.  The improvements in egg production indices over the relatively short time period that the survey has run, is encouraging given the recent management changes aimed at improving the brood stock.  The two year FRDC-funded extension to this project (FRDC Project 96/108) will provide increased confidence in the results.