The Seattle Aquarium has hosted its biennial Sea Otter Conservation Workshop since 1999. What began as an intimate gathering of about 50 biologists has grown into an international event with over 120 attendees from locations including the U.S., Canada, Europe, Japan and Russia.
The three-day meeting brings together sea otter biologists, ecologist, experts in animal care, veterinarians, state and federal permitting agents, advocacy groups and others interested in sea otter conservation, with a goal of sharing pertinent scientific information and discussing what needs to be studied or what action steps are necessary to effectively conserve sea otters in the wild and in zoos and aquariums.
Topics covered include: population trends; ecology; food webs; genetics; updates on the status of sea otters living at zoos and aquariums; animal care and training; physiology; veterinary cases; economic impacts; diet diversity; population carrying capacities; reintroductions of sea otters back to portions of their historic range; and strategies for placing non- releasable rehabilitated sea otters in zoos and aquariums; and more.
This year’s workshop, the event’s 10th anniversary, was held March 17–19, and featured Seattle Aquarium staff members presenting on some of research being led here:
Diets developed for sea otters living in zoos and aquariums
We sent a survey to 24 facilities around the world that exhibit sea otters to document the diets of 62 individual sea otters. Data gathered included the specific types of seafood offered, where that seafood was harvested, how much each sea otter ate daily, and how much of the seafood was offered whole (still in the shell) versus prepared (shelled or chopped into smaller pieces).
Hormones extracted from sea otter feces
We’ve been collecting fecal samples to extract fecal hormones to determine reproductive activity in our sea otters for over 20 years. We’ve also been looking at routine stress hormones in the feces and wondering what might make stress hormones rise above baseline. Preliminary analysis is pointing toward brief rises in stress hormones when the animals are receiving a veterinarian exam, in proximity to construction projects and giving birth.
Toxins in seafood and in sea otter feces
We’ve begun measuring persistent organic pollutants in our animals’ food and feces. Currently we can assay for PBDEs (flame retardants) and DDT/DDE, a legacy, persistent pesticide. We measure levels in the food offered and what comes out in their feces. The levels in the food are higher than in the feces, which means there is a potential that some of the chemicals are absorbed in the animals’ bodies. How much is absorbed and how this affects their health is still unknown. The Aquarium’s sea otters are fed sustainably harvested, restaurant-grade seafood—the same seafood eaten by humans, which means people may be absorbing similar levels of chemicals as well.
The Washington state sea otter census
The Aquarium has participated in the annual Washington sea otter census since 2001. Our role is to count sea otters we see from the ground to validate the counts of sea otters in high-resolution photographs taken from a plane. In 2016, over 1,800 sea otters were counted, representing a long-term population growth rate of approximately ten percent per year.
Wild Washington sea otter diet
Since 2010, the Seattle Aquarium has been documenting the types of seafood eaten by wild sea otters off the Washington coast by using high-powered spotting scopes to observe the animals foraging in the nearshore habitat. This information can be compared to data we have from sea otters living in zoos and aquariums and gives us an idea of the health of the sea otters and the health and productivity of the nearshore areas.
Range-wide genetic diversity
The Seattle Aquarium has been studying genetic diversity in wild sea otters for 18 years. Recently we acquired a new data set of genetic material from across the sea otters’ current and historic range. We compared this to earlier data sets and found that most populations of sea otters have had an increase in genetic diversity. The greatest increase was found in areas where sea otters had gone extinct and then, years later, groups of animals were relocated back into the area. If sea otters from two different groups were relocated, this caused a mixing of genes—which increases genetic diversity. The greatest diversity increase, almost 30 percent, was found in Washington state, where sea otters have been known to mix with populations to the north along Vancouver Island.
Subspecies definitions using genetic data
Sea otters are divided into three distinct subspecies: the common or Asian sea otter, in Japan and Russia; the northern sea otter, found in much of Alaska, British Columbia and Washington; and the southern sea otter, which lives in central California near Monterey Bay. The Seattle Aquarium is using both nuclear and mitochondrial DNA to re-evaluate the subspecies of sea otters. The genetic differences found support these three subspecies but also may suggest that another potentially genetically distinct subspecies lives in Alaska’s Prince William Sound. More research is needed.
The rehabilitation of Rialto
Sea otter studbook
The Association of Zoos and Aquariums (AZA) produces regional studbooks which document the pedigree and entire demographic history of each individual in a population. Studbooks are invaluable tools that track and manage animals cared for in AZA-accredited institutions. The Seattle Aquarium maintains the studbook for all 53 of the sea otters currently housed in zoos and aquariums in North America.
Interested in learning more about sea otters? Come visit us at the Seattle Aquarium—and check out our sea otter fact sheet!