Authors: Rich Bell, Brian Grieve, Marta Ribera

Climate change is altering the distribution and abundance of fish species in ways not anticipated by current management policy. We developed products to inform sustainable fisheries management by creating spatially-explicit, dynamic models of marine habitats that can inform stock assessments for twenty-five commercially important species on the Northeast Shelf. Improving upon methods used in the 2014 Butterfish stock assessment, we expanded the dimensions of habitat included in the models by integrating substrate, and seabed features along with the dynamic properties of the water column that change on daily to decadal time scales.
Changes in climate mediated habitat can affect the index of abundance from trawl surveys by altering catchability (q), the proportion of total biomass of a species caught in a trawl survey. Fisheries independent trawl survey data are the backbone of many stock assessments for species on the northeast shelf. Catchability is a function of availability, the proportion of total biomass within the space-time footprint of the trawl survey and detectability, the proportion of biomass within the path of a survey gear that is caught in the survey gear. The sample design for most surveys are stratified randomly over space, although they actually sample over time and space. Trawl surveys in the northeast often sample in the spring and fall when water temperatures are changing dramatically and species are migrating offshore and onshore. A single seasonal survey for the NEFSC trawl survey can span two months, during which time there can be dramatic changes in the oceanographic conditions and the location of migrating organisms. 

While studies examining species temperature envelopes and projecting them into the future have been done, they have rarely been explicitly developed to inform stock assessments or combined both the water column and seafloor to get a true picture of climate induced habitat changes. The goal of this work was to provide direct benefit to management by identifying changes in the availability of populations to fishery independent surveys. In an attempt to provide a broader ecological perspective we used a mechanistic thermal response model as well as developed ecological benthic features to better consider the relationship between fish and the sea floor. 

We combined data from the Northeast Fishery Science Center (NEFSC) trawl survey, the NorthEast Area Monitoring and Assessment Program survey (NEAMAP), State surveys and the benthic information from the NorthWest Atlantic Marine Ecoregional Assessment (NAMERA), to determine the mechanistic thermal-benthic habitat response curve for each species, and map out the spatial extent of the suitable habitat for different years and seasons with regional ocean models. 

The research seeks to improve the understanding of the impacts of climate variability and change on habitat which directly regulates the abundance and distribution of managed fish stocks. Our intent is to utilize these current and historic data sets to improve the synthesis, analysis, and application of climate and marine ecosystem observations and monitoring information to improve fisheries management.

Read summary report, with description of methods and results.