SEAwise report on historic and future spatial distribution of fished stocks

This SEAwise report assesses the distribution of fish species across European seas. To this end, an ICES workshop, WKFISHDISH2, was co-organised to reach out to the broader scientific community and acquire as much knowledge as possible on scientific surveys and species distribution models. A large amount of historical scientific survey data, stored in the DATRAS and MEDITS databases, served as basis for the development of guidelines on how to appropriately pre-process such data, analyse them with state-of-the-art species distribution models (SDMs), and define metrics on how to compare species distributions. Distribution maps were generated separately for the Mediterranean Sea and the Northeast Atlantic spanning the Baltic Sea, North Sea, Celtic Seas, Bay of Biscay and Iberian Coast. In general, there was good agreement between the distributions generated by different models that were applied to four different reference species with different characteristics in terms of spatial distribution. Differences between models were mainly related to the configuration of spatiotemporal processes, and the extrapolation, mainly in areas with few observations, or where correlates extend to values outside the observed range. Trends in species distribution were species specific. Some species have shifted in a northward direction, while the distribution of other species was static, or characterized by a southward trend. It is difficult to have a mechanistic understanding, e.g. migration due to climate change, local outbursts, and/or local depletion of fish stocks, of these changes based on survey data that does not allow tracking of individual fish. Potential climate related shifts were instead investigated by linking the survey data with oceanographic variables generated through coupled hydrodynamic-biochemical models. This allowed us to explore how species distributions may change under different scenarios of climate change. More information about the SEAwise project can be found at www.seawiseproject.org