56,697 results

Development of an algal bloom monitoring buoy for the Australian aquaculture industry: proof of concept

Project number: 1995-085
Project Status:
Completed
Budget expenditure: $20,000.00
Principal Investigator: Gustaaf Hallegraeff
Organisation: University of Tasmania (UTAS)
Project start/end date: 23 Jan 1996 - 29 Aug 1997
Contact:
FRDC
TAGS
Sustainability
Remote Sensing
Oceanography
Fisheries Management
Electronic Monitoring

Objectives

1. To improve the sensitivity of current algal watch programmes in Tasmanian waters, designed to protect shellfish and finfish aquaculture by means of frequent microscopic plankton analyses

Final report

Author: G.M. Hallegraeff and C. Ashworth
Final Report • 1997-06-25 • 2.06 MB
1995-085-DLD.pdf

Summary

A prototype of an automatic algal monitoring buoy was developed for unattended operation in shellfish and finfish farm waters. The instrument employs novel antifouling and self-calibration strategies (subject to a provisional patent ) based on a battery-powered actuator extending into the seawater medium at 15 min intervals both a light source and a solid state sensor from a protective PVC cylinder. The optical sensor measures both ambient light and the signal from a high intensity LED light source, with separate readings being taken after travelling through an optical fibre reference path (internal standard) and after travelling through a 60 cm horizontal path of natural seawater. The optical system is suspended at 1 m depth (can be varied) from a float with the systems control and data acquisition system located above water.

Financial constraints ($20,000 FRDC budget) prevented us to also implement a radiomodem link to laboratory computer as originally planned. We are now seeking further funds to develop the instrument to a commercial stage (estimated market value per unit Aus $10,000) and extensively test its field performance under a range of environmental and algal bloom conditions.

Final Report • 1997-06-25 • 2.06 MB
1995-085-DLD.pdf

Summary

A prototype of an automatic algal monitoring buoy was developed for unattended operation in shellfish and finfish farm waters. The instrument employs novel antifouling and self-calibration strategies (subject to a provisional patent ) based on a battery-powered actuator extending into the seawater medium at 15 min intervals both a light source and a solid state sensor from a protective PVC cylinder. The optical sensor measures both ambient light and the signal from a high intensity LED light source, with separate readings being taken after travelling through an optical fibre reference path (internal standard) and after travelling through a 60 cm horizontal path of natural seawater. The optical system is suspended at 1 m depth (can be varied) from a float with the systems control and data acquisition system located above water.

Financial constraints ($20,000 FRDC budget) prevented us to also implement a radiomodem link to laboratory computer as originally planned. We are now seeking further funds to develop the instrument to a commercial stage (estimated market value per unit Aus $10,000) and extensively test its field performance under a range of environmental and algal bloom conditions.

Final Report • 1997-06-25 • 2.06 MB
1995-085-DLD.pdf

Summary

A prototype of an automatic algal monitoring buoy was developed for unattended operation in shellfish and finfish farm waters. The instrument employs novel antifouling and self-calibration strategies (subject to a provisional patent ) based on a battery-powered actuator extending into the seawater medium at 15 min intervals both a light source and a solid state sensor from a protective PVC cylinder. The optical sensor measures both ambient light and the signal from a high intensity LED light source, with separate readings being taken after travelling through an optical fibre reference path (internal standard) and after travelling through a 60 cm horizontal path of natural seawater. The optical system is suspended at 1 m depth (can be varied) from a float with the systems control and data acquisition system located above water.

Financial constraints ($20,000 FRDC budget) prevented us to also implement a radiomodem link to laboratory computer as originally planned. We are now seeking further funds to develop the instrument to a commercial stage (estimated market value per unit Aus $10,000) and extensively test its field performance under a range of environmental and algal bloom conditions.

Final Report • 1997-06-25 • 2.06 MB
1995-085-DLD.pdf

Summary

A prototype of an automatic algal monitoring buoy was developed for unattended operation in shellfish and finfish farm waters. The instrument employs novel antifouling and self-calibration strategies (subject to a provisional patent ) based on a battery-powered actuator extending into the seawater medium at 15 min intervals both a light source and a solid state sensor from a protective PVC cylinder. The optical sensor measures both ambient light and the signal from a high intensity LED light source, with separate readings being taken after travelling through an optical fibre reference path (internal standard) and after travelling through a 60 cm horizontal path of natural seawater. The optical system is suspended at 1 m depth (can be varied) from a float with the systems control and data acquisition system located above water.

Financial constraints ($20,000 FRDC budget) prevented us to also implement a radiomodem link to laboratory computer as originally planned. We are now seeking further funds to develop the instrument to a commercial stage (estimated market value per unit Aus $10,000) and extensively test its field performance under a range of environmental and algal bloom conditions.

Final Report • 1997-06-25 • 2.06 MB
1995-085-DLD.pdf

Summary

A prototype of an automatic algal monitoring buoy was developed for unattended operation in shellfish and finfish farm waters. The instrument employs novel antifouling and self-calibration strategies (subject to a provisional patent ) based on a battery-powered actuator extending into the seawater medium at 15 min intervals both a light source and a solid state sensor from a protective PVC cylinder. The optical sensor measures both ambient light and the signal from a high intensity LED light source, with separate readings being taken after travelling through an optical fibre reference path (internal standard) and after travelling through a 60 cm horizontal path of natural seawater. The optical system is suspended at 1 m depth (can be varied) from a float with the systems control and data acquisition system located above water.

Financial constraints ($20,000 FRDC budget) prevented us to also implement a radiomodem link to laboratory computer as originally planned. We are now seeking further funds to develop the instrument to a commercial stage (estimated market value per unit Aus $10,000) and extensively test its field performance under a range of environmental and algal bloom conditions.

NSW inland commercial fisheries analysis

Project number: 1994-027
Project Status:
Completed
Budget expenditure: $154,672.32
Principal Investigator: John H. Harris
Organisation: Department of Primary Industries and Regional Development (NSW)
Project start/end date: 22 Jun 1994 - 22 May 1998
Contact:
FRDC
TAGS
Stock Assessment
Fishing Effort
Biomass

Objectives

1. To show the utility of the inland commercial fisheries as a stock monitoring tool

Final report

ISBN: 0-7310-9410-7
Authors: D D Reid J H Harris and DJ Chapman
Final Report • 1998-04-03 • 3.34 MB
1994-027-DLD.pdf

Summary

The inland commercial fishery in New South Wales had a _mean annual catch of 344t over the past three decades, and is currently worth $1. 7 million per annum (1995/96 value). The commercial fishery commenced in the late 19th Century, and although production figures are available from 1883 onwards, coverage for years earlier than 1947 was very limited, with an unknown fraction of the total catch reported. The major species currently exploited by the fishery are golden perch, carp, Murray cod and freshwater yabby, while prior to 1980 redfin perch, silver perch and freshwater catfish were also significant components of the catch.

