Cascadia stranding response

As a part of the Northwest Marine Mammal Stranding Network, Cascadia is active in responding to strandings of cetaceans and pinnipeds. Primary long-term interests have included:

• Incidence and causes of death of large whales in the Pacific Northwest. This has included examination of gray whales, the most frequent large whale to strand in our waters (link to Cascadia's overall gray whale research).
• Trends in contaminants in harbor seals and other marine mammals. This has included tracking changes in levels of PCBs and pesticides using stranded non-starved neonate harbor seals as an indicator (link to list of reports on contaminant trends)
• Status and population structure of harbor porpoise including use of contaminants as an indicator of different populations along the US West Coast. An Unusual Mortality Event (UME) was recently declared for this species due to unusually high number of strandings in 2006.

Cascadia collaborates with National Marine Fisheries Service and the Washington Department of Fish and Wildlife in stranding response and examination of stranded animals. Support for stranding response and research has come through the Prescott Marine Mammal Rescue and Assistance Grants Program.

Information on specific recent whale strandings in Washington

• Killer whale dorsal fin found at Twin Harbors State Park 22 May 2007

• Examination of dead gray whale from Johnson Pt., 1 May 2007

• Humpback whale examination – 6 October 2006

• Minke whale stranding in south Puget Sound, 24 August 2006

• Examination of fin whale conducted 16 May 2006, Lummi Nation

• Gray whale stranding near Steilacoom in July 2005
• Report from examination of Bremerton gray whale stranding on 5 May 2005
• Stranding and sighting update on 28 April 2005
• Gray whale stranding Whidbey Is. April 2005

Pinniped stranding response

Cascadia has responded to 182 pinniped strandings from 2003 to 2006 (Table 1) and assisted in another 52 examinations of pinnipeds conducted by WDFW (Table 2) in Washington State involving five species of pinnipeds. Both gross examinations of animals at necropsy combined with histological examination of tissues (conducted by Dr. Stephen Raverty of the Animal Health Center, BC) revealed a variety of causes of death of pinnipeds. Primary causes of death of pinnipeds included infectious agents, malnutrition/starvation, and accident/trauma.

Active searchers were conducted for stranded neonate harbor seals at several harbor seal haul out areas to collect tissues of non-starved neonates to monitor trends in contaminants in this indicator group. An exceptionally high rate of mortality of harbor seal neonates was found at this site in 2005 where in 5 visits in 2005, 110 dead pups were recovered from this site. Detailed examinations were conducted in collaboration with the WDFW and also the Animal Health Center in British Columbia but these did not reveal any consistent cause of death in the 2005 animals.

A variety of tissues have been submitted and are in the process of contaminant analysis. The focus will be analysis of non-starved harbor seal neonates that will provide data on long-term trends in contaminant concentrations going back to the early 1970s (Calambokidis et al. 1991, 1999, 2005). Longest trends will be available for PCBs and DDT compounds which were tested for in all analyses. Recent analyses completed has also included tests of metals and trace elements in liver tissues of harbor seal pups from Gertrude Islands in 2004 and 2006 and Smith Island in 2005.

Table 1. Pinniped stranding response by Cascadia Research, 2003-2006.

Table 2. Breakdown by species and year for necropsies or responses where WDFW was lead by Cascadia provided assistance, 2003-2006.

Ship strikes of large whales

Abstract of manuscript submitted to Journal of the Marine Biological Association of the United Kingdom and presentation submitted to the 2007 Biennial Conference on the Biology of Marine Mammals in Cape Town, South Africa:

Ship strikes of large whales off Washington State, USA: an analysis using stranding records from 1980-2006

Douglas, Annie B.¹; Calambokidis, John ¹; Raverty, Stephen²; Jeffries, Steven J.³; Lambourn, Dyanna M.³; Norman, Stephanie A.⁴

(1) Cascadia Research Collective 218 ½ W Fourth Ave., Olympia, WA 98506 USA

(2) Animal Health Center, British Columbia Ministry of Agriculture and Food, 1767 Angus Campbell Road, Abbotsford, BC V3G 2M3 Canada

(3) Washington Department of Fish and Wildlife, 7801 Phillips Road SW, Lakewood, WA, 98498, USA

(4) Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle, WA 98195 USA

Worldwide, fin whales have been recognized as the species most frequently affected by ship strikes, but as more research is undertaken, regional differences in species affected are becoming apparent. In the interest of evaluating ship-strikes off Washington State, an area where several species seasonally travel and feed within major shipping channels, we examined large whale stranding records from 1980-2006. Of 130 whale strandings, 19 (15%), representing seven species, had evidence of ship strikes. There was a significant increase in the number of ship-struck whales over this period, although the annual proportion of whales with evidence of ship strikes, compared to the total number of strandings, did not change significantly over time. Fin whales had the highest incidence of ship strikes (all seven strandings of this species), mostly consisting of immature animals with all but one occurring since 2002. Six gray whales suffered “possible antemortem ship strikes”; however, this represented only 6% of gray whale strandings since this species accounted for 80% of large whale strandings; indicating that the number of ship strikes likely reflects their seasonal abundance, rather than a high vulnerability to ship strikes. We recorded one of three stranded humpbacks as ship struck, despite concentrations of humpbacks feeding within shipping lanes. Other species documented with ship-strike injuries were blue (2/2), sei (1/1), sperm (1/3) and Baird’s beaked whale (1/1). We believe the dramatic difference in occurrence of ship-struck whales by species results from a combination of a species’ abundance, vulnerability to ship strikes, and the likelihood of a struck whale being caught on a ship’s bow and brought into waters where it may be discovered. Given the variability in species affected by ship strikes worldwide, awareness and solutions to this type of mortality will require consideration of differences in species vulnerability by region.