Gray whales in Washington State: report on research in 1996
Calambokidis, J. and J. Quan. 1997. Gray whales in Washington State: report on research in 1996. Final report to National Marine Mammal Laboratory, Seattle, Washington. 30pp.
This report summarizes research conducted by Cascadia Research in collaboration with the National Marine Mammal Laboratory during the 1996 field season. Cascadia Research has been conducting research on gray whales in Washington waters using photographic identification of individual animals since the mid-1980s (Calambokidis et al. 1994) with the goals of determining the number of whales using Washington waters, preferred areas for feeding, seasonality of use, and degree to which animals return year to year.
Fifty boat surveys were conducted by biologists with Cascadia to observe gray whales between 15 March and 6 October 1996 totaling 243 hours of observation and 1,486 nmi of coverage. These included dedicated boats surveys conducted using a rigid-hulled inflatable and effort aboard whalewatch trips. The heaviest effort was in Grays Harbor, the western the Strait of Juan de Fuca, the northern Washington outer coast, and in the northern Puget Sound area. Data were also contributed by biologists at the National Marine Mammal Laboratory who provided identification photographs of gray whales made on an additional 13 days (between 13 June and 26 September) from surveys on the northern outer coast and the western Strait of Juan de Fuca. Gray whales were individually identified using photographs of the natural markings on the right and left sides. Comparisons of identified individuals were made to Cascadia’s catalog of over 100 gray whales seen in previous years off Washington as well as catalogs of identification photographs taken by collaborating researchers in British Columbia. A total of 112 sighting reports of gray whales were received by Cascadia Research and the Whale Museum in 1996.
A total of 47 different gray whales were identified on 1996 in the study. A high proportion of the whales identified in three regions (northern Washington coast, Strait of Juan de Fuca, and southern Vancouver Island) were seen multiple times (73-79% by region) and had been identified in a previous year (64-82%). Gray whales identified near Grays Harbor early in the season were less likely to have been seen multiple times (52%) or a previous year (26%). Because most of these whales were identified in the migratory corridor during the migration (26-52%) when we would expect to be seeing migratory whales, this lower proportion of ‘resident’ whales was surprisingly high. Gray whales were frequently identified in multiple regions indicating movement patterns. Comparison of photographic catalogs with researchers working in British Columbia revealed that many of the whales that feed along the Washington coast through the summer range along the British Columbia coast to areas north of Vancouver Island.
Conclusions of the research conducted through 1996 include:
- Gray whale use of southern and central Puget Sound is highly variable; few animals came into these waters in 1996. Previous research has shown whales that have been identified in these waters have never been resighted across years and have not been seen in other regions.
- A consistent group of individual gray whales had returned annually to the waters around Whidbey Island but the duration of their stay has become shorter. In 1996 we were not successful in finding these animals in this or any other region.
- A consistent group of individual whales feed each summer along the Washington outer coast and Strait of Juan de Fuca and range north past Vancouver Island. Some of these animals have returned over a 20 year period.