While considerable attention has been directed at ensuring comparability of commercial data over time, it is acknowledged that some recent administrative changes relating to the reporting of catches may have, nonetheless, influenced observed catch and effort trends.
Other uncertainties that arise in this assessment relate to limitations in catch and effort data; mainly in terms of the level of detail provided and the lack of independent verification. The Commercial Catch, Effort and Disposal logbook (formerly the General Fishing Return) was designed to accommodate a diverse range of fishing activities and compromises have been necessary. Consequently, data collection is on a daily rather than operational (set or shot) basis.
In the past, some fishers have experienced problems in correctly interpreting or complying with reporting requirements, especially in terms of effort information reporting. The introduction of new logbooks during the 2007/08 season has helped to clarify reporting, but there is an ongoing need to educate fishers. Further, the lack of catch verification remains an issue.
Catch and effort are influenced by a combination of factors including market-driven fishing operations, changes in resource availability, as well as responses to changing management arrangements. The latter adds further uncertainty regarding the underlying causes of any observed trends in catch and effort. There is, therefore, a need to take account of industry perceptions and information when interpreting fishery dependent information.
Limited information about the recreational fishery remains a major source of uncertainty and is especially significant in the scalefish assessment given that for some species recreational catches appear to equal or exceed commercial catches. Recreational fisher surveys conducted in 2000/01, 2007/08 and 2012/13 provide critical information about this sector. A new state-wide survey undertaken during 2017/18 is considered in this assessment report.
Fish mortality due to disease, predation and fishery interactions with Australian and New Zealand fur seals is largely unknown and represents another source of uncertainty. Seals can cause substantial mortality to some of the fish species assessed in this report. Seals can also cause gear damage and influence fisher behaviour, all of which are factors that impact catches and catch rates. Seal interaction issues tend to be predominantly caused by individual ‘rogue’ seals, which learn to target particular fisheries or fishing methods (e.g. gillnetting), while the typical diet of seals includes mainly pelagic fish species (Goldsworthy et al. 2003).