Abstract
Summary Objective: Changes to quota and bycatch regulations in skate fisheries, or fisheries that take skate as bycatch, have increased the incidence and level of discarding. A proportion of discarded skates will die. Research on thornback ray (Raja clavata) has shown that a number of factors (such as tow duration, gear type and catch weight) affect levels of discard mortality, which may rise as high as 40%, but will vary between areas, species and fishing practices. Estimates of discard mortality of skates are therefore uncertain, and hamper the assessment of stock status, the development of appropriate mitigation measures, and recommendations of good fishing practice. To develop robust assessments of the risks to stock sustainability that discard mortality poses, it is necessary to identify the skate species discarded in representative UK fisheries, their condition and discard survival. The research should focus on those fisheries that account for a high proportion of UK skate landings and, as priority, for those species/stocks of greatest management concern. It is also desirable to collect more information for species or fisheries for which there are no or only limited data on the survivorship of discards. These estimates should be combined with information on the distribution and activity of those fisheries that exploit them. Key Customer Purpose: Estimates of skate survivorship after discarding, and the factors that contribute to its variability, can be used to evaluate the potential fisheries-induced mortality on skate populations and assess the risks to stock sustainability of continuing with current fishing practices. The information will also inform discussions on the benefits to stock conservation of size restrictions, MPA or seasonal closures, and other technical measures, such as gear modification or recommendations on best fishing practice. Specifically, the results will be used by ICES Working Group on Elasmobranch Fishes (WGEF), at international fisheries negotiations (specifically current TACs and quotas discussions on elasmobranchs); in negotiations with regional fishing management organisations; e to support the future EC Plan of Action for elasmobranchs; and to address international conservations agreements (e.g. Convention on Biological Diversity). The benefits of improved estimates of discard mortality will be to reduce the risk that unsustainable fishing practices or quotas will damage stock health and potential. In addition, it will benefit the development of any proposed recovery plans for threatened stocks. Furthermore, the research would highlight where improvements could be made to fishing practices to reduce discard mortality, but without requiring punitive quotas or over-regulation of the industry.
United Kingdom