Optimising the collection of relative abundance data for the pipi population in New South Wales
Long-term information on the abundance and size structure of pipi stocks in NSW is needed to support new management arrangements for the pipi component of the Estuary General fishery. This will provide data that can be used to assess how successful management measures have been at rebuilding stocks and maintaining sustainable levels of harvest. It will also be useful as input information in modelling exercises that may be used in the future, particularly if output controls are used in managing the fishery. Catch per unit effort (cpue) data is not a reliable measure of relative abundance for pipis because the species forms dense aggregations so that catch rates can remain high whist abundance on a beach is actually declining. Also, the unit of fishing effort may not be standard and catches may not be representative of all sizes of pipis so that estimates of spawner and recruit abundance are biased. Further, it can be difficult for industry to sample the whole population such that abundances outside fished areas and sizes of pipi clumps remain unknown. Therefore, it is important that a fishery independent strategy be developed to verify patterns from fishery dependent sources and to collect information on those life stages of the pipis not representatively sampled during normal fishing operations. Combining the expertise of fishers with the use of non-selective sampling equipment provides the best opportunity to develop a cost-efficient fisher-independent strategy. Adopting a collaborative approach which incorporates information from fishery-dependent and independent sources gives the best chance of developing an overall cost-efficient sampling strategy. It s important that fishers be included in all aspects of the survey strategy so that they are familiar with the data collected, have confidence in the stock assessment, and are comfortable in discussing management options.
