Southwest Fisheries Science Center, National Marine Fisheries Service, P. O. Box 271, La Jolla, CA 92038, U. S. A.
GRAY WHALES (ESCHRICHTIUS ROBUSTUS) OFF SAKHALIN ISLAND, RUSSIA: SEASONAL AND ANNUAL PATTERNS OF OCCURRENCE1
Article first published online: 26 AUG 2006
Marine Mammal Science
Volume 15, Issue 4, pages 1208–1227, October 1999
How to Cite
Weller, D. W., Würsig, B., Bradford, A. L., Burdin, A. M., Blokhin, S. A., Minakuchi, H. and Brownell, R. L. (1999), GRAY WHALES (ESCHRICHTIUS ROBUSTUS) OFF SAKHALIN ISLAND, RUSSIA: SEASONAL AND ANNUAL PATTERNS OF OCCURRENCE. Marine Mammal Science, 15: 1208–1227. doi: 10.1111/j.1748-7692.1999.tb00886.x
We dedicate this paper to Ken Norris, a pioneer and leader of research on the behavioral ecology and conservation-related status of gray whales.
- Issue published online: 26 AUG 2006
- Article first published online: 26 AUG 2006
- Received: 6 January 1999 Accepted: 16 March 1999
- western gray whale;
- Eschrichtius robustus;
- Okhotsk Sea;
- occurrence patterns;
- site fidelity
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 reidentified 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.