Differences in Catch Composition among Types of Commercial Penaeid-Seining Operations in an Australian Estuary

Three variants of commercial penaeid prawn (or shrimp) seining are done in the Wallis Lake estuarine system in New South Wales (NSW), Australia (day-time river, and day- and night-time lagoon), which are operated differently according to the type of habitat and time of day in which they are used. A large-scale observer study was done during the 1998-1999 and 2001-2002 prawn seining seasons to quantify penaeid-seine catches in this estuary. These data were used to compare the species composition of penaeid catches and non-penaeid bycatches across the three types of seining. Catch compositions varied considerably – mostly according to the specific habitat being fished (i.e. riverine vs. coastal lagoon) and time of day. Currently, the codends of all NSW seines are restricted to a legal stretched-mesh opening of between 30 and 36 mm and are constructed of diamond-shaped mesh throughout. Recent research with some NSW penaeid seines (including Wallis Lake night-time lagoon seines) has, however, demonstrated the utility of codends made from square-shaped mesh (i.e. hung on the bar) for reducing the bycatch of unwanted small fauna. Consequently, the compulsory use of square-mesh codends in most penaeid seines throughout NSW is being considered as a management strategy for reducing bycatch. We discuss the differences in catches among the three seining variants in terms of the implementation of square-mesh codends, and recommend that appropriate rigorous trials with such codends be conducted for each seining variant in each NSW estuary prior to mandating their use.