From the commencement of the commercial fishery there were resource conflicts between commercial fishers, traditional rights of the indigenous fishers, recreational fishers and a continual problem with widespread illegal fishing activities. The geographical extent of the fishery was gradually reduced to the current boundaries, which allow commercial fishing for finfish in approximately 5% of the linear measure of the inland waters of NSW.

There has been a long-established need for reliable data for the fishery, and while fishers have officially reported catches since 1947, the data have been poorly managed, and no comprehensive analysis has previously been attempted.

Final Report • 1998-04-03 • 3.34 MB
1994-027-DLD.pdf

Summary

The inland commercial fishery in New South Wales had a _mean annual catch of 344t over the past three decades, and is currently worth $1. 7 million per annum (1995/96 value). The commercial fishery commenced in the late 19th Century, and although production figures are available from 1883 onwards, coverage for years earlier than 1947 was very limited, with an unknown fraction of the total catch reported. The major species currently exploited by the fishery are golden perch, carp, Murray cod and freshwater yabby, while prior to 1980 redfin perch, silver perch and freshwater catfish were also significant components of the catch.

From the commencement of the commercial fishery there were resource conflicts between commercial fishers, traditional rights of the indigenous fishers, recreational fishers and a continual problem with widespread illegal fishing activities. The geographical extent of the fishery was gradually reduced to the current boundaries, which allow commercial fishing for finfish in approximately 5% of the linear measure of the inland waters of NSW.

There has been a long-established need for reliable data for the fishery, and while fishers have officially reported catches since 1947, the data have been poorly managed, and no comprehensive analysis has previously been attempted.

Final Report • 1998-04-03 • 3.34 MB
1994-027-DLD.pdf

Summary

The inland commercial fishery in New South Wales had a _mean annual catch of 344t over the past three decades, and is currently worth $1. 7 million per annum (1995/96 value). The commercial fishery commenced in the late 19th Century, and although production figures are available from 1883 onwards, coverage for years earlier than 1947 was very limited, with an unknown fraction of the total catch reported. The major species currently exploited by the fishery are golden perch, carp, Murray cod and freshwater yabby, while prior to 1980 redfin perch, silver perch and freshwater catfish were also significant components of the catch.

From the commencement of the commercial fishery there were resource conflicts between commercial fishers, traditional rights of the indigenous fishers, recreational fishers and a continual problem with widespread illegal fishing activities. The geographical extent of the fishery was gradually reduced to the current boundaries, which allow commercial fishing for finfish in approximately 5% of the linear measure of the inland waters of NSW.

There has been a long-established need for reliable data for the fishery, and while fishers have officially reported catches since 1947, the data have been poorly managed, and no comprehensive analysis has previously been attempted.

Final Report • 1998-04-03 • 3.34 MB
1994-027-DLD.pdf

Summary

The inland commercial fishery in New South Wales had a _mean annual catch of 344t over the past three decades, and is currently worth $1. 7 million per annum (1995/96 value). The commercial fishery commenced in the late 19th Century, and although production figures are available from 1883 onwards, coverage for years earlier than 1947 was very limited, with an unknown fraction of the total catch reported. The major species currently exploited by the fishery are golden perch, carp, Murray cod and freshwater yabby, while prior to 1980 redfin perch, silver perch and freshwater catfish were also significant components of the catch.

From the commencement of the commercial fishery there were resource conflicts between commercial fishers, traditional rights of the indigenous fishers, recreational fishers and a continual problem with widespread illegal fishing activities. The geographical extent of the fishery was gradually reduced to the current boundaries, which allow commercial fishing for finfish in approximately 5% of the linear measure of the inland waters of NSW.

There has been a long-established need for reliable data for the fishery, and while fishers have officially reported catches since 1947, the data have been poorly managed, and no comprehensive analysis has previously been attempted.

Final Report • 1998-04-03 • 3.34 MB
1994-027-DLD.pdf

Summary

The inland commercial fishery in New South Wales had a _mean annual catch of 344t over the past three decades, and is currently worth $1. 7 million per annum (1995/96 value). The commercial fishery commenced in the late 19th Century, and although production figures are available from 1883 onwards, coverage for years earlier than 1947 was very limited, with an unknown fraction of the total catch reported. The major species currently exploited by the fishery are golden perch, carp, Murray cod and freshwater yabby, while prior to 1980 redfin perch, silver perch and freshwater catfish were also significant components of the catch.

From the commencement of the commercial fishery there were resource conflicts between commercial fishers, traditional rights of the indigenous fishers, recreational fishers and a continual problem with widespread illegal fishing activities. The geographical extent of the fishery was gradually reduced to the current boundaries, which allow commercial fishing for finfish in approximately 5% of the linear measure of the inland waters of NSW.

There has been a long-established need for reliable data for the fishery, and while fishers have officially reported catches since 1947, the data have been poorly managed, and no comprehensive analysis has previously been attempted.

Aquaculture diet development subprogram - Dietary requirements and optimal feeding practices for Barramundi (Lates Calcarifer)

Project number: 1992-063
Project Status:
Completed
Budget expenditure: $250,109.14
Principal Investigator: Kevin C. Williams
Organisation: Department of Primary Industries (QLD)
Project start/end date: 11 Oct 1992 - 17 Nov 1999
Contact:
FRDC
TAGS
Nutrition
Innovation
Husbandry
Aquaculture

Objectives

1. To develop feeding strategies and diets for periods of fast growth (summer) and slow growth (winter) which optimise feed conversion and growth rate
2. To determine the appropriateness of an extruded floating pellet for feeding barramundi under commercial conditions
3. To investigate the potential for sparing of fish meal in barramundi grow-out diets using synthetic amino acids and cheaper sources of supplementary protein

Final report

Author: Kevin Williams Chris Barlow
Final Report • 1999-10-20 • 9.41 MB
1992-063-DLD.pdf

Summary

Feed is by far the single largest cost component of barramundi farming and accounts for about 35% of on-farm operating costs. Reducing feed costs by better tailoring dietary specifications to the nutrient requirements of the fish, by providing these nutrients at least cost and by adopting feeding practices that optimise productivity will greatly assist farm profitability. In Australia, barramundi are pond-reared over latitudes from 5°S to 22°S and this results in large seasonal variations in water temperature and consequently, in growth rate of the fish.

The research conducted in this project sought primarily to characterise the effect of water temperature on fish productivity and how modification of dietary nutrient specifications and/or feeding practices could assist in improving farming profitability. This entailed research to define the fish's response to changes in dietary supply of critical nutrients over a range of water temperatures. Research examining the efficacy of crystalline amino acids in diets for barramundi was carried out in a supplementary project (FRDC 95/69); research on the nutritive value of terrestrial feed ingredients and their suitability as replacements of fishmeal in diets for barramundi is reported in FRDC 93/120-04.

Final Report • 1999-10-20 • 9.41 MB
1992-063-DLD.pdf

Summary

Feed is by far the single largest cost component of barramundi farming and accounts for about 35% of on-farm operating costs. Reducing feed costs by better tailoring dietary specifications to the nutrient requirements of the fish, by providing these nutrients at least cost and by adopting feeding practices that optimise productivity will greatly assist farm profitability. In Australia, barramundi are pond-reared over latitudes from 5°S to 22°S and this results in large seasonal variations in water temperature and consequently, in growth rate of the fish.

