A proposal for a Research Plan to Determine the status of the Key Shark Species

Citation
Clarke SC, Harley SJ (2010) A proposal for a Research Plan to Determine the status of the Key Shark Species. WCPFC, Nuku’alofa, Tonga; and Majuro, Republic of Marshall Islands
Abstract

The Fifth Regular Meeting of the Scientific Committee (SC5) of the Western and Central Pacific Fisheries Commission (WCPFC) in August 2009 considered the feasibility of quantitative stock assessments for sharks and recommended that preliminary assessments should proceed in parallel with development of a shark research plan to fill data gaps. This paper presents a proposed shark research plan in response to the Commission's approval in December 2009 of SC5's recommendation. An introduction to the Commission's eight current key shark species is presented, including a brief review of the history of their designation and species profiles containing information on habitat, life history and ecological risk, conservation status, current catches in the WCPO, and existing assessments or management. A review of existing fishery and biological information is then presented and data gaps are summarised. Major difficulties in the use of logsheet data for shark assessment are anticipated due to lack of data provision, as well as issues of species misidentification, under-reporting and changes in targeting strategies. Observer data coverage, especially for longline fleets, is low and may not be representative of all areas where sharks are caught. Other commercial, research and recreational fishery data sources have some potential to inform the analyses but will require further work. Fishery-specific biological data are available mainly in the form of observer data on shark lengths, sex, fate and condition, and through a limited number of studies on bycatch mitigation methods (i.e. post-release mortality rates). It is concluded that there is a reasonable amount of information available on the biology of most key shark species although studies are concentrated in a few geographic regions. The extent of shark tagging data is difficult to characterize but appears primarily available for blue and mako sharks. A number of proposed shark assessments by other organizations were noted, including silky and oceanic whitetip assessments for the eastern Pacific Ocean by IATTC; assessments of blue, mako and potentially bigeye and pelagic threshers by ISC; and data compilation for makos by CSIRO. A research plan is proposed as three phases: assessment, research coordination and fishery statistics improvement. Progress in all three phases will be necessary to assist the commission in meeting its responsibilities for ensuring the sustainability of shark stocks. Phase 1 consists of three assessment steps to be undertaken on the basis of existing data. The first step will involve constructing indicators of the degree of fishing pressure on the key shark species. The second step will involve plotting these indicators against various measures of shark species' productivity. The third step will involve stock assessments using simple surplus production and age structured models, if possible. However, without additional inputs from Phases 2 and 3, stock assessments for some species will be severely compromised and may not be able to provide a meaningful basis for Commission decision-making. For this reason CCMs are invited to consider potential activities identified under Phases 2 and 3 (i.e. research coordination and fishery statistics improvement) as collaborative work and in-kind contributions.