Merging Acoustic and Reproductive Data with Dispersal Models to Improve Recruitment Indices in European Anchovy

Numerous studies have demonstrated the relationship between the hydrodynamics and the advection, dispersion and recruitment of small pelagic fish. However, the lack of data has often conditioned the use of realistic locations for the model setup and configuration in transport studies. Using the European anchovy in the NW Mediterranean as a case-study, we will show i) the relevance of the realistic initial position of the eggs to the coastal recruitment of late anchovy larvae and ii) the possibility to use routinely acquired acoustic survey data, plus fecundity data, to derive those initial positions. Further, we will show the results of an application of a Spatially-Explicit Individual-Based model (SEIBM) to infer the effects of inter-annual variability in spawning behavior, larval and ocean dynamics on the transport from the spawning (Gulf of Lions) to the late-larval recruitment areas. The SEIBM includes changes in eggs buoyancy, larval vertical migration and temperature-dependent growth. We demonstrate that the spatial paths of larvae differ dramatically between years and that the connectivity in the NW Mediterranean is mainly southward. The adjustment between estimated recruited late-larvae and fish landings showed a high accuracy. Our simulations are coherent with existing recruitment proxies and open new possibilities for fisheries management.