The National Marine Fisheries Service today reported a stable trend in the number of endangered Steller sea lions (SSLs) in Alaska. While concerns remain about numbers in the Central and Western Aleutians, the stable trend overall was welcome news said Dave Benton, executive director of the Marine Conservation Alliance. “It’s noteworthy that the SSL counts in the Eastern Aleutians, where most commercial fishing activity in the Bering Sea takes place, have increased by seven percent since 2004 and is the only region where western SSL populations have steadily increased since 2000.”
The adult and juvenile Steller sea lion population assessment conducted by the National Marine Fisheries Service earlier this year is the first complete census since 2004. The results were released today during meetings in Seattle on Alaska fisheries stock assessments and will be used by the agency to determine whether current management measures are adequately protecting SSL populations.
Concerns remain about the Central and Western Aleutian Islands where SSL counts declined by 16 percent and 30 percent respectively despite stringent restrictions on the commercial fishing fleet in the area for more than eight years. “The fact that SSL counts continue to decline in the Central and Western Aleutians despite no‐fishing zones around rookeries and haul‐outs, and accounting for forage needs in fishery management plans, indicates that other causal factors are involved in the decline,” Benton said. “We need continued scientific research to determine those factors and help rebuild these stocks.”
Steller sea lion counts in Alaska dropped sharply in the late 1980s prompting the species’ listing as threatened under the Endangered Species Act in 1990. In 1997, a distinct “western” stock of SSLs was identified in Prince William Sound the Aleutian Islands and extending to Russia, and was declared endangered.
Despite the decline in the Central and Western Aleutians the overall western SSL population has been stable since the agency completed its last biological opinion. Overall, SSL counts in Central and Western Gulf of Alaska increased 10 percent and 6 percent respectively since 2004. The most dramatic increase documented this year was in Prince William Sound, where the count increased by 1,350 animals from the previous year.
Considerable debate remains about possible causes for the decline and factors affecting rebuilding. While some have pointed to commercial fishing activity in the Bering Sea reducing the availability of feed, marine mammal researcher Dr. Ian Boyd of the University of St. Andrews in Scotland told the North Pacific Fishery Management Council, “There’s really very little evidence to support the idea that there’s been nutritional stress in this population as a causal factor in the population dynamics.”
Dr. Jason Matthiopoulos, another researcher at the University of St. Andrews’ Sea Mammal Research Unit, added, “Walleye pollock and Pacific cod … have a relatively low‐energy content. Regulation of these fisheries is less important for Steller sea lion conservation than controlling catches of energy‐rich … species like herring and eulachon (candlefish).”
Other scientists point to a climate shift known as the Pacific inter‐Decadal Oscillation and predation by killer whales as contributing factors. Researchers in British Columbia (Guenette, et al.) suggested that “killer whale predation contributed to the decline of sea lions in the central and western Aleutians, but that predation was not the primary cause of the population decline. However, predation could have become a significant source of mortality during the 1990s when sea lion numbers were much lower.”
The Steller Sea Lion Recovery Plan, finalized by the agency last year, recognized multiple causes for the decline of the population including shootings which are now illegal. Impediments to full recovery remain speculative, but the recovery plan identified climate change, competition for prey with fishermen and killer whale predation as contributing factors. The North Pacific Council has imposed costly restrictions on the commercial fishing industry to protect the Steller sea lions. The effectiveness of those restrictions will be evaluated next year when the agency releases a new Biological Opinion
MCA supports continued scientific research to conserve and rebuild SSL populations and urges the incoming Obama Administration and Congress to maintain that commitment despite the current economic challenges.
Based in Juneau, the Marine Conservation Alliance is a coalition of seafood processors, fishermen, coastal communities and support industries involved in the Bering Sea and Gulf of Alaska groundfish and crab fisheries. The MCA promotes science‐based conservation measures to ensure sustainable fisheries in Alaska. For more information, visit www.marineconservationalliance.org.
- Donna Parker, MCA Spokesperson and SSL Recovery Plan Team Member 206-295-4766
- Dave Benton, executive director, Marine Conservation Alliance, 907-321-0499
- Dr. Doug DeMaster, Science and Research Director, Alaska Fishery Science Center, 206-526-4047
- Andrew Trites, Director, North Pacific Universities Marine Mammal Research Consortium, 604-822-8182
Matthiopoulos, J; et al, 2008 – Getting beneath the surface of marine mammal – fisheries competition, Mammal Review, 38, 167-188.
Guénette, S., et al., 2007, Ecosystem models of the Aleutian Islands and southeast Alaska show that Steller sea lions are impacted by Killer Whale predation when sea lion numbers are low, in Proceedings of the Fourth Glacier Bay Science Symposium, October 26–28, 2004: U.S. Geological Survey Scientific Investigations Report 2007-5047, p. 150–154.