Walleye Pollock in the Western Arctic Seas: Analysis of Current Occurrence and Modeling of Future Distribution

Under climate change manifested as Arctic amplification, the intrusion of alien species into high latitudes is observed, transforming the structure of marine ecosystems. This paper presents an analysis of the current occurrence and modeling of the potential future distribution of walleye pollock Gadus chalcogrammus (Gadidae) in the Western Arctic seas, primarily the Barents Sea. The aim is to assess the spatial potential for the species’ dispersal in the context of ongoing and projected oceanographic changes. Based on data from the Polar Branch of VNIRO (2000–2025), literature sources, and international databases, information on pollock occurrence from the Bering Sea to the Barents Sea was compiled. Ensemble species distribution modeling (SDM) using the biomod2 package in the R environment was applied to analyze environmental drivers and predict distribution. Bioclimatic layers from the Bio-ORACLE repository (current and projected up to 2100) corresponding to three SSP (Shared Socioeconomic Pathways) emission scenarios were used as predictive variables. Since the beginning of the 21st century, the frequency of pollock occurrence in the Barents Sea has increased, with 23 individuals recorded in 2021–2024, mainly in eastern areas. Modeling revealed that bottom temperature, salinity, and oxygen concentration are key factors determining pollock distribution. The species exhibits narrow optima for temperature (approximately 3.8°C) and salinity (32.4‰), which significantly distinguishes it from the dominant native species of the Barents Sea: Atlantic cod and haddock. Under current conditions, up to 75.1% of the Barents Sea area may be potentially suitable, but the strict salinity requirements are the main limiting barrier for its naturalization. Predictive modeling until the end of the 21st century did not reveal a significant expansion of favorable areas even under substantial warming scenarios. The most favorable conditions will persist in the Chukchi Sea and some parts of the Barents Sea determined by the salinity regime of Atlantic water masses. Under moderate and intense warming, a “corridor” with suitable conditions may form through the Siberian Arctic seas, potentially connecting the Chukchi and Barents Sea groupings.