Working Group on Surveys on Ichthyoplankton in the North Sea and Adjacent Seas (WGSINS; outputs from 2024 meeting)

The Working Group on Surveys on Ichthyoplankton in the North Sea and adjacent Seas (WGSINS) coordinates surveys on fish early life stages undertaken for assessment and management purposes. The objectives of WGSINS include review and coordination of these surveys, quality assurance on survey methodology, species identification, provided data and indices, preparation of data for archival, as well as identification of additional objectives that can be achieved by the surveys. WGSINS coordinates seven surveys, three in the North Sea (IHLS - International herring larvae surveys in the North Sea, MIK - North Sea Midwater Ring Net survey, DRS - Downs recruitment survey), two in the Irish Sea (NINEL - Northern Irish Northeastern Larvae Survey, NI-MIK - Northern Ireland MIK Survey) and two in the Baltic (RHLS - Rügen herring larvae survey, BIS - Baltic Ichthyoplankton Surveys). Most surveys target herring larvae from various stocks, while the NI-MIK targets pelagic juvenile gadoids and the BIS eggs and larvae of Eastern Baltic cod. At WGSINS 2024, cruise summaries and results from the seven surveys were presented. All relevant estimates and indices from the surveys were updated, and data were uploaded into the ICES eggs and larvae database. New methodologies to incorporate the DRS into the MIK recruitment index time-series were discussed, concluding that these can provide improvements to the existing MIK index. These recent developments will be presented to the Herring Assessment Working Group (HAWG). The chair of WGELFADG and representatives from the ICES Data Centre presented updates regarding the ICES eggs and larvae database. Members of WGSMART presented updates with focus on the egg and larvae module in SmartDots. Several topics concerning the standardization of sampling and sample processing procedures were discussed, including updates to the survey manuals, species identification, sub-sampling & treatment of damaged larvae. WGSINS provides a forum to present and discuss additional information and data products that can be provided by ichthyoplankton surveys, such as investigations on non-target ichthyoplankton species, other organisms like jellyfish and zooplankton, or marine litter. Several presentations highlighted the potential of ichthyoplankton surveys to provide added value, improving our understanding of pelagic ecosystems and contributing to stock assessment and management. This included e.g. sampling of cephalopod early life stages to identify spawning and nursery areas and the concept of a “holistic approach”, aiming to combine data from various surveys on different life stages to obtain a more holistic understanding of the life cycle of a specific species in time and space. A major goal of WGSINS is to assess possibilities for the different ichthyoplankton surveys to supply ecosystem data to support the implementation of an ecosystem approach to fisheries management. Thus, tables with “Overviews of additional information collected on ichthyoplankton surveys coordinated by ICES WGSINS” were compiled, providing comprehensive information on all presently ongoing additional sample and data collections on the surveys coordinated by WGSINS. WGSINS will continue to collect and archive additional information, underrepresented in traditional fishery survey datasets, aiming to contribute to the implementation of an ecosystem approach to fisheries management.