Improving Herring Recr Surveys IHeRS (KB-36-002-017)

Recruitment is the main driver of fish stock dynamics. It is also one of the more difficult parameters in biology to get a good grip on. Within the North Sea, two surveys are on-going that sample herring larvae and can be used to generate a proxy of recruitment for Autumn spawned larvae. The Downs Recruitment Survey (DRS) has been added in 2018, 2019 and 2021, providing recruitment information on the winter-spawned larvae. The ICES Herring Assessment Working Group (HAWG) looks positive on these results to incorporate in the herring assessment in the future. There are however some questions of the new DRS about the differences in sampling compared to the IBTS-MIK, due to survey time constraints. This project will provide information on the effect of day versus night sampling, the use of a blue midwater ring trawl, and effect of water currents on the sampling of larvae. These results will allow providing an improved proxy of recruitment for North Sea herring.