2015 Subtidal Surveys

NOAA Subtidal surveys assess sea otter effects on nearshore habitats
Liam Antrim, Olympic Coast National Marine Sanctuary
Greg Williams, NOAA Fisheries' Northwest Fisheries Science Center

Video thumbnail to YouTube showing sea otter habitats.

Two teams of NOAA scientists joined forces during August 2015 to conduct subtidal dive surveys in Olympic Coast National Marine Sanctuary. Survey transects replicated work completed in decades past to evaluate changes associated with re-introduction and expansion of the sea otter population along the outer coast of Washington.

This research is a collaboration between NOAA's Olympic Coast National Marine Sanctuary and NOAA Fisheries' Northwest Fisheries Science Center, who provided staff time and expertise from their scientific dive team.

Divers returned to locations visited in 1987, 1995 and 1999 to evaluate community changes associated with growing sea otter numbers, expansion of their range and changes in availability of their food sources, or prey. Long-term monitoring is essential to understand the health of marine populations as well as changes that occur in response to predation by sea otters and other pressures on marine resources.

Sea otters are voracious feeders, eating more than 12 pounds of seafood (25% or more of their body weight) daily. Washington sea otters' diets consist of a variety of invertebrate species, including crabs, mussels, clams, scallops, abalone, sea urchins, octopus, squid, snails, and sea stars. They can dive to over 100 feet in search of food. As the number of sea otters grows and their consumption of prey increases, scientists expect to see a corresponding shift in marine communities, and potentially in kelp bed habitats. Data gathered through the subtidal SCUBA surveys will provide important information about the condition of sanctuary subtidal communities, and Pacific Northwest coastal ecosystems in general.

The northern sea otter (Enhydra lutris kenyoni) was hunted to local extinction in the early 1900s as a result of the fur trade. To reintroduce the species to the outer coast of Washington, 59 sea otters from Alaska were released near La Push and Point Greenville between 1969 and 1970. This sea otter population has grown to approximately 1,600 individuals (based on the 2014 census), and northern sea otters now occupy a primary range north of Cape Elizabeth to Tatoosh Island, with some venturing into the Strait of Juan de Fuca and Salish Sea. Sea otters are a well-documented keystone species, with feeding habits that have a significant influence on nearshore marine communities.

For information contact Liam Antrim.

Contact for page content: Liam Antrim