Under Federal Law (Endangered Species Act and Marine Mammal Protection Act), NOAA Fisheries is mandated to monitor the two distinct population segments of Steller sea lions, the Eastern and Western populations.
The Eastern Population ranges east of 144°W longitudinal line (just east of Prince William Sound, Alaska) through southeast Alaska, Canada, and the west coast of the contiguous United States.
Generalized distribution (crosshatched area) of Steller sea lions in the North Pacific and major U.S. haulouts and rookeries (50 CFR 226.202, August 27, 1993), as well as active Asian and Canadian (British Columbia) haulouts and rookeries (points: Burkanov and Loughlin 2005; S. Majewski, Fisheries and Oceans Canada, pers. comm.). Black dashed line (144°W) indicates stock boundary (Loughlin 1997) and solid black line delineates U.S. Exclusive Economic Zone.
The Western Population ranges west from the 144°W longitudinal line through the Gulf of Alaska, Aleutian Islands, and beyond the U.S. border through Russia and Japan. This population has been on the Endangered Species list since 1997.
Continued research on abundance, movements and vital rates, and diet and foraging behavior helps us understand the role of Steller sea lions in the marine ecosystem and inform management decisions for the conservation of this important species.
Estimating Steller Sea Lion Abundance
Estimating the abundance, or number of Steller sea lions in the populations, can be difficult for such a wide-ranging species. Each year, during the summer breeding season, we conduct aerial, ship, and land-based surveys to collect counts of sea lions on land. We use these data in computer models to create stock assessments.
Steller sea lion researchers surveying rookery.
Studying Steller Sea Lion Movements and Vital Rates: How They Live, Breed, and Grow
We permanently mark a very small portion of sea lions so that we may monitor these individuals throughout their lifetime. We use this information to learn how long sea lions live, how often females give birth to young (or “pups”), and if sea lions move from their natal region, or area they were born. This information, along with other studies investigating health and disease, help us understand the overall condition of sea lions in different regions across the range of the species.
You can help biologists look for these marked animals on Steller Watch!
Steller Sea Lion Diet and Foraging Behavior
There are many ways we can research Steller sea lion diet and foraging behavior—where sea lions go while at-sea, and how deep they dive, to catch their food, or “prey.” One of the most common ways is collect their scat, or feces, on land. We can use the hard parts (like fish bones) left behind to identify their prey and size of prey. We also use satellite transmitters, or tags, that are glued onto a small number of individuals to track their movements and dive characteristics to understand important foraging areas.
Steller sea lion with a satellite transmitter glued to its head. This “tag” technology allows us to track sea lion movements over short periods of time.
Reports
- Coordination of Proposed Steller Sea Lion Field Research Activities in Alaska, 2007
- Steller Sea Lion Field Research Coordination 2008 Meeting Report
- Minutes of 2009 Steller Sea Lion Research Coordination Workshops Held in Anchorage, Alaska and Seattle, Washington
- Minutes of 2010 Steller Sea Lion Research Coordination Workshop Held in Anchorage, Alaska
- 2011 Steller Sea Lion Research Coordination Workshop Report
- Aerial Survey of Steller Sea Lions in Alaska, June-July 2009 and Update on the Status of the Western Stock in Alaska
- Surveys of Steller Sea Lions in Alaska, June-July 2010
- Results of Steller Sea Lion Surveys in Alaska, June-July 2011
- Results of Steller Sea Lion Surveys in Aleutian Islands, Alaska, June 2012
- Results of Steller Sea Lion Surveys in Alaska, June-July 2013
- Results of Steller Sea Lion Surveys in Alaska, June-July 2014
- Results of Steller Sea Lion Surveys in Alaska, June-July 2015
- Results of Steller Sea Lion Surveys in Alaska, June-July 2016
- Results of Steller Sea Lion Surveys in Alaska, June-July 2017
- Results of Steller Sea Lion Surveys in Alaska, June-July 2018
Additional Resources
- Steller Sea Lion Regional Management Information
- Programmatic Environmental Impact Statement for Steller Sea Lion and Northern Fur Seal
- Steller Sea Lion Pup Count Database
- Steller Sea Lion Non-Pup Count Database
- Steller Sea Lion Brand Database
- Steller Sea Lion Haulout and Rookery Locations
- Steller Sea Lion 2016 Field Season Research Map
- Steller Sea Lion Databases
- Co-Management of Marine Mammals in Alaska