The research conducted in this project sought primarily to characterise the effect of water temperature on fish productivity and how modification of dietary nutrient specifications and/or feeding practices could assist in improving farming profitability. This entailed research to define the fish's response to changes in dietary supply of critical nutrients over a range of water temperatures. Research examining the efficacy of crystalline amino acids in diets for barramundi was carried out in a supplementary project (FRDC 95/69); research on the nutritive value of terrestrial feed ingredients and their suitability as replacements of fishmeal in diets for barramundi is reported in FRDC 93/120-04.

Final Report • 1999-10-20 • 9.41 MB
1992-063-DLD.pdf

Summary

Feed is by far the single largest cost component of barramundi farming and accounts for about 35% of on-farm operating costs. Reducing feed costs by better tailoring dietary specifications to the nutrient requirements of the fish, by providing these nutrients at least cost and by adopting feeding practices that optimise productivity will greatly assist farm profitability. In Australia, barramundi are pond-reared over latitudes from 5°S to 22°S and this results in large seasonal variations in water temperature and consequently, in growth rate of the fish.

The research conducted in this project sought primarily to characterise the effect of water temperature on fish productivity and how modification of dietary nutrient specifications and/or feeding practices could assist in improving farming profitability. This entailed research to define the fish's response to changes in dietary supply of critical nutrients over a range of water temperatures. Research examining the efficacy of crystalline amino acids in diets for barramundi was carried out in a supplementary project (FRDC 95/69); research on the nutritive value of terrestrial feed ingredients and their suitability as replacements of fishmeal in diets for barramundi is reported in FRDC 93/120-04.

Final Report • 1999-10-20 • 9.41 MB
1992-063-DLD.pdf

Summary

Feed is by far the single largest cost component of barramundi farming and accounts for about 35% of on-farm operating costs. Reducing feed costs by better tailoring dietary specifications to the nutrient requirements of the fish, by providing these nutrients at least cost and by adopting feeding practices that optimise productivity will greatly assist farm profitability. In Australia, barramundi are pond-reared over latitudes from 5°S to 22°S and this results in large seasonal variations in water temperature and consequently, in growth rate of the fish.

The research conducted in this project sought primarily to characterise the effect of water temperature on fish productivity and how modification of dietary nutrient specifications and/or feeding practices could assist in improving farming profitability. This entailed research to define the fish's response to changes in dietary supply of critical nutrients over a range of water temperatures. Research examining the efficacy of crystalline amino acids in diets for barramundi was carried out in a supplementary project (FRDC 95/69); research on the nutritive value of terrestrial feed ingredients and their suitability as replacements of fishmeal in diets for barramundi is reported in FRDC 93/120-04.

Final Report • 1999-10-20 • 9.41 MB
1992-063-DLD.pdf

Summary

Feed is by far the single largest cost component of barramundi farming and accounts for about 35% of on-farm operating costs. Reducing feed costs by better tailoring dietary specifications to the nutrient requirements of the fish, by providing these nutrients at least cost and by adopting feeding practices that optimise productivity will greatly assist farm profitability. In Australia, barramundi are pond-reared over latitudes from 5°S to 22°S and this results in large seasonal variations in water temperature and consequently, in growth rate of the fish.

The research conducted in this project sought primarily to characterise the effect of water temperature on fish productivity and how modification of dietary nutrient specifications and/or feeding practices could assist in improving farming profitability. This entailed research to define the fish's response to changes in dietary supply of critical nutrients over a range of water temperatures. Research examining the efficacy of crystalline amino acids in diets for barramundi was carried out in a supplementary project (FRDC 95/69); research on the nutritive value of terrestrial feed ingredients and their suitability as replacements of fishmeal in diets for barramundi is reported in FRDC 93/120-04.

Second Australian National Prawn Seminar

Project number: 1983-067
Project Status:
Completed
Budget expenditure: $0.00
Organisation: CSIRO Oceans and Atmosphere Cleveland
Project start/end date: 28 Dec 1985 - 31 Dec 1985
Contact:
FRDC
TAGS
Tagging
Stock Assessment
Reproduction
Migration
Marketing

Objectives

1. Publish and distribute the proceedings of the Second Australian National Prawn Seminar

Proceedings

ISBN: 0 9589426 0 9
Authors: P.C. Rothlisberg B.J. Hill and D.J. Staples
Proceedings • 1985-12-31 • 15.86 MB
1983-067 Proceedings.pdf

Summary

Since the First Australian National Prawn Seminar in 1973, Australian prawn fisheries have grown in size and value to become Australia's most valuable fisheries resource. In the same period the number of people involved in the fishing industry, research and management has also increased. Major new research centres have been established and several new programs implemented. A wide array of management regimes have been introduced including limited entry, seasonal and area closures coupled with sampling regimes to optimise the size at which prawns are harvested. Recently there has been a resurgence of interest in penaeid aquaculture which has been stimulated by the marked increase in pond production in South America and South East Asia, and the impact the product is having on world markets.

Because of the wide geographic separation of the various Australian prawn fisheries, there is little opportunity for those involved in the industry to meet and discuss topics at the national level. Accordingly it was felt that an update of developments and progress in research, management, economics, marketing, and aquaculture was necessary. We formed an organising committee and obtained funds to cover conference and publication expenses.

The Second Australian National Prawn Seminar was held at Kooralbyn, Queensland from 22 to 26 October 1984.

Project products

Proceedings • 1985-12-31 • 15.86 MB
1983-067 Proceedings.pdf

Summary

Since the First Australian National Prawn Seminar in 1973, Australian prawn fisheries have grown in size and value to become Australia's most valuable fisheries resource. In the same period the number of people involved in the fishing industry, research and management has also increased. Major new research centres have been established and several new programs implemented. A wide array of management regimes have been introduced including limited entry, seasonal and area closures coupled with sampling regimes to optimise the size at which prawns are harvested. Recently there has been a resurgence of interest in penaeid aquaculture which has been stimulated by the marked increase in pond production in South America and South East Asia, and the impact the product is having on world markets.

Because of the wide geographic separation of the various Australian prawn fisheries, there is little opportunity for those involved in the industry to meet and discuss topics at the national level. Accordingly it was felt that an update of developments and progress in research, management, economics, marketing, and aquaculture was necessary. We formed an organising committee and obtained funds to cover conference and publication expenses.

The Second Australian National Prawn Seminar was held at Kooralbyn, Queensland from 22 to 26 October 1984.

Proceedings • 1985-12-31 • 15.86 MB
1983-067 Proceedings.pdf

Summary

Since the First Australian National Prawn Seminar in 1973, Australian prawn fisheries have grown in size and value to become Australia's most valuable fisheries resource. In the same period the number of people involved in the fishing industry, research and management has also increased. Major new research centres have been established and several new programs implemented. A wide array of management regimes have been introduced including limited entry, seasonal and area closures coupled with sampling regimes to optimise the size at which prawns are harvested. Recently there has been a resurgence of interest in penaeid aquaculture which has been stimulated by the marked increase in pond production in South America and South East Asia, and the impact the product is having on world markets.

