Potential future climate-induced shifts in marine fish larvae and harvested fish communities in the subtropical southwestern Atlantic Ocean

The continental shelf in the southwestern Atlantic Ocean is among the six richest marine regions for biodiversity in the Southern Hemisphere, and its subtropical region is one of the fastest-warming hotspots. Thus, climate change could profoundly affect future species distributions. We investigated future climate-induced changes in fish larvae and harvested fish taxa in the subtropical southwestern Atlantic Ocean using a community-based modelling technique (gradient forest). This approach integrates information on multiple species rather than treating each species individually, as is typical in many species distribution approaches. We addressed two primary questions: how might climate change affect fish larval communities, and will communities of harvested fish (juveniles and adults) taxa respond similarly. Using two climate change scenarios (moderate RCP 4.5 and ‘business as usual’ 8.5), we found that fish larvae and harvested taxa are influenced differently by environmental variables, with differences in both the level and shape of the response to environmental drivers. Chlorophyll a and sea surface temperature were the most important predictors for fish larvae communities, while depth and sea surface salinity best predicted the harvested community. However, both communities are expected to move southwards in response to climate change, with greater changes in community composition predicted in the southern portion of the study area for both fish larvae and harvested taxa. To our knowledge, this is the first study to investigate the effect of future climate change on a suite of taxa of fish larvae and adults. We also suggest that modelling the integrated response of a suite of species to environmental predictors using community-modelling approaches such as gradient forest could provide robust projections and novel insights into community changes.