Report for Project 78: Analysis of Observer and Logbook Data Pertaining to Key Shark Species in the Western and Central Pacific Ocean
This paper presents an analysis of data for sharks caught in longline and purse seine fisheries in the Western and Central Pacific Ocean (WCPO) held by The Pacific Community – Oceanic Fisheries Programme (SPC-OFP). It represents the final report of WCPFC Project 78 (Review of shark data and modelling framework to support stock assessments).
Overall the quality, with respect to the key shark species, of logbook data currently held by SPC has been improving over time. The logbook data has increasing levels of spatial coverage and higher levels of reporting sharks to species. For both the longline and purse seine fisheries the logbook data is useful to support analytical and indicator assessments.
Similarly, the quality of the observer data currently held by SPC is better in recent years than the historical data. Observer data coverage has required to be 100% in the purse seine fishery since 2010, but the data available do not represent 100% coverage, similarly the available data do not reach the required 5% coverage level in the longline fishery. Coverage, as a percent of total effort, has been increasing over time and has also increased in spatial coverage. In general, these data can support analytical (or indicator) assessments for the more commonly caught species but would require significant extrapolation to assess the less common species.
Reporting of logsheet data by fleet is highly variable, with many fleets reporting significantly less than 100%. It is difficult to identify whether logsheet data are provided for all key species given that non-reporting may be a result of a zero catch event (e.g. whale sharks in the longline fishery) or a lack of reporting. The relationship between the observer and logsheet reporting and the logsheet and aggregate reporting affect the precision in estimation of catch and potentially other stock related metrics such as distribution. Comparison of observer and logsheet data highlights that there is a large discrepancy in the rate of non-species-specific recording in the longline fishery logbook data pertaining to sharks. It is important to note that historic logbook recording did not have the provision for reporting the key shark species as there was no obligation to report to species level. There are historical logbook data that SPC does not hold and may have been useful for this study, noting that historic operational logbook data may be subject to similar non-reporting of sharks. The general recommendation is for fishers to receive further identification training to improve the provision of shark interaction information to the species level. This is especially important for manta and mobulid rays which are commonly recorded only to the generic level. Recently the Western and Central Pacific Fishery Commission listed manta and mobulid rays as key sharks . In adopting manta and mobulid rays as key sharks the Commission also noted that data gaps would likely preclude traditional assessment methods and that revision of the minimum reporting standards should be undertaken due to the lack of data for these species. Correspondingly, this report does not generate new results for manta and mobulid rays, but refers to the SC 12 document on non-key sharks including manta and mobulid rays.