Sea Otter Story

Part 1

On a summer day during the early 1990s, Jim Estes was in his skiff off the island of Shemya, searching for sea otters as he had done many times in the last 20 years. Despite the sometimes terrible weather, the Aleutian Islands were his favorite place in Alaska. He had first come here in the 1970s to study the otters and their ecosystem. He had suspected then that they played a very important role in that ecosystem. Although he now lived in California and taught at the University of California in Santa Cruz, he returned to the Aleutians again and again to continue his study.

When he first came to Alaska, there had been no otters anywhere near this island. They had disappeared from the Aleutian Islands by 1900, except for a few small groups far from Shemya. Sometime in the late 1980s or early 1990s, they had returned.

He stayed close to shore because he knew that otters could only dive and find their food on the bottom in shallow water. He began spotting otters. At the end of the day, when he tallied up all the groups of sea otters that he counted near Shemya, the numbers were relatively low. This is what he expected to find, however, for an area that had only recently been recolonized by the otters.

A few days later, he surveyed the waters around Amchitka, 250 miles to the east in the Rat Islands. Here, he expected to see large numbers of otters as he had in the past, even during the 1970s when he first began to study them. But today he was surprised. Where were all the otters? He made sure he was doing the same type of boat survey he had in the past. Something had changed.

His counts of otters near the islands seemed to confirm what the biologists who worked for the Aleutian Island National Wildlife Refuge had recently observed. In 1992, they had completed an extensive survey by airplane over the entire 500-mile stretch of the Aleutian Islands, and found much smaller numbers of otters compared to the last Aleutian Island-wide survey in 1965.

Here is what they found.The following chart shows information for all of the islands combined.

They also compared all of the otter counts and estimates for Amchitka (the Rat Islands) and Shemya (the Near Islands). This chart shows information for the island groups.

What had happened to all of the otters?

Part 2

When Jim Estes noticed fewer sea otters around Amchitka Island, his concern was based on his experience as a scientist who had been studying sea otters in the Aleutian Islands for 20 years. Remember, he arrived in 1970 to begin a study in the Rat and Near islands with another biologist, John Palmisano. They chose two sites to study, Amchitka in the Rat Islands, and Attu and Shemya in the Near Islands to the west, at the very end of the Aleutian chain of islands. They knew that Amchitka had an abundance of sea otters and that Attu and Shemya had few or none. Almost all of the sea otters from the Aleutian Islands to California had been harvested for their furs. Only 11 small groups of otters remained, and one was in the Rat Islands near Amchitka.

In a magazine article about their first study, they had this to say about their first impressions. “Upon arriving at the Amchitka Island in the Rat Islands group, we were immediately struck by the dense kelp beds. The kelp is so abundant that in many areas we could not see the rocky ocean floor either from the shore or when diving in the water. Yet at the Near Islands of Attu and Shemya, 250 miles to the west, there are only a few scattered kelp beds. What we did notice here was a dense carpet of large sea urchins, small invertebrates that live on the ocean floor or in rocky crevices and feed on the kelp. So completely have the sea urchins grazed the kelp that the ocean floor appeared light emerald, rather than dark brown as at Amchitka.” (Palmisano and Estes 1976.)

Jim Estes and John Palmisano studied the otters and the ecosystems around the two islands for three seasons. Their results made it possible to understand the interconnections in kelp bed marine ecosystems and the important role of sea otters in the ecosystem. Their data and conclusions provided important clues to solve the mystery about the disappearing otters.

Part 3

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.