Because of the wide geographic separation of the various Australian prawn fisheries, there is little opportunity for those involved in the industry to meet and discuss topics at the national level. Accordingly it was felt that an update of developments and progress in research, management, economics, marketing, and aquaculture was necessary. We formed an organising committee and obtained funds to cover conference and publication expenses.

The Second Australian National Prawn Seminar was held at Kooralbyn, Queensland from 22 to 26 October 1984.

Proceedings • 1985-12-31 • 15.86 MB
1983-067 Proceedings.pdf

Summary

Since the First Australian National Prawn Seminar in 1973, Australian prawn fisheries have grown in size and value to become Australia's most valuable fisheries resource. In the same period the number of people involved in the fishing industry, research and management has also increased. Major new research centres have been established and several new programs implemented. A wide array of management regimes have been introduced including limited entry, seasonal and area closures coupled with sampling regimes to optimise the size at which prawns are harvested. Recently there has been a resurgence of interest in penaeid aquaculture which has been stimulated by the marked increase in pond production in South America and South East Asia, and the impact the product is having on world markets.

Because of the wide geographic separation of the various Australian prawn fisheries, there is little opportunity for those involved in the industry to meet and discuss topics at the national level. Accordingly it was felt that an update of developments and progress in research, management, economics, marketing, and aquaculture was necessary. We formed an organising committee and obtained funds to cover conference and publication expenses.

The Second Australian National Prawn Seminar was held at Kooralbyn, Queensland from 22 to 26 October 1984.

Proceedings • 1985-12-31 • 15.86 MB
1983-067 Proceedings.pdf

Summary

Since the First Australian National Prawn Seminar in 1973, Australian prawn fisheries have grown in size and value to become Australia's most valuable fisheries resource. In the same period the number of people involved in the fishing industry, research and management has also increased. Major new research centres have been established and several new programs implemented. A wide array of management regimes have been introduced including limited entry, seasonal and area closures coupled with sampling regimes to optimise the size at which prawns are harvested. Recently there has been a resurgence of interest in penaeid aquaculture which has been stimulated by the marked increase in pond production in South America and South East Asia, and the impact the product is having on world markets.

Because of the wide geographic separation of the various Australian prawn fisheries, there is little opportunity for those involved in the industry to meet and discuss topics at the national level. Accordingly it was felt that an update of developments and progress in research, management, economics, marketing, and aquaculture was necessary. We formed an organising committee and obtained funds to cover conference and publication expenses.

The Second Australian National Prawn Seminar was held at Kooralbyn, Queensland from 22 to 26 October 1984.

Aquatic Animal Health Subprogram: Enhancing the emergency disease response capability of WA Department of Fisheries and industry bodies associated with freshwater crayfish culture

Project number: 2003-671
Project Status:
Completed
Budget expenditure: $22,161.00
Principal Investigator: Fran Stephens
Organisation: Department of Primary Industries and Regional Development (DPIRD) WA
Project start/end date: 30 Aug 2003 - 30 Jun 2005
Contact:
FRDC
TAGS
White Spot Disease
Training
Freshwater
Fisheries Management
Disease
SPECIES
Marron

Need

Relatively few major disease events have occurred within the WA aquaculture industries and as a result there has not been an opportunity for an integrated multi-agency approach, though one has been developed on
paper. To date, emergencies have been dealt with on an add-hoc basis and no large-scale containment or eradication programs have been undertaken with respect to aquatic animal diseases. The Department has also been fortunate that the remote and isolated nature of most of WA has not seriously affected the limited emergencies so far experienced, though considerable difficulties were experienced in collecting samples during the 2001 White Spot scare. It follows that relatively little experience in handling such emergencies currently
exists within the Department of Fisheries, WA. Simulation exercises provide a practical method of exposing and training staff in the management of aquatic disease emergencies.The need can be summarized as follows:
1. Both government and industries have limited experience with real emergencies.
2. Though there is a cohesive management strategy setting out the roles and responsibilities of individuals and agencies involved, it is untested.
3. The limited number of emergencies has lead to industry and agency complacency about the risks of disease introduction and the potential effects.
4. The linkages between all stakeholders on a national disease aquaculture event have not been tested. This exercise will test a national response as well as a local response. The freshwater crayfish industry in Western Australia is very keen to conduct the exercise and integrate the
products from N Buller and F Stephens.

Objectives

1. To examine and test the skills and abilities of the participants in-group problem solving and decision making skills relating to emergency response procedures.
2. To increase participant’s knowledge of communication routes to be used in an emergency disease response by working through a scenario which mimics a real emergency situation.To increase participant’s knowledge of communication routes to be used in an emergency disease response by working through a scenario which mimics a real emergency situation.
3. To clearly define the roles within and between the various agencies involved and how they fit within the WA Emergency plan and AQUAPLAN frameworks.
4. To improve participants ability to manage tasks by prioritizing a number of competing demands during the operational phase of an emergency response.
5. To increase participants understanding of the operational procedures in the Disease Emergency Response.
6. To familiarize participants with operational practices on freshwater crayfish farms of varying production technology (extensive and semi-intensive).
7. To identify key areas for improvement in emergency management procedures across a range of subjects including planning, communication, staffing and resourcing.
8. To document an emergency response plan that can be implemented by all stakeholders.
9. To familiarize all stakeholders including AFFA staff with the problems inherent in managing a disease in Cherax species that exist across Australia.

Final report

ISBN: 1-877098-59-0
Author: Frances Stephens
Final Report • 2004-09-23 • 2.54 MB
2003-671-DLD.pdf
Final Report • 2004-09-23 • 2.54 MB
2003-671-DLD.pdf
Final Report • 2004-09-23 • 2.54 MB
2003-671-DLD.pdf
Final Report • 2004-09-23 • 2.54 MB
2003-671-DLD.pdf
Final Report • 2004-09-23 • 2.54 MB
2003-671-DLD.pdf

Stock assessment of the outer-shelf species in the Kimberley region of tropical Western Australia

Project number: 1997-136
Project Status:
Completed
Budget expenditure: $343,428.00
Principal Investigator: Stephen J. Newman
Organisation: Department of Primary Industries and Regional Development (DPIRD) WA
Project start/end date: 22 Jun 1997 - 16 Jul 2003
Contact:
FRDC
TAGS
Sustainability
Stock Assessment
Population Dynamics
Mortality
Modelling

Need

The Kimberley Fishery is developing rapidly and is now a complex fishery producing a high quality product. The small amount of information available at present causes concern at the state of exploitation of the stocks. Information is required as soon as possible to enable effective management of the fishery. The tools available are controls on size at first capture and overall fishing mortality. It is more practical in the first instance to obtain the information which will enable control of size at first capture, and to follow this with the information needed to control fishing mortality.

