Catch and effort data obtained from commercial logbooks is the primary source of information used as an index of abundance for most SESSF species. The assumption underlying this is that commercial catch rates change in a linear fashion with abundance. This assumption, however, has little independent support for many SEF species and is frequently criticised by industry and scientists alike. One of the most significant problems with commercial CPUE data in the SEF is that fishers modify their fishing practices to suit quota availability and market demands. Also, many fishermen only put the retained catch in logbook data, not the total catch. Furthermore, the influence of environmental conditions on fish availability also reduces the effectiveness of CPUE as an index of abundance. Low or bycatch TACs also prevent catch rate data being used as an index of abundance.

Implementation of a fishery independent survey is the most cost-effective and feasible means to get an independent index of abundance for the suite of SESSF species.

Recognising this, the SESS Fishery Assessment Group (SESSFAG) has placed highest priority on the need to implement fishery-independent methods for surveying relative abundance of SESSF fish stocks.