Predicting Pacific cod thermal spawning habitat in a changing climate

Warming temperatures elicit shifts in habitat use and geographic distributions of fishes, with uneven effects across life stages. Spawners and embryos often have narrower thermal tolerances than other life stages, and are thus particularly sensitive to warming. Here, we examine the spatiotemporal variability of thermal spawning habitat for Pacific cod in the eastern Bering Sea. Specifically, we use bottom temperatures from downscaled global climate models coupled with an experimentally-derived hatch success and temperature relationship to predict how the spatial extent, mean latitude, and consistency of thermal spawning habitat has varied over time. Predictions are validated with observations of spawning adults and early larvae. We find that habitat availability has not increased in the past but is predicted to increase and shift northward in the future, particularly if no climate change mitigation occurs. Habitat hotspots are consistent across shorter time periods but do shift across the shelf by the end of the century such that highly suitable areas in the past and present are not predicted to be suitable in the future. This work highlights the importance of coupling experimental data with climate models to identify the complex and mechanistic dynamics among temperature, life histories, and ecology, particularly under climate change.