The size selectivity of traps and lines needs to be examined to explore the possibility of using hook sizes and escape gaps in traps to reduce catches of smaller fish and hence increase long-term yields. Initial management controls can then be based on the outcome from size-at-first capture models. The size-at-first capture may be able to be controlled through the use of a mixture of fishing gear types (eg. fish traps in combination with lines and hooks of a specified size). The size-at-first capture of these fishes may also possibly be regulated through area controls, provided the distribution of adults and juveniles is known.

These preliminary management controls will need to be followed up with a broad area fish trawl survey to provide estimates of stock size for use in more complex stock assessment models, enabling subsequent management controls to be implemented with the aim of directly regulating fishing mortality. A trawl survey would add greatly to knowledge of distribution of adults and juveniles. Direct controls on fishing mortality by area can be applied by zoning of fishing effort, monitored through the use of Vessel Monitoring Systems. For logistic reasons the trawl survey is not included in the current proposal.

Specifically in this project there is a need to:

(i) determine the population parameters of goldband snapper, and other key demersal species to facilitate the development of fishery assessment models.

(ii) undertake a gear selectivity study (both traps and lines) to determine the feasibility of using gear controls such as hook size and escape gaps in traps.

There is a further critical need in future projects to obtain:
(1) direct stock size assessments via such methods as localised depletion experiments or broad area surveys;
(2) to obtain information about the interaction of the Australian and Indonesian fishery (assessment of catch and effort data) for these species;
(3) to obtain estimates of movement rates of the key species between regions and across borders (both national and international).

Objectives

1. Estimate essential population parameters of goldband snapper and other key demersal species.
2. Estimation, by yield-per-recruit and egg-per-recruit analyses, of optimum combinations for size-at-first capture and fishing mortality.
3. Comparison of the size selectivity of commercial trap and line gear and to investigate methods of altering selectivity to enable targeting of fish of a specific size.
4. Advise fishery managers and industry on the combinations of gear and effort controls to produce optimal sustainable yields.

Final report

ISBN: 0-7309-8460-5
Author: Stephen Newman
Final Report • 2003-03-14 • 2.22 MB
1997-136-DLD.pdf
Final Report • 2003-03-14 • 2.22 MB
1997-136-DLD.pdf
Final Report • 2003-03-14 • 2.22 MB
1997-136-DLD.pdf
Final Report • 2003-03-14 • 2.22 MB
1997-136-DLD.pdf
Final Report • 2003-03-14 • 2.22 MB
1997-136-DLD.pdf

Population dynamics and management of spanner crabs in southern Queensland

Project number: 1995-022
Project Status:
Completed
Budget expenditure: $262,552.00
Principal Investigator: Ian Brown
Organisation: Department of Primary Industries (QLD)
Project start/end date: 18 Dec 1995 - 30 Jun 2000
Contact:
FRDC
TAGS
Yield
Wild Catch
Sustainability
Population Dynamics
Mortality

Objectives

1. To estimate the size of the south Queensland spanner crab stock.
2. Determine the appropriateness of existing spawning closure arrangements.
3. To determine whether catch size-distribution can be used to estimate population age-structure and growth rates.
4. To evaluate the impact of post-discard mortality amongst sub-legal crabs on yields, and promote the development (by industry) of less damaging apparatus.

Final report

Authors: Ian Brown John Kirkwood Shane Gaddes Cathy Dichmont & Jenny Ovenden
Final Report • 1999-09-01 • 13.01 MB
1995-022-DLD.pdf

Summary

Spanner crabs (Ranina ranina) represent a valuable resource to southern Queensland and northern NSW. The fishery became established in the late 1970s, and as a result of an almost exponential increase in fishing effort between 1992 and 1995 an output-controlled limited entry management arrangement was introduced. During that period catches increased from about 800 to over 3,000 t, as the fishery expanded northwards to previously unexploited grounds, and a profitable live-export market was developed in south-east Asia.
The Queensland fleet comprises some 240 vessels specifically licenced to take spanner crabs in Managed Area A, which is subject to a Total Allowable Commercial Catch (TACC), currently set at 2600 t. Another 310 vessels are licenced to fish only in Managed Area B (north of the main fishing grounds) where the TACC does not apply. At present the TACC is competitive, but in the near future an Individual Transferrable Quota (ITQ) system is to be introduced.
Trends in commercial fisheries catch-effort statistics indicate that the spanner crab stock in southern Queensland is currently being harvested at a sustainable level. However several questions remain with respect to the application of the commercial logbook data, possibly the most important of which is how well commercial catch-per-unit-effoti represents stock abundance. The spatial distribution of spanner crabs is patchy, and the fishery operates such that patches are located, targeted and fished down. This can potentially lead to a situation of hyperstability, where the stock is actually declining despite catch rates remaining constant. This highlights the expected value of the fishery-independent monitoring programme currently being planned by QDPI with (in the case of the spanner crab fishery) a significant level of cost-recovery from industry.
Previous attempts to estimate growth rate of spanner crabs resulted in little consensus, due in part to inadequate sample sizes (length-based methods) and uncertainty surrounding the effects of tagging on growth (tag-recapture methods). Our initial objective was to determine whether the length-based methods would work if the samples were very large.
 
Variability in the size-structure of even very large samples of adult crabs was so great that we could place little confidence in growth estimates obtained from this type of data. Because of this, we negotiated a change in research direction with FRDC, focussing on two alternative approaches to the question of growth rates. The first was to investigate growth in pre-recruits. The second was to quantify the likely effect of tagging on moulting and growth, and to determine the extent of growth rate differences between NSW and Queensland.
Very small spanner crabs are not taken by baited tangle nets, regardless of mesh size, so a different sampling arrangement was required. A two-track channel dredge was successful in capturing intact megalopae and early juvenile stages, which provided length frequency data of considerable value to estimating pre-recruit growth. However because of its small size only very limited samples were able to be collected. To increase the sampling volume we developed a substantially larger, hydraulically­assisted dredge. This device has been field-tested on several occasions, but it has not yet been developed and used to full effect.
Laboratory experiments demonstrated that tagging had an adverse effect on weight increase and survival of spanner crabs, suggesting that growth rate estimates based on mark-recapture techniques may be biased. Of the several different types tested, anchor tags were superior in terms of ease of application and visibility. Recognising that the results may be biased, we released 4,804 tagged crabs at sites throughout the fishing grounds, to determine whether growth of spanner crabs in Queensland waters is significantly different from that in NSW, reported in a previous study. Fourteen of the 221 crabs recaptured in 1998 had moulted, with growth male growth increments being greater than those offemales (X = 11.86 and 7.40 mm respectively). Recapture rates were significantly higher for males than females, and were also significantly greater for larger individuals of each sex. This suggests that tag mortality was greater in the smaller size-classes. Recaptured crabs had moved distances ranging from O to 45 km since release, but showed no tendency to move in any particular direction.
Our length-based assessment model has not yet been successful in producing useful estimates of the relevant stock performance indicators for use by management. This was due to the lack of contrast in the CPUE data, the relatively short data time-series, the extreme spatial and temporal variability in population size-structure and sex-ratio as represented in commercial catches and research samples, and the absence of definitive growth data.
Mitochondrial DNA analysis indicated that the east-coast spanner crab fishery comprises a single unit stock, and there thus appears to be no biological justification for separate management arrangements in different geographic areas.
 
