By Carol Keiper, M.Sc. Marine Ecologist,
Oikonos Ecosystem Knowledge
Ship strikes of endangered blue and humpback whales has become an issue of great concern off California with recent events in the San Francisco area. Three endangered whales died from ship strike injuries during July, September and October 2010, including an 84 ft. pregnant female blue whale that washed up with her 17 ft. long fetus on Bean Hollow State Beach in San Mateo County.
Dead whale strandings along the coast related to ship strikes may represent only a small portion of true ship strike mortality; most cetacean bodies are never recovered because they either sink or do not come ashore (John Calambokidis, personal communication). Actual deaths from ship strikes may be higher than beach strandings would indicate.
Blue and humpback whales migrate thousands of miles to critical foraging areas along the west coast of California, Oregon, and Washington that include the waters within the Gulf of the Farallones, Cordell Bank, Monterey Bay, Olympic Coast and Channel Islands National Marine Sanctuaries. The identification of major feeding areas for these whales, overlapping with areas of high ship densities, has become a priority for conservation planning.
My colleagues and I received funding from Pacific Life Foundation to examine the extent to which blue and humpback whales feed and transit in designated shipping lanes for San Francisco Bay in order to identify primary areas of overlap and assess potential risks. Vessel traffic data during August through October for 2009-2010 were selected because historically, both blue and humpback whales tend to be more abundant during these months in the study area when their preferred prey (krill and small schooling fish) are most abundant.
During August through October 2009, the total number of vessels was 2,550, and in 2010, the total number of vessels was 2,443. The majority of vessels were cargo ships (52%), tankers (24%), and fewer trips made by "other" smaller vessels, such as passenger, pilot, search and rescue, port tender, military ops, underwater ops, law enforcement, sailing, pleasure, fishing, unidentified (14%) and towing or tugs (10%).
To investigate the relative risk on endangered blue and humpback whales, an integrated database was created with historical observation whale sighting data sets from several systematic survey programs during 1980-2010: Cascadia Research data from 1991-2010, and California Department of Fish and Game Office of Spill Prevention and Response flight data from 2001-2008. Opportunistic whale watching data collected on trips to the Farallon Islands in the Gulf of the Farallones National Marine Sanctuary was also used in our analysis.
Using GIS (Geographic Information System) mapping analyses, we identified a clear area of overlap of humpback and blue whales during their seasonal high use feeding in August-October and vessel traffic densities in the San Francisco shipping lanes. We discovered the highest risk areas were found in the vessel traffic lanes of the western approaches, south of the Farallon Islands and within the Gulf of the Farallones National Marine Sanctuary. The increase in the numbers of vessels using the western approach lanes to San Francisco is due to the mandatory low sulfur fuel-switching required 24 miles out in the regulated California waters.
Our greatest concern of ship strikes is with the Eastern North Pacific stock of blue whales that does not appear to be growing. Estimates are only 2,842 individuals, whereas the humpback whale population appears to be more robust with a best estimate of 18,000-20,000 in the entire Pacific Basin, including 2,042 for the CA and OR regions. Regardless of the numbers of blue and humpback whales, they are both endangered species and require thoughtful conservation actions to mitigate this known threat.
We found GIS mapping to be a useful tool to identifying critical whale feeding habitat and providing details on threats from ship traffic. Results of our research will continue to be presented to resource managers and the shipping industry, so that solutions may be found to reduce the negative interaction between vessel traffic and whales in the Cordell Bank and Gulf of the Farallones National Marine Sanctuary Joint Working Group on Vessel Traffic.
Generating awareness about the plight of great whales along the California coast has created new projects and ideas for their protection. Efforts include continuous monitoring and collecting data from whale-watching cruises, training captains on fishing and whale watching vessels, along with naturalists and/or volunteers, to become "citizen scientists" who can collect opportunistic data. This will fulfill an important data gap and contribute to the protection of the great whales from the increase in vessel traffic.
Future research on whale behavior within and near shipping lanes is more important than ever. Much of this work is based on the pioneering studies of the behavior of blue whales off Southern California by John Calambokidis and Cascadia Research Collective.
More questions have emerged from this work:
- How do blue and humpback whales react to vessels in and near shipping lanes off San Francisco?
- Will feeding or transiting whales behave differently to vessels?
- Does vessel size or sound influence how a whale might react?
We know blue and humpback whales will remain in areas of high prey biomass for days or weeks. One of the important foraging areas is the shelf break (edge of the continental shelf) and slope. We hope to use this information to create a predictive scientific model of presence and absence of the whales in critical foraging areas to inform vessel traffic advisories.
Thus far, our primary recommendation to the United States Coast Guard for the Port Access Route Study (PARS) project was to extend the western approach shipping lanes beyond the edge of the continental shelf. This would potentially result in ships approaching the lanes outside of the higher whale density areas and then crossing these areas in a shorter segment of the shipping lanes. It was enlightening to read the latest PARS recommendations that included extending these western approach shipping lanes to the 100 fathom isobath (depth contour). By working cooperatively with scientists, managers and the Coast Guard, we hope to find best, feasible long-term solutions to this conservation issue.
Oikonos Ecosystem Knowledge is a non-profit 501(c)(3) organization working locally and internationally to increase ecosystem knowledge through science, art, technology, education, and applied conservation. Results of this project can be viewed on the Oikonos website including maps of blue and humpback whale density distribution patterns, opportunistic whale sightings from whale watching trips, and maps that show shipping traffic use and relative risk areas.
How can you help with this threat to endangered whales? Spread the awareness in schools, libraries, and public forums that whales need our protection.
For more information on our project and ways you can help see: Oikonos Ocean Conservation: Large Whales and Shipping Lanes
Important New Marine Mammal Guide: S.G. Allen, J. Mortenson, and S.Webb. 2011. Field Guide to Marine Mammals of the Pacific Coast. California Natural History Guide Series No. 100, University of California Press.