Climate-induced habitat changes in commercial fish stocks

Climate change is altering the distribution and abundance of fish species in ways not anticipated by current management policy. We created spatially explicit, dynamic models of marine habitats that can inform stock assessments for 25 commercial species on the US Northeast Shelf. The habitat models integrated substrate and seabed features along with the dynamic properties of the ocean. Changes in climate-mediated habitat can affect the survey results by altering the availability component of catchability. Changes in availability were examined (1980-2014) by combining species distribution models with hindcast ocean models. Three patterns in availability were evident: (1) the availability for most species varied over time with no trend; (2) for a number of estuary-dependent species, availability varied with no trend and then dropped dramatically in 2009 when the federal trawl survey changed vessels; and (3) for a set of mid-depth, non-estuary dependent species, availability showed a continuous decline over time. There were few changes in dynamic habitat as the bottom water temperature did not exhibit a strong trend over the time-period studied, resulting in little climate-attributed changes in catchability. Changes in survey design can also have dramatic impacts on catchability, highlighting the method's ability to detect both climate driven and survey driven changes in catchability.