Non Technical Summary

Commercial prawn fisheries in NSW involve the use of various different types of small-meshed nets, which are not very selective fishing gears. In addition to the targeted prawns, many of these nets retain large quantities of unwanted organisms, termed bycatch. In many fisheries, this bycatch consists of large numbers of small fish and crustaceans, including prawns that are smaller than the optimal commercial size.

The bycatch of unwanted fish has been addressed in some prawn fisheries, via the use of physical modifications to gears (termed Bycatch Reduction Devices), however, less attention has been paid to the discarding and mortality of small unwanted prawns. In fact, until now, there has been no research done to examine the current selectivity of school and king prawns in any of the gears used to catch them in NSW. It is known, however, that most fishing methods catch large numbers of very small school and king prawns that are discarded well after capture. If excluded from nets underwater, these small prawns should, in a relatively short period of time, provide substantially improved catches of the more desirable and valuable sizes of prawns.

This output are letters to commercial fishers summarising preliminary results from recent experiments in the Clarence and Richmond Rivers to determine the selectivity of conventional diamond- and new square-mesh codends in pocket and haul nets. Like the results from similar work done in the Clarence River trawl fishery, we showed that the existing diamond-mesh codends have poor selectivity characteristics and that increasing mesh openings via the use of square-mesh can significantly improve selectivity, while reducing unwanted bycatch. Further research is being done to assess the full potential of these new codend designs.