(CN) - The National Marine Fisheries Service can limit commercial fishing in the Northern Pacific to protect a dwindling population of sea lions, the 9th Circuit ruled Tuesday.
The agency proposed in 2010 to close mackerel and cod fishing in the Aleutian Islands region, and to limit fishing in other areas around the Bering Sea and the Gulf of Alaska, after discovering that two subpopulations of endangered Steller sea lions had experienced sharp declines in population from "nutritional stress," allegedly caused by commercial fishing. Four other groups meanwhile had seen an increase in population.
Fearing economic repercussions, Alaska and several fishing companies challenged the limits, and Greenpeace and Oceana joined the federal action as defendants.
Alaska and the fishing companies argued that the National Marine Fisheries Service had violated the Endangered Species Act when it based the restrictions on a subpopulation instead of all of the region's sea lions. They also claimed that the agency had improperly measured the alleged decline, and had failed to show a clear relation between fishing and the relative health of the animals.
U.S. District Judge Timothy Burgess in Anchorage found no violation in the limits and ruled that the agency did not have to show such a "definitive causal connection" between fishery activity and the sea lion's decline.
A three-judge appellate panel unanimously affirmed on Tuesday.
"We have consistently held that the ESA permits agencies to consider the impact of actions on sub-populations, as long as such impact would affect the population as a whole," Judge Mary Schroeder for the Seattle court, abbreviating Endangered Species Act. "We recognized that trends with regard to a subset of a species can provide important indicators about the health of the entire species."
The panel also would not attribute the decline to killer whales since orcas enjoy eating sea lions.
"Citing a number of studies regarding killer whales, the agency specifically looked to the long-term historical trends and concluded that the studies 'argue against the hypothesis that killer whale predation alone was responsible for the decline' in population," the ruling states.
The Steller, or northern, sea lion is the largest of the "eared seals." Males can grow to be 11 feet long and 2,500 pounds. The National Marine Fisheries Service estimates that there are about 39,000 to 45,000 Steller sea lions in the western United States, and some 44,500 to 48,000 in the east.