Divergent Environmental Niches and Climate Vulnerabilities of Jonah Crab ( Cancer borealis ) and Atlantic Rock Crab ( Cancer irroratus )

ABSTRACT Jonah crab and Atlantic rock crab in the United States are currently assessed by National Oceanic and Atmospheric Administration climate change vulnerability assessments under the category Cancer crabs due to a dearth of species‐specific information across the attributes assessed. These species are frequently bycatch in the American lobster fishery and have low landed volume in comparison to larger Northeast US commercial fisheries. Here, we developed species distribution models using abundance, bottom temperature, and bottom salinity from Northeast Fishery Science Center Bottom Trawl data and calculated species‐specific environmental suitability indices. We used interpolated data to hindcast (1992–2024) environmental suitability in the five Jonah crab stocks for each species. Then, using similar methods, environmental suitability was forecasted from bottom temperature and bottom salinity conditions from 2075 to 2094 under RCP 8.5 climate conditions. This analysis found that Jonah crab occupies a narrow, stable niche, with optimal temperatures of 9°C–12°C in both seasons and habitat 150–350 m deeper than Atlantic rock crab, while Atlantic rock crab tolerates far larger swings, with the OSNE stock shifting optimal temperature by 11°C (5°C to 16°C) and salinity by 7 units between spring and fall. By identifying these differences, we show that Jonah crab's narrower thermal and salinity tolerance likely makes it more sensitive to climate change than the broadly tolerant Atlantic rock crab, refining species‐specific inputs for climate change vulnerability assessments and each species' potential as a long‐term fishery target.