Alaska Sea Grant

Sea Otter Story Part 3

Sea urchins feed on kelp

After his boat surveys in the 1990s, Jim Estes worked with the biologists and managers of the Alaska Maritime National Wildlife Refuge to try to understand what was causing the sea otter population in the Aleutian Islands to once again be heading toward extinction.

It was their responsibility to find out the cause of the decline, which was the most rapid die-off of a marine mammal ever recorded. The cause of the decline was puzzling. Until the 1992 survey, the numbers had been stable or increasing in every area the biologists had surveyed earlier. All the reports they had received in the 1980s for specific areas were of continuing abundance. Something in the ecosystem had obviously changed. Based on the studies done by Jim Estes and his colleagues in the 1970s, the scientists and managers could predict that fewer otters in the ecosystem would result in major changes to other parts of the ecosystem. The results of the study showing Amchitka with lots of otters and Shemya with few suggested that fewer otters would mean the loss of kelp beds, which were habitat for fish, crabs, and other marine invertebrates. This could have a large impact on subsistence foods for people who lived in the Aleutians and the huge commercial fisheries that took place there. The only way to help the otters and the rest of the ecosystem to recover was to figure out what had changed that caused the otters to disappear.

Many more scientists were enlisted to solve the mystery and to determine the cause of the decline, so that wildlife managers could determine if there was anything people could do to reverse it and restore the ecosystem to an abundance of marine species.

Alaska Sea Grant University of Alaska Fairbanks Alaska Department of Education and Early Development NOAA