Analysis of reproductive chronology indicates that the timing of the existing spawning closure is appropriate for minimising mortality amongst egg-bearing female spanner crabs across the entire fishery, and we recommend that the closure be retained in legislation.
 
Exploratory surveys for spanner crabs conducted in two areas outside the current fishing grounds did not reveal any significant quantity of crabs, although small numbers were captured at two sites amongst the Swain Reefs. From the available information it seems unlikely that there are any major unexploited populations of spanner crabs remaining in Queensland waters.
We have demonstrated that limb damage to undersized discarded spanner crabs has a major effect on their survival under natural conditions. Poor handling practices in the fishery result in considerable mortality amongst discarded small crabs, highlighting the need for continuing fisher education and ongoing investigation of alternative catching apparatus.
 
The two major issues for further research into the spanner crab fishery are (i) deriving a robust estimate of the species' growth rate, (ii) investigating the source of the extreme variability in size­frequency and sex-ratios in population samples.
Final Report • 1999-09-01 • 13.01 MB
1995-022-DLD.pdf

Summary

Spanner crabs (Ranina ranina) represent a valuable resource to southern Queensland and northern NSW. The fishery became established in the late 1970s, and as a result of an almost exponential increase in fishing effort between 1992 and 1995 an output-controlled limited entry management arrangement was introduced. During that period catches increased from about 800 to over 3,000 t, as the fishery expanded northwards to previously unexploited grounds, and a profitable live-export market was developed in south-east Asia.
The Queensland fleet comprises some 240 vessels specifically licenced to take spanner crabs in Managed Area A, which is subject to a Total Allowable Commercial Catch (TACC), currently set at 2600 t. Another 310 vessels are licenced to fish only in Managed Area B (north of the main fishing grounds) where the TACC does not apply. At present the TACC is competitive, but in the near future an Individual Transferrable Quota (ITQ) system is to be introduced.
Trends in commercial fisheries catch-effort statistics indicate that the spanner crab stock in southern Queensland is currently being harvested at a sustainable level. However several questions remain with respect to the application of the commercial logbook data, possibly the most important of which is how well commercial catch-per-unit-effoti represents stock abundance. The spatial distribution of spanner crabs is patchy, and the fishery operates such that patches are located, targeted and fished down. This can potentially lead to a situation of hyperstability, where the stock is actually declining despite catch rates remaining constant. This highlights the expected value of the fishery-independent monitoring programme currently being planned by QDPI with (in the case of the spanner crab fishery) a significant level of cost-recovery from industry.
Previous attempts to estimate growth rate of spanner crabs resulted in little consensus, due in part to inadequate sample sizes (length-based methods) and uncertainty surrounding the effects of tagging on growth (tag-recapture methods). Our initial objective was to determine whether the length-based methods would work if the samples were very large.
 
Variability in the size-structure of even very large samples of adult crabs was so great that we could place little confidence in growth estimates obtained from this type of data. Because of this, we negotiated a change in research direction with FRDC, focussing on two alternative approaches to the question of growth rates. The first was to investigate growth in pre-recruits. The second was to quantify the likely effect of tagging on moulting and growth, and to determine the extent of growth rate differences between NSW and Queensland.
Very small spanner crabs are not taken by baited tangle nets, regardless of mesh size, so a different sampling arrangement was required. A two-track channel dredge was successful in capturing intact megalopae and early juvenile stages, which provided length frequency data of considerable value to estimating pre-recruit growth. However because of its small size only very limited samples were able to be collected. To increase the sampling volume we developed a substantially larger, hydraulically­assisted dredge. This device has been field-tested on several occasions, but it has not yet been developed and used to full effect.
Laboratory experiments demonstrated that tagging had an adverse effect on weight increase and survival of spanner crabs, suggesting that growth rate estimates based on mark-recapture techniques may be biased. Of the several different types tested, anchor tags were superior in terms of ease of application and visibility. Recognising that the results may be biased, we released 4,804 tagged crabs at sites throughout the fishing grounds, to determine whether growth of spanner crabs in Queensland waters is significantly different from that in NSW, reported in a previous study. Fourteen of the 221 crabs recaptured in 1998 had moulted, with growth male growth increments being greater than those offemales (X = 11.86 and 7.40 mm respectively). Recapture rates were significantly higher for males than females, and were also significantly greater for larger individuals of each sex. This suggests that tag mortality was greater in the smaller size-classes. Recaptured crabs had moved distances ranging from O to 45 km since release, but showed no tendency to move in any particular direction.
Our length-based assessment model has not yet been successful in producing useful estimates of the relevant stock performance indicators for use by management. This was due to the lack of contrast in the CPUE data, the relatively short data time-series, the extreme spatial and temporal variability in population size-structure and sex-ratio as represented in commercial catches and research samples, and the absence of definitive growth data.
Mitochondrial DNA analysis indicated that the east-coast spanner crab fishery comprises a single unit stock, and there thus appears to be no biological justification for separate management arrangements in different geographic areas.
 
Analysis of reproductive chronology indicates that the timing of the existing spawning closure is appropriate for minimising mortality amongst egg-bearing female spanner crabs across the entire fishery, and we recommend that the closure be retained in legislation.
 
Exploratory surveys for spanner crabs conducted in two areas outside the current fishing grounds did not reveal any significant quantity of crabs, although small numbers were captured at two sites amongst the Swain Reefs. From the available information it seems unlikely that there are any major unexploited populations of spanner crabs remaining in Queensland waters.
We have demonstrated that limb damage to undersized discarded spanner crabs has a major effect on their survival under natural conditions. Poor handling practices in the fishery result in considerable mortality amongst discarded small crabs, highlighting the need for continuing fisher education and ongoing investigation of alternative catching apparatus.
 
