Satellite Tags Track Pacific Cod Shifts in Warming Bering Sea

Pacific cod support Alaska's second-largest groundfish fishery and play a critical role in the Bering Sea ecosystem. From 2017 to 2019, the Bering Sea experienced unusually warm temperatures and minimal sea ice, conditions that appear to have shifted Pacific cod distributions farther north compared to colder years, raising questions about long-term changes in population distribution and demographic structure.

A satellite tagging study launched in 2019 is now generating data to help answer those questions, with direct implications for stock assessments and sustainable management of the fishery.

The tagging study was led by Dr. Susanne McDermott, the Gulf of Alaska bottom trawl survey lead, and included fisheries biologists Julie Nielsen and Kimberly Rand, among others. McDermott described the uncertainty that drove the research: "There was tremendous anxiety over what's going on. Why are these fish in different places? Is this something that's changing on a population level? Is this just the same population moving into different areas?"

The research aims to determine whether recent shifts in cod distribution represent long-term changes or temporary movements, providing data that stock assessments depend on for sustainable management of the groundfish fishery.

Understanding whether the same population is simply moving into different areas, or whether something more fundamental is changing at the population level, is central to the study's purpose. The stakes extend to Bering Sea and Aleutian Islands fishing fleets, processors, coastal communities tied to cod revenue, and northern communities watching ecosystem shifts affect subsistence resources, all of whom depend on accurate distribution and abundance data feeding into management decisions.