Maximizing the survival of bycatch released from commercial estuarine fishing gears in NSW
In NSW, inherent variation among the characteristics of different estuarine fisheries has resulted in a range of physical modifications designed to improve the selectivity of conventional gears. While some of these designs have been effective in reducing the bycatches of unwanted species by up to 95%, rates of reduction more commonly range between 30 and 70%. Such reductions have obvious benefits for the stocks of bycatch species. considering the magnitudes of bycatches in many estuarine fisheries, and especially those targeting prawns (i.e. often 1000s of fish per haul), it is apparent that despite the use of modified gears, in nearly all cases there still remains some capture and mortality of unwanted individuals.
To augment the post-release survival of unwanted bycatch throughout nearly all of NSW estuarine fisheries (including those involving static gears, where no BRDs have been developed), ancillary options within the second category of input controls (listed above in B2) need to be investigated. The sorts of modifications that warrant examination include, defined soak times for gears, devices to limit predation on discarded bycatch, netting materials in codends that reduce damage to bycatch, the use of gloves to handle bycatch, and the utility of separating target and bycaught species in water after capture.
The majority of these operational and/or post-capture handling procedures have NOT been examined, but have the potential to significantly reduce the remaining impacts of commercial fishing gears on non-target species and sizes in NSW’s estuaries. This is one of the main research priorities detailed in the Fishery Management Strategy for the NSW Estuary General Fishery and comprises a key category within the 2004-2007 Strategic Research Plan for Fisheries, Aquaculture and Aquatic Conservation in NSW. Quantification of the utility of this category of input controls would also have benefit and application throughout all other coastal fisheries in Australia.
The research will form the basis of a PhD candidature. This approach is justified because (i) the work is new and there is sufficient intellectual content to support a PhD student, (ii) there is a paucity of researchers with higher degrees working in the applied fields of gear technology and bycatch mitigation in Australia and (iii) previous, similarly-structured FRDC projects (e.g. 93/180 and 2001/031) have resulted in successful PhD candidatures by project staff. Specifying a PhD candidature formalizes what would already occur if funding was sought for a Fisheries Technician, but at approx. 1/3 the cost, while attracting a substantial in-kind contribution from affiliated institutions (the National Marine Science Centre and University of New England).
Final report
Determining appropriate sizes at harvest for species shared by the commercial trap and recreational fisheries in New South Wales
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.