2 results

Determining appropriate sizes at harvest for species shared by the commercial trap and recreational fisheries in New South Wales

Project number: 2004-035
Project Status:
Completed
Budget expenditure: $310,933.00
Principal Investigator: John Stewart
Organisation: Department of Primary Industries and Regional Development (NSW)
Project start/end date: 16 Feb 2005 - 28 Feb 2008
Contact:
FRDC
TAGS
Recreational Fishing
Harvest Strategy
Fishing Gear
Fishing Effort
Fisheries Management
SPECIES
Ocean Jacket
Grey Morwong
Mulloway
Tarwhine
Yellowfin Bream

Need

Available evidence suggests that most fish species harvested by the NSW demersal trap and recreational fisheries are taken at sizes that are too small to optimise yield and/or economic return. This is because most species taken in both of these fisheries either have MLL’s that are too small or do not have MLL's at all. There have only been stock assessments done on snapper (FRDC project No. 93/074) and silver trevally (FRDC project No. 97/125) in the trap fishery. Both studies showed that they were growth overfished and the results have been used to increase the MLL for snapper and to impose a MLL for silver trevally across all fisheries. Many other species taken by fish traps are in decline and it is highly likely that they are also growth overfished. Unfortunately, very little is known about the biology or life-history of these other species. Recreational fishers are significant harvesters of all species taken in the NSW demersal trap fishery and it is important that any MLL’s designed to reduce overfishing are applied across all fisheries.

NSW Fisheries does not currently have a policy for setting MLL's at particular sizes and the process developed during this study may form the basis for such a policy. It is important to consider several issues when setting appropriate harvest sizes and these include: (i) the size at sexual maturity; (ii) the size that will optimise yield; (iii) market requirements; (iv) an economic assessment, and (iv) public perception.

The information on biology, stock-assessment and protocols for setting appropriate harvest sizes developed during this project will directly address several key areas of importance recognized by the FRDC. The planned outcomes will lead to fisheries management being based more on the precautionary principle, will maximise the economic and social returns from harvesting these species while also providing for effective management of recreational fishing. These areas are considered to be high priorities by the NSW FRAB and by Recfish Australia in their National Research and Development plan for the recreational sector.

Objectives

1. To develop a framework based on biological, economic and social information by which appropriate harvest sizes can be determined.
2. To recommend appropriate sizes at harvest for primary species shared by the commercial trap and recreational fisheries in NSW.
3. Where appropriate to recommend minimum legal lengths for species across all fisheries.

Final report

Author: John Stewart
Final Report • 2008-11-24
2004-035-DLD.pdf

Mesh selectivity in the NSW demersal trap fishery

Project number: 1998-138
Project Status:
Completed
Budget expenditure: $188,040.05
Principal Investigator: Doug Ferrell
Organisation: Department of Primary Industries and Regional Development (NSW)
Project start/end date: 28 Jun 1998 - 12 Jun 2002
Contact:
FRDC
TAGS
Fishing Gear
Fisheries Management
Bycatch
SPECIES
Ocean Jacket
Blue Morwong
Yellowfin Bream
Snapper
Silver Trevally

Need

Reduction of by-catch has been an active area for research in Australia and around the world. The initial focus for research and management has been demersal trawl fishing, where the perception of waste and potential impact has been the greatest. However, the reasons for seeking to reduce unwanted catch apply to all fisheries, including those using demersal traps.

Demersal fish traps in NSW must be covered with mesh no smaller than 50 mm, and a galvanised hexagonal fencing wire is the most common material. However, many fishers use larger mesh and both 50 X 75 mm and 75 mm hexagonal mesh are in use. Those using and advocating larger mesh have done so to reduce the catch of undersize snapper and other small fish and to decrease sorting times. Other trappers are concerned about the effect of larger mesh dimensions on the catch of valuable species such as wrasses, sweep or bream which all have no minimum legal length (MLL) or have an MLL smaller than snapper.

An understanding of the differences in selectivity of different sizes of mesh on the species caught in fish traps will have a number of uses. This information is essential to determine the cost and benefit to fishers of changing mesh sizes. The selection probabilities for existing meshes can also be used to improve the assessments using age and length composition collected for snapper and bream in NSW. This is particularly important for snapper, where a very large proportion of the fishery is caught close to the MLL. Finally, because wire mesh can be made in a diversity of shapes and sizes, it may be possible to achieve desirable changes in selectivity for some species while not changing selectivity patterns for others.

Objectives

1. Document throughout NSW, the current usage patterns of the various mesh types used in demersal fish traps.
2. Describe the size composition of retained and returned catch for species common in the NSW trap fishery for all mesh types as they are currently used.
3. Describe size composition of retained and returned catch for commercially available mesh and wire products in areas where they are not currently fished.
4. Determine the likely utility of possible mesh configurations not currently in use.

Final report

Author: Doug Ferrell
Final Report • 2002-04-30 • 1.76 MB
1998-138-DLD.pdf

Summary

The New South Wales demersal trap fishery is a complex, multi-species fishery.  The most valuable species in the fishery is snapper, worth approximately half the value of the fishery, with bream, rubberlip morwong, ocean leatherjacket, silver trevally, sweep and pigfish accounting for a further 36% of the fishery.  Current regulations specify that traps must be covered with mesh having a measurement from one plain wire to the opposite plain wire of not less than 50 mm, and a 50 mm hexagonal fencing wire is the most commonly used trap mesh.  We know that 50 mm hexagonal wire mesh retains undersized snapper and some fishers advocate using panels of 50 x 75 mm welded mesh in their traps to reduce the catch of small, unwanted fish.  We needed knowledge concerning discarding of fish in the trap fishery, because it was apparent that the mesh selectivity of the currently used 50 mm hexagonal wire is inappropriate for snapper, and probably also for many other species captured in traps.
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