Spatial distributions of Jonah and Atlantic rock crabs in the Georges Bank and Mid-Atlantic Bight regions during 1968–2021

Abstract Objective The commercial importance of Jonah crabs Cancer borealis and Atlantic rock crabs Cancer irroratus has increased over the past few decades, but both species are still data limited. Objectives were to determine the spatial distributions of Jonah and Atlantic rock crabs over time and to estimate associations with environmental variables. Methods Data were from the Northeast Fisheries Science Center offshore spring bottom trawl surveys during 1968–2021 on Georges Bank and in the Mid-Atlantic Bight. Environmental preferences for temperature (°C), depth (m), and grain size (ϕ) were estimated using generalized additive models, and the habitat usage between the two crabs were compared using empirical cumulative distribution functions. Result The spatial distributions of Jonah and Atlantic rock crabs changed over time. Grain size was the most important environmental variable for predicting presence of Jonah crabs, and depth was the most important variable for explaining presence of Atlantic rock crabs. The generalized additive model with the best cross validation and the lowest Akaike information criterion for both crabs included all environmental, spatial, and temporal variables. Conclusion Jonah and Atlantic rock crabs have different spatial distributions and environmental preferences. Jonah crabs preferred slightly warmer temperatures, deeper depths, and muddier sediments than Atlantic rock crabs. As the commercial importance for Jonah crabs increases, information on their population distribution and habitat usage is important for effective management.