Gray Whales (Eschrichtius robustus) Off Sakhalin Island, Russia: Seasonal And Annual Patterns Of Occurrence

Authors

David Weller, Texas A&M University
Bernd Wursig, Texas A&M University
Amanda Bradford, Texas A&M UniversityFollow
Alexander Burdin, Kamchatka Institute of Ecology and Nature Management, Kamchatka, 683000, Russia
Sergey Blokhin, Pacific Institute of Fisheries and Oceanography, Vladivostok, 690600, Russia
Hiroya Minakuchi, Yokohama 245, Japan
Robert L. Brownell Jr., Southwest Fisheries Science Center, National Marine Fisheries ServiceFollow

Date of this Version

10-1999

Comments

Published in MARINE MAMMAL SCIENCE, 15(4):1208-1227 (October 1999).

Abstract

The annual return, seasonal occurrence, and site fidelity of Korean-Okhotsk or western gray whales on their feeding grounds off northeastern Sakhalin Island, Russia, were assessed by boat-based photo-identification studies in 1994-1998. A total of 262 pods were observed, ranging in size from 1 to 9 whales with an overall mean of 2.0'. Sixty-nine whales were individually identified, and a majority of all whales (71.0%) were observed in multiple years. Annual sighting frequencies ranged from 1 to 18 d, with a mean of 5.4 d. The percentage of whales re-identified from previous years showed a continuous annual increase, reaching 87.0% by the end of the study. Time between first and last sighting of identified individuals within a given year was 1-85 d, with an overall mean of 40.6 d. Annual calf proportions ranged from 4.3% (1997) to 13.2% (1998), and mother-calf separations generally occurred between July and September. The seasonal site fidelity and annual return of whales to this part of the Okhotsk Sea emphasize its importance as a primary feeding ground for this endangered population.