Density dependence modulates climate change impacts on eastern Bering Sea snow crab

Abstract Populations change as a result of many interacting processes, each of which may be moderated by density dependence and/or climate. Models and projections of population dynamics support conservation and economic planning, but the extent to which the influence of climate or density is incorporated varies. We develop a population dynamics model for eastern Bering Sea snow crab ( Chionoecetes opilio ) that fits to data collected from 1982 to 2023 to estimate variability in recruitment and mortality. We then use generalized additive models (GAMs) to explain the variability in recruitment, mortality and maturity using environmental covariates and density. Finally, we project the population forward under various assumptions about climate and density dependence on recruitment, mortality and maturity. Feedbacks among population processes result in different short‐ and long‐term population trajectories. For example, including density dependence in mortality projections allows for a stronger rebound in the population in the short term, but the harmful effects of warming outweigh the protective effect of lower density in the long term. Projected long‐term crab abundances were much lower than historically observed under receding ice cover in the Bering Sea regardless of the combination of processes driven by density and climate. Synthesis and applications . Our results underscore the need for management capable of addressing the impacts of both density and climate effects on multiple processes in harvested populations. Non‐stationarity in drivers of population dynamics (e.g. climate change) will further affect the ability of management to achieve sustainable yields. Current frameworks built around equilibrium‐based maximum sustainable yield are not well‐suited to address either of these issues.