Examination of saffron cod Eleginus gracilis (Tilesius 1810) population genetic structure

Abstract

Annual ice retreat in the northern Bering and Chukchi seas, which has occurred earlier in the past decades resulting in longer ice-free seasons and warmer ocean temperatures, is producing a cascade of ecological effects, and may open Arctic waters to commercial fishing and oil exploration. Baseline knowledge of population structure of a species is critical to developing strategies for management and conservation. There is little information for the saffron cod (Eleginus gracilis), an abundant forage fish inhabiting the coastlines of the North Pacific and Arctic oceans. We examined saffron cod population genetic structure with data from nine microsatellite loci designed to describe the genetic compositions of and variation among 40 collections of saffron cod from four regions (northwestern Alaska, Gulf of Alaska, western Pacific Ocean, and Gulf of Anadyr). The northwestern Alaska collections (Norton Sound and Chukchi Sea) exhibited little genetic divergence. The Gulf of Anadyr collection differed from other regions but was most similar to those of northwestern Alaska. The collections from the western Pacific Ocean (Sakhalin Island and Hokkaido Island) differed genetically, but not to the extent they did from other regions. Gulf of Alaska collections (Kodiak Island and Prince William Sound) comprised a lineage that was distinct from all of the other areas, including the geographically adjacent northwestern Alaska collections. The absence of genetic structure in northwestern Alaska probably reflects their recent expansion into previously unavailable habitat that became available after the Last Glacial Maximum (~ 16,000 years ago). Tracking and predicting the likely expansion of the eurythermal saffron cod may have parallels to its postglacial colonization.