The two major issues for further research into the spanner crab fishery are (i) deriving a robust estimate of the species' growth rate, (ii) investigating the source of the extreme variability in size­frequency and sex-ratios in population samples.
Final Report • 1999-09-01 • 13.01 MB
1995-022-DLD.pdf

Summary

Spanner crabs (Ranina ranina) represent a valuable resource to southern Queensland and northern NSW. The fishery became established in the late 1970s, and as a result of an almost exponential increase in fishing effort between 1992 and 1995 an output-controlled limited entry management arrangement was introduced. During that period catches increased from about 800 to over 3,000 t, as the fishery expanded northwards to previously unexploited grounds, and a profitable live-export market was developed in south-east Asia.
The Queensland fleet comprises some 240 vessels specifically licenced to take spanner crabs in Managed Area A, which is subject to a Total Allowable Commercial Catch (TACC), currently set at 2600 t. Another 310 vessels are licenced to fish only in Managed Area B (north of the main fishing grounds) where the TACC does not apply. At present the TACC is competitive, but in the near future an Individual Transferrable Quota (ITQ) system is to be introduced.
Trends in commercial fisheries catch-effort statistics indicate that the spanner crab stock in southern Queensland is currently being harvested at a sustainable level. However several questions remain with respect to the application of the commercial logbook data, possibly the most important of which is how well commercial catch-per-unit-effoti represents stock abundance. The spatial distribution of spanner crabs is patchy, and the fishery operates such that patches are located, targeted and fished down. This can potentially lead to a situation of hyperstability, where the stock is actually declining despite catch rates remaining constant. This highlights the expected value of the fishery-independent monitoring programme currently being planned by QDPI with (in the case of the spanner crab fishery) a significant level of cost-recovery from industry.
Previous attempts to estimate growth rate of spanner crabs resulted in little consensus, due in part to inadequate sample sizes (length-based methods) and uncertainty surrounding the effects of tagging on growth (tag-recapture methods). Our initial objective was to determine whether the length-based methods would work if the samples were very large.
 
Variability in the size-structure of even very large samples of adult crabs was so great that we could place little confidence in growth estimates obtained from this type of data. Because of this, we negotiated a change in research direction with FRDC, focussing on two alternative approaches to the question of growth rates. The first was to investigate growth in pre-recruits. The second was to quantify the likely effect of tagging on moulting and growth, and to determine the extent of growth rate differences between NSW and Queensland.
Very small spanner crabs are not taken by baited tangle nets, regardless of mesh size, so a different sampling arrangement was required. A two-track channel dredge was successful in capturing intact megalopae and early juvenile stages, which provided length frequency data of considerable value to estimating pre-recruit growth. However because of its small size only very limited samples were able to be collected. To increase the sampling volume we developed a substantially larger, hydraulically­assisted dredge. This device has been field-tested on several occasions, but it has not yet been developed and used to full effect.
Laboratory experiments demonstrated that tagging had an adverse effect on weight increase and survival of spanner crabs, suggesting that growth rate estimates based on mark-recapture techniques may be biased. Of the several different types tested, anchor tags were superior in terms of ease of application and visibility. Recognising that the results may be biased, we released 4,804 tagged crabs at sites throughout the fishing grounds, to determine whether growth of spanner crabs in Queensland waters is significantly different from that in NSW, reported in a previous study. Fourteen of the 221 crabs recaptured in 1998 had moulted, with growth male growth increments being greater than those offemales (X = 11.86 and 7.40 mm respectively). Recapture rates were significantly higher for males than females, and were also significantly greater for larger individuals of each sex. This suggests that tag mortality was greater in the smaller size-classes. Recaptured crabs had moved distances ranging from O to 45 km since release, but showed no tendency to move in any particular direction.
Our length-based assessment model has not yet been successful in producing useful estimates of the relevant stock performance indicators for use by management. This was due to the lack of contrast in the CPUE data, the relatively short data time-series, the extreme spatial and temporal variability in population size-structure and sex-ratio as represented in commercial catches and research samples, and the absence of definitive growth data.
Mitochondrial DNA analysis indicated that the east-coast spanner crab fishery comprises a single unit stock, and there thus appears to be no biological justification for separate management arrangements in different geographic areas.
 
Analysis of reproductive chronology indicates that the timing of the existing spawning closure is appropriate for minimising mortality amongst egg-bearing female spanner crabs across the entire fishery, and we recommend that the closure be retained in legislation.
 
Exploratory surveys for spanner crabs conducted in two areas outside the current fishing grounds did not reveal any significant quantity of crabs, although small numbers were captured at two sites amongst the Swain Reefs. From the available information it seems unlikely that there are any major unexploited populations of spanner crabs remaining in Queensland waters.
We have demonstrated that limb damage to undersized discarded spanner crabs has a major effect on their survival under natural conditions. Poor handling practices in the fishery result in considerable mortality amongst discarded small crabs, highlighting the need for continuing fisher education and ongoing investigation of alternative catching apparatus.
 
The two major issues for further research into the spanner crab fishery are (i) deriving a robust estimate of the species' growth rate, (ii) investigating the source of the extreme variability in size­frequency and sex-ratios in population samples.
Final Report • 1999-09-01 • 13.01 MB
1995-022-DLD.pdf

Summary

Spanner crabs (Ranina ranina) represent a valuable resource to southern Queensland and northern NSW. The fishery became established in the late 1970s, and as a result of an almost exponential increase in fishing effort between 1992 and 1995 an output-controlled limited entry management arrangement was introduced. During that period catches increased from about 800 to over 3,000 t, as the fishery expanded northwards to previously unexploited grounds, and a profitable live-export market was developed in south-east Asia.
The Queensland fleet comprises some 240 vessels specifically licenced to take spanner crabs in Managed Area A, which is subject to a Total Allowable Commercial Catch (TACC), currently set at 2600 t. Another 310 vessels are licenced to fish only in Managed Area B (north of the main fishing grounds) where the TACC does not apply. At present the TACC is competitive, but in the near future an Individual Transferrable Quota (ITQ) system is to be introduced.
Trends in commercial fisheries catch-effort statistics indicate that the spanner crab stock in southern Queensland is currently being harvested at a sustainable level. However several questions remain with respect to the application of the commercial logbook data, possibly the most important of which is how well commercial catch-per-unit-effoti represents stock abundance. The spatial distribution of spanner crabs is patchy, and the fishery operates such that patches are located, targeted and fished down. This can potentially lead to a situation of hyperstability, where the stock is actually declining despite catch rates remaining constant. This highlights the expected value of the fishery-independent monitoring programme currently being planned by QDPI with (in the case of the spanner crab fishery) a significant level of cost-recovery from industry.
Previous attempts to estimate growth rate of spanner crabs resulted in little consensus, due in part to inadequate sample sizes (length-based methods) and uncertainty surrounding the effects of tagging on growth (tag-recapture methods). Our initial objective was to determine whether the length-based methods would work if the samples were very large.
 
