Suchergebnisse

This study quantifies potential size selection of a fish and a crustacean species in di-amond mesh codends during a fishing process. Changes in mesh geometry along the codends and at different catch weights were recorded in a flume tank and subse-quently used together with the morphology of cod (Gadus morhua) and Nephrops (N. norvegicus) to simulate potential size selection. By assuming certain patterns of fish escape behaviour in the codend, it was demonstrated that it was possible to replicate results for size selection based on sea trials with similar codends. Results show that L50 can increase significantly with increasing catch weight at the aft end of the codend where most of the selection is known to occur. The results document the var-iation in potential size selection along a codend during a catch-build-up. It is empha-sized that experimental studies aiming at describing the selectivity in different types of codends in a commercial situation, need to be based on catch levels representative for the commercial levels to prevent underestimation of the selectivity in the system, especially for designs to be included in the legislation. It was additionally noted that escapement happens mostly in the area of catch accu-mulation. In response to questions, it was also noted that FISHSELECT methodology has been used. Mesh penetrations were simulated for each individual. Considering the relationship between catch weight and codend selectivity, studies with lower catches can underestimate size selection in commercial conditions

The potential for exemption from the European Union (EU) Common Fisheries Policy's (CFP) landing obligation (discard ban), where high discard survival can be demonstrated, has identified the need for scientific guidelines to conduct discard survival assessments. Robust estimates of discard survival can be used to justify exemptions from the landing obligation and inform on levels of post-release fishing mortality, which can then be accounted for in stock assessments. The Working Group on Methods for Estimating Discard Survival (WGMEDS) set out to review and update ICES guidance on Methods to Estimate Discard Survival and complete meta-analyses of discard survival evidence to investigate variables influencing survival, with a view to influencing survival through modified fishing practices. We also explored the demand for ongoing monitoring requirements to inform on discard survival and took a proactive approach to sharing discard survival estimates with those working in stock assessment so that new evidence could be applied more widely. In the past three years, the considerable investment in research in to discard survival, specifically from EU countries, has continued. The main outputs from WGMEDS include enhancements to the ICES guidance on how to quantify discard survival. This has supported the work of group members to estimate discard survival in a variety species-fishery combinations, including Nephrops, mackerel, plaice, common sole, eels, rays, much of which has been put forward as evidence to support exemptions from the EU discard ban. A critical review framework developed by WGMEDS has been used by the EU Scientific, Technical and Economic Committee for Fisheries (STECF) to assess the quality of discard survival evidence for proposed exemptions. There has been a high impact of work produced by the members of the group – specifically in multiple new EU regulated exemptions from the landing obligation. This has permitted fishers to continue discarding defined species and so assisting the implementation of the EU discard ban. Future work is expected to focus on applying discard survival estimates in stock assessments. This would include developing guidance to assist assessment expert groups to determine whether available survival studies can be applied. It would require reviewing and assessing the quality and confidence in available discard survival estimates and exploring the potential to combine the results of survival studies so the effect of different variables could be accounted for in estimating an overall best survival estimate. Ultimately, we would aim to include estimates of discard survival in catch scenarios in the ICES advice sheets.