Biologists Survey Blue Whales by Sailboat in Gulf of Farallones

This summer, concentrations of blue whales were higher than ever recorded in the waters off Central California. Biologists Beth Mathews and Jim Taggart volunteered to help document the unusual abundance.

© Beth Ann Mathews

August 2020 - In recent decades, humpback and blue whales have become more abundant in the waters off Central California. But this summer, concentrations of blue whales were higher than ever recorded. Point Blue Conservation Science biologists on the Farallon Islands reported sightings of up to 47 blue whales in an hour. Point Reyes National Seashore Wildlife Ecologist Dave Press saw blue whales everywhere while visiting the Great Beach.

Cascadia Research Collective (CRC) has done long-term research on humpback and blue whales along the US West Coast and elsewhere for decades. This summer, their regular survey coverage was limited because of the coronavirus. Still, CRC Senior Research Biologist John Calambokidis wanted to document the unusual abundance of blue whales. He put out a call for help to collaborators on his research permit. Biologists Beth Mathews and Jim Taggart volunteered. In July, they set out on their sailboat to conduct photo-identification surveys in the waters off Point Reyes, out to Cordell Bank National Marine Sanctuary.

CRC has conducted annual photo-identification surveys of whales since 1986. Their catalog includes photos of over 2,500 individuals. Humpback whale flukes, and blue whale flanks and dorsal fins all have unique pigment patterns. These allow researchers to identify individuals and estimate population sizes and trends (NOAA). CRC's research objectives include:

• estimating humpback and blue whale abundance off Oregon, Washington, and California;
• determining trends in these populations;
• identifying critical feeding habitats that need protection; and
• monitoring potential human-caused threats to these populations (e.g., ship strikes and sonar impacts).

These data were crucial to informing shipping lane locations into and out of San Francisco Bay. Well-placed lanes avoid predictable whale feeding areas to reduce the chances of ship strikes.

Blue whales probably did so well along the coast this season because 2020 was an especially good year for krill, their primary food.

© Beth Ann Mathews

Though this was the first time Beth and Jim have searched for blue whales, they are not new to marine mammal research. Beth has studied humpback and gray whales, and focused on harbor seal and Steller sea lion research for many years in Glacier Bay National Park & Preserve. Jim studied walruses and other species in the Arctic, and did research on halibut and Alaskan crab species for USGS in Glacier Bay. The couple now live in the Bay Area. They once sailed Resilience, the 42 ft sailboat they’ve owned for nearly 30 years, from Alaska to Baja, Mexico with their son. They welcomed the opportunity to support CRC’s long-term whale research in their backyard.

The suggested reason for this unprecedented concentration of blue whales? 2020 was an especially good year for krill, their primary food. The krill did well because of particularly strong spring winds that promote nutrient upwelling, the basis of the marine food web.

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