Variability in the size-structure of even very large samples of adult crabs was so great that we could place little confidence in growth estimates obtained from this type of data. Because of this, we negotiated a change in research direction with FRDC, focussing on two alternative approaches to the question of growth rates. The first was to investigate growth in pre-recruits. The second was to quantify the likely effect of tagging on moulting and growth, and to determine the extent of growth rate differences between NSW and Queensland.
Very small spanner crabs are not taken by baited tangle nets, regardless of mesh size, so a different sampling arrangement was required. A two-track channel dredge was successful in capturing intact megalopae and early juvenile stages, which provided length frequency data of considerable value to estimating pre-recruit growth. However because of its small size only very limited samples were able to be collected. To increase the sampling volume we developed a substantially larger, hydraulically­assisted dredge. This device has been field-tested on several occasions, but it has not yet been developed and used to full effect.
Laboratory experiments demonstrated that tagging had an adverse effect on weight increase and survival of spanner crabs, suggesting that growth rate estimates based on mark-recapture techniques may be biased. Of the several different types tested, anchor tags were superior in terms of ease of application and visibility. Recognising that the results may be biased, we released 4,804 tagged crabs at sites throughout the fishing grounds, to determine whether growth of spanner crabs in Queensland waters is significantly different from that in NSW, reported in a previous study. Fourteen of the 221 crabs recaptured in 1998 had moulted, with growth male growth increments being greater than those offemales (X = 11.86 and 7.40 mm respectively). Recapture rates were significantly higher for males than females, and were also significantly greater for larger individuals of each sex. This suggests that tag mortality was greater in the smaller size-classes. Recaptured crabs had moved distances ranging from O to 45 km since release, but showed no tendency to move in any particular direction.
Our length-based assessment model has not yet been successful in producing useful estimates of the relevant stock performance indicators for use by management. This was due to the lack of contrast in the CPUE data, the relatively short data time-series, the extreme spatial and temporal variability in population size-structure and sex-ratio as represented in commercial catches and research samples, and the absence of definitive growth data.
Mitochondrial DNA analysis indicated that the east-coast spanner crab fishery comprises a single unit stock, and there thus appears to be no biological justification for separate management arrangements in different geographic areas.
 
Analysis of reproductive chronology indicates that the timing of the existing spawning closure is appropriate for minimising mortality amongst egg-bearing female spanner crabs across the entire fishery, and we recommend that the closure be retained in legislation.
 
Exploratory surveys for spanner crabs conducted in two areas outside the current fishing grounds did not reveal any significant quantity of crabs, although small numbers were captured at two sites amongst the Swain Reefs. From the available information it seems unlikely that there are any major unexploited populations of spanner crabs remaining in Queensland waters.
We have demonstrated that limb damage to undersized discarded spanner crabs has a major effect on their survival under natural conditions. Poor handling practices in the fishery result in considerable mortality amongst discarded small crabs, highlighting the need for continuing fisher education and ongoing investigation of alternative catching apparatus.
 
The two major issues for further research into the spanner crab fishery are (i) deriving a robust estimate of the species' growth rate, (ii) investigating the source of the extreme variability in size­frequency and sex-ratios in population samples.
Final Report • 1999-09-01 • 13.01 MB
1995-022-DLD.pdf

Summary

Spanner crabs (Ranina ranina) represent a valuable resource to southern Queensland and northern NSW. The fishery became established in the late 1970s, and as a result of an almost exponential increase in fishing effort between 1992 and 1995 an output-controlled limited entry management arrangement was introduced. During that period catches increased from about 800 to over 3,000 t, as the fishery expanded northwards to previously unexploited grounds, and a profitable live-export market was developed in south-east Asia.
The Queensland fleet comprises some 240 vessels specifically licenced to take spanner crabs in Managed Area A, which is subject to a Total Allowable Commercial Catch (TACC), currently set at 2600 t. Another 310 vessels are licenced to fish only in Managed Area B (north of the main fishing grounds) where the TACC does not apply. At present the TACC is competitive, but in the near future an Individual Transferrable Quota (ITQ) system is to be introduced.
Trends in commercial fisheries catch-effort statistics indicate that the spanner crab stock in southern Queensland is currently being harvested at a sustainable level. However several questions remain with respect to the application of the commercial logbook data, possibly the most important of which is how well commercial catch-per-unit-effoti represents stock abundance. The spatial distribution of spanner crabs is patchy, and the fishery operates such that patches are located, targeted and fished down. This can potentially lead to a situation of hyperstability, where the stock is actually declining despite catch rates remaining constant. This highlights the expected value of the fishery-independent monitoring programme currently being planned by QDPI with (in the case of the spanner crab fishery) a significant level of cost-recovery from industry.
Previous attempts to estimate growth rate of spanner crabs resulted in little consensus, due in part to inadequate sample sizes (length-based methods) and uncertainty surrounding the effects of tagging on growth (tag-recapture methods). Our initial objective was to determine whether the length-based methods would work if the samples were very large.
 
Variability in the size-structure of even very large samples of adult crabs was so great that we could place little confidence in growth estimates obtained from this type of data. Because of this, we negotiated a change in research direction with FRDC, focussing on two alternative approaches to the question of growth rates. The first was to investigate growth in pre-recruits. The second was to quantify the likely effect of tagging on moulting and growth, and to determine the extent of growth rate differences between NSW and Queensland.
Very small spanner crabs are not taken by baited tangle nets, regardless of mesh size, so a different sampling arrangement was required. A two-track channel dredge was successful in capturing intact megalopae and early juvenile stages, which provided length frequency data of considerable value to estimating pre-recruit growth. However because of its small size only very limited samples were able to be collected. To increase the sampling volume we developed a substantially larger, hydraulically­assisted dredge. This device has been field-tested on several occasions, but it has not yet been developed and used to full effect.
Laboratory experiments demonstrated that tagging had an adverse effect on weight increase and survival of spanner crabs, suggesting that growth rate estimates based on mark-recapture techniques may be biased. Of the several different types tested, anchor tags were superior in terms of ease of application and visibility. Recognising that the results may be biased, we released 4,804 tagged crabs at sites throughout the fishing grounds, to determine whether growth of spanner crabs in Queensland waters is significantly different from that in NSW, reported in a previous study. Fourteen of the 221 crabs recaptured in 1998 had moulted, with growth male growth increments being greater than those offemales (X = 11.86 and 7.40 mm respectively). Recapture rates were significantly higher for males than females, and were also significantly greater for larger individuals of each sex. This suggests that tag mortality was greater in the smaller size-classes. Recaptured crabs had moved distances ranging from O to 45 km since release, but showed no tendency to move in any particular direction.
Our length-based assessment model has not yet been successful in producing useful estimates of the relevant stock performance indicators for use by management. This was due to the lack of contrast in the CPUE data, the relatively short data time-series, the extreme spatial and temporal variability in population size-structure and sex-ratio as represented in commercial catches and research samples, and the absence of definitive growth data.
Mitochondrial DNA analysis indicated that the east-coast spanner crab fishery comprises a single unit stock, and there thus appears to be no biological justification for separate management arrangements in different geographic areas.
 
Analysis of reproductive chronology indicates that the timing of the existing spawning closure is appropriate for minimising mortality amongst egg-bearing female spanner crabs across the entire fishery, and we recommend that the closure be retained in legislation.
 
Exploratory surveys for spanner crabs conducted in two areas outside the current fishing grounds did not reveal any significant quantity of crabs, although small numbers were captured at two sites amongst the Swain Reefs. From the available information it seems unlikely that there are any major unexploited populations of spanner crabs remaining in Queensland waters.
We have demonstrated that limb damage to undersized discarded spanner crabs has a major effect on their survival under natural conditions. Poor handling practices in the fishery result in considerable mortality amongst discarded small crabs, highlighting the need for continuing fisher education and ongoing investigation of alternative catching apparatus.
 
The two major issues for further research into the spanner crab fishery are (i) deriving a robust estimate of the species' growth rate, (ii) investigating the source of the extreme variability in size­frequency and sex-ratios in population samples.
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