A note on the spatial distribution of western gray whales (Eschrichtius robustus) off Sakhalin Island, Russia in 1998

Abstract

Three aerial surveys were conducted along a portion of the northeastern coast of Sakhalin Island, Russia between August and September 1998. They were conducted to examine the spatial distribution of western gray whales on their feeding grounds, and in relation to current and planned industrial activity. A total of 32 gray whale groups, consisting of 38 whales, was sighted during the surveys. Group sizes ranged from 1-3 individuals (mean = 1.2, SD = 0.54), with 87.5% (n = 28) composed of single whales. All groups detected were within 5km of the shore and 93.8% (n = 30) were sighted inside 4km. Sighting locations ranged from 0.6-4.8km offshore, with an overall mean distance from shore of 2.5km (SD = 1.11). These data suggest that western gray whales feed primarily in waters less than 20m deep and relatively close to shore. The nutrient-rich effluent from a large coastal lagoon is believed to significantly enrich the near-shore benthic environment of the northeastern Sakhalin Island coast, creating an area of particularly high food availability, and in turn contributing to the near-shore affinity of gray whales observed during this study.