Changes in albacore tuna habitat in the northeast Pacific Ocean under anthropogenic warming

Abstract

AbstractAlbacore tuna are widespread in the North Pacific Ocean and the basis of an important commercial fishery. These fish live mainly within a fairly narrow thermal niche range defined by sea surface temperature (SST) isotherms between 14 and 19°C. Because the fish's thermal range coincides with strong latitudinal temperature gradients off the northwest coast of North America, there is a great deal of seasonal and interannual variability in the distribution of these fish, and a significant potential for a new habitat in this region with anthropogenic climate change. We use historical catch and effort data from the Canadian troll fleet to define the fish's thermal niche, and document observed shifts in distribution associated with interannual climate variability. We then use an ensemble of climate model simulations from the Coupled Model Intercomparison Project to estimate northward extension of the potential habitat under anthropogenic warming scenarios. A potential new habitat is about half a million square kilometres even under a moderate mitigation scenario. Estimates are smaller for some months of the year in which the fishery is conducted, but as well as opening up new regions, the length of season in which the fishery is active may be extended in the northern part of the range. However, much of the potential new habitat will be in oceanic waters with relatively low productivity. Our estimated area of potential habitat is based on the fish's thermal niche and assumes that other biologically important factors such as food will not be limiting.