That’s A Wrap: The 2005 Field Season in Review

Cruising for Stellers
Scientists from UBC, the Alaska Department of Fish & Game (ADF&G), and Fisheries and Oceans Canada (DFO) embarked on several cruises this summer along B.C.’s north coast and through Southeast Alaska. Their purpose was twofold: to collect hundreds of fecal (scat) specimens from haul-out and rookery sites, and to tally sightings of branded sea lions.

Put simply, scat samples reveal what a sea lion population is eating. Scientists are particularly interested in comparing the diet of the healthy and growing populations of Steller sea lions in BC and Southeast Alaska – with the diet of their declining Western Alaska counterparts. These field samples paint a dietary picture for each population that is supported by baseline data from the captive Steller sea lion research program at the Vancouver Aquarium Marine Science Centre.

Approximately 500 of these samples will fuel research to develop a new method of identifying and quantifying prey species by DNA analysis. Principal Investigator, Dr. Dom Tollit, in a collaboration with the DFO, the National Marine Fisheries Service (NMFS) and University of Alaska Fairbanks (UAF), hope this approach will enable researchers to identify not only which prey species are in a scat sample, but also, for key species like salmon, their particular stock or population. The project's goal is to synthesize DNA results with information from prey hard remains to determine the amounts ingested.

The second purpose of the cruises, brand resighting, is akin to trainspotting: researchers observe and record unique “license plate” numbers that are branded to the side of individual sea lions as part of research program led by ADF&G, NMFS, and the Oregon Department of Fish and Wildlife. By recording when and where a branded animal is resighted, scientists can estimate survival rates, determine which component of a population is at greatest risk, and follow the movements of sea lion pups as they age and mature.

The Island Life The 2005 field season brought both a beginning and an end to two long-term field projects based in Alaska. Michelle Marcotte’s “Steller Watch” program wrapped up in Southeast Alaska after 13 months of continuous observations at a haul-out on South West Brothers Island. Marcotte is currently preparing her Masters thesis, which examines when sea lions wean and determines the seasonal and daily activity levels and haulout patterns of the island’s resident Steller sea lions.

Further north in Alaska in the Bering Sea, Masters student Pamela Lestenkof began a study of northern fur seals on the Pribilof Islands, with the assistance of researchers from the National Marine Fisheries Service. Lestenkof’s interest in the fine-scale feeding behavior of fur seals is more than a passing interest: as an Aleut, born and raised among the indigenous people of the Aleutian Islands, her study of fur seal foraging relative to commercial fishing activity in the eastern Bering Sea may have implications for fisheries management.

Tales of Transients
Elsewhere in the marine mammal world, Volker Deecke continued his research on the acoustic behaviour of transient killer whales in Southeast Alaska. Wary of the acute hearing of their marine mammal prey, transients usually hunt silently but vocalize loudly after making a kill. Deecke employs an array of underwater microphones (hydrophones) to record the direction and intensity of these post-kill vocalizations. He is working to set up permanent underwater listening stations near sea lion rookeries and haul-outs in order to study the impact of transients on sea lion mortality.

The UBC field team also reported several unusual instances of killer whale predation. On July 21, field researchers Andrea Coombs and Rod McVicar observed a group of 17-20 visiting Southeast Alaska transients off the west coast of the Queen Charlotte Islands. They reported at least four individual killer whales actively harassing a five-foot long squid for several minutes before losing interest and moving on. In general, killer whales feed on a wide range of prey, including squid - this unidentified squid got lucky and swam away, but the bizarre encounter between these animals is the first known interaction of its kind.

Meanwhile, in western Alaska, Dr. Lance Barrett-Lennard (Vancouver Aquarium Marine Science Centre) and Craig Matkin (North Gulf Oceanic Society) continued their study of transient killer whale predation on gray whales at False Pass in collaboration with the Alaska SeaLife Center. False Pass is an extremely narrow passage at the tip of the Alaskan peninsula, where transients hunt in unusually large and noisy groups.

Each spring, as hundreds of northbound gray whales migrate through False Pass, groups of 20-60 vocally active transients hunt down the juvenile gray whales and feed on their carcasses. Because the gray whales are effectively “sitting ducks,” the killer whales have no need for their typical silent hunting strategy. Astonishingly, none of these transients were familiar to Barrett-Lennard and Matkin when they first observed this behavior in 2003; the pair has since identified and added 110 False Pass transients to the killer whale catalogue.

Despite poor weather conditions and logistical challenges, the research team maintained a strong presence in the field this summer. Armed with a year’s worth of collected data and specimens, the researchers will answer some important questions over the coming months – but will likely ask many more. In the process, they will find even more reasons to be out in the field next year.

14 November 2005