Zoogeographical subdivision of the pelagic zone of the western Bering Sea based on nekton species ranges

Abstract

The subdivision of the western Bering Sea into zoogeographical regions for nekton fauna was carried out using data from 40 pelagic trawl surveys made by the Pacific Fisheries Research Center. The selected approach involves computer methods for plotting a map that describes the spatial distribution of the index of latitudinal zoning in the form of continuous fields. This index is a digital designation of verbally formulated types of latitudinal species areas. Computer mapping of the region was performed based on generalized data; intraday, seasonal, and interannual time aspects; and trawling depths. According to generalized data, almost the entire western part of the Bering Sea belongs to the high-boreal latitudinal subzone. A small area of the low-boreal subzone occurs only in the southeast of the open part of the sea. The average value of the latitudinal zoning index and its variation significantly decreased with increasing depth. From the upper epipelagic to the mesopelagic layer, the degree of subdivision decreased and the results of zoning of the mesopelagic layer were substantially different from all other zoning results.