Prawn resources underpin some of the most economically important fisheries in Australia and form the basis of very important recreational fisheries. Ecologically sustainable development of fisheries resources partly depends on catching species at optimal sizes and there is considerable concern that the gears being used in NSW’s commercial and recreational prawn fisheries catch them at sizes smaller than that which optimises biological yield.
Prawn fisheries in NSW (and the world) have attracted enormous attention in the past few decades over their by-catch of non-targeted species – especially juvenile fish. In NSW, this led to the development, implementation and legislation of various gear-based solutions like the Nordmore Grid and square mesh panels (see attached publication list). A major by-catch issue remaining for NSW’s prawn fisheries concerns the by-catch and discard of unsaleable sizes of school and king prawns. Currently, large numbers of small prawns are discarded well after capture (sometimes even after cooking) through the process of “riddling” which involves passing the prawn catch over a sieve to separate large and small individuals. This is considered a major waste of a resource – especially since it is known that, for fast-growing prawns, undersize individuals could be expected to reach a desirable size in a relatively short time. Unfortunately, virtually no research has been done on the selectivity of school and king prawns in any of the gears used to catch them (i.e. prawn trawls, haul nets, set pocket nets and snigging nets in commercial fisheries; and dragnets and scoop nets in recreational fisheries). All are thought to catch large numbers of very small school and king prawns that are discarded well after capture. If excluded from nets underwater, these prawns should, in a relatively short period of time, provide substantially improved catches of the more desirable and valuable sizes of prawns.
In 1998, Broadhurst, Larsen, Kennelly and McShane developed a codend made entirely of small square mesh to reduce the discards of small western king prawns in Gulf St Vincent, South Australia. The current application is for funds to develop full square-meshed codends and other methods to decrease the discard of small prawns throughout the many commercial and recreational prawn fisheries of NSW.
