Population structure and distribution of Gadiformes in the subarctic northeast Pacific

Gadiformes is one of the major taxa in the subarctic seas of the northeast Pacific Ocean, a region with significant high-latitude fishery production. However, little is known about Gadiformes species within these waters. Distribution and abundance fluctuations of Gadiformes are closely linked to shifts in the marine environment, and play a crucial role in maintaining ecosystem structural stability of high-latitude regions. This study examined the community composition and spatiotemporal distribution of Gadiformes in four major subarctic regions within the northeast Pacific (Aleutian Islands, Bering Sea shelf, eastern Bering Sea, and Gulf of Alaska) using bottom trawl survey data from the Alaska Fisheries Science Center (AFSC). Gadiformes diversity was assessed using ecological approaches such as diversity indices and cluster analysis, and the relationship between catch-per-unit-effort (CPUE) of the three dominant species and depth, sea surface temperature, and bottom temperature was examined using a generalized additive model (GAM). A comparative analysis was carried out for the cold years (2010/2011) and warm years (2015/2016) to investigate the influence of bottom water temperature on the dominant species. The results indicated that 13 species of Gadiformes from 4 families and 9 genera were present in these subarctic regions, with the dominant species being Gadus chalcogrammus, G. macrocephalus and Albatrossia pectoralis. Additionally, the distribution and abundance of these dominant species showed clear spatial patchiness, with G. chalcogrammus and G. macrocephalus mainly occurring on the eastern Bering Sea shelf, whereas A. pectoralis was primarily distributed in deeper waters. In addition, A. pectoralis exhibited totally higher abundance than the other two species. The GAM results indicated that bottom water temperature was the most influential variable, followed by depth and spatial location, with nonlinear relationships observed between CPUE and environmental factors. Comparing cold and warm years, the abnormal warming of seawater during the warm years expanded the suitable habitat area for G. chalcogrammus and G. macrocephalus, with increasing abundance, whereas habitat distribution and abundance of A. pectoralis exhibited almost no change. This study provides further understanding of Gadiformes distribution and species response to environmental change in the subarctic seas of the northeast Pacific.