Working Group on Surveys on Ichthyoplankton in the North Sea and Adjacent Seas (WGSINS; outputs from 2022 meeting)

The Working Group on Surveys on Ichthyoplankton in the North Sea and adjacent Seas (WGSINS) coordinates several surveys on fish early life stages in the North Sea, Irish Sea and Baltic undertaken for assessment and management purposes. The objectives of WGSINS include review and coordination of these surveys, quality assurance on survey methodology, species identification and provided data and indices, preparation of data for archival as well as identifi-cation of additional objectives that can be achieved by the surveys.

The International herring larvae surveys in the North Sea (IHLS) revealed higher larval abun-dances around the Orkneys, lower abundances in the Buchan and Banks area and large numbers of Downs larvae.

The 2022 North Sea Midwater Ring Net survey (MIK) was faced with numerous challenges (weather, Covid-19 and technical issues) resulting in poor coverage, but data tests showed that the herring 0-ringer index was still reliable, although one of the lowest in the time series.

The Downs recruitment survey (DRS) in April 2022 showed comparable numbers and spatial distribution of herring larvae as in 2021. As sampling should only be done at night, additional survey participation is required. A WGSINS sub-group is planned for 2023 to discuss the way forward with the DRS survey and index calculations.

The Northern Irish Northeastern Larvae survey (NINEL) in November 2021 showed similar spa-tial distributions as in previous years and relatively high larval abundances.

The 2022 Northern Ireland MIK survey (NI-MIK), targeting different juvenile gadoids, was af-fected by a change in survey timing and mechanical issues. No juvenile cod were caught and catches of haddock and whiting were low.

The N20 recruitment index of the 2021 Rügen herring larvae survey (RHLS) was more than 10 times higher than the record low value in 2020 and the highest value since 2015, but still below the long-term average.

The Baltic Ichthyoplankton Surveys (BIS) are a series of several individual surveys, providing an SSB estimate and a recruitment index for Eastern Baltic cod. Sample analyses for 2022 are still ongoing, but preliminary data indicate that SSB remains at a similarly low level as in 2018-2021.

In addition to the surveys and target species/stocks mentioned above, WGSINS provides a forum to present and discuss additional work conducted on these surveys and on other, dedicated pilot surveys. A pilot survey aiming to establish a larval recruitment index for North Sea sprat showed promising results but broader area coverage would be an advantage. Another pilot study on recently hatched sandeel larvae analyzed spawning areas and larval drift in the North Sea, which may help to re-define management areas.

Apart from the data needed for the original survey objectives, ichthyoplankton surveys can pro-vide additional information and data products, e.g. on eggs and larvae of non-target species and other organisms like jellyfish and zooplankton as well as marine litter. WGSINS will continue to collect and archive this information which is underrepresented in traditional fishery survey da-tasets and may thus contribute to the implementation of an ecosystem approach to fisheries man-agement.