Alaska Sea Grant

Readings

Readings

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.

Sea Otter Counts

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.

Sea Otter Counts 1957-2000

What had happened to all of the otters?

  

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.

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.

Sea otter resting

Although sea otters live in cold ocean waters, they don’t have a layer of fat or blubber like whales, seals, and sea lions. But they have one of the thickest fur coats of any animal, with 1,000,000 hairs to the square inch. By comparison, humans have only 100,000 hairs on their head. In fact, what keeps the otter warm is a double fur coat. The fine underfur next to the body traps heat, and very long guard hairs on top of that keep the underfur dry.

In rocky areas, sea otters prefer to spend most of their time in tall, thick beds of brown seaweed, or kelps. They wrap themselves up in the kelp to help them stay afloat when they rest and sleep. Inside the kelp stand, the waves are much gentler.

Sea otters have a favorite food in rocky areas—sea urchins. The otters dive down to the bottom of the kelp where the urchins are feeding, and they can stay under water for five minutes. They also eat snails and fish.

People harvest sea otters for their fur. The Unangans, some of the first Native people from Asia to reach Alaska, lived for thousands of years in the Aleutian Islands. They made warm, full-length coats, or cloaks, from the warm, luxurious fur of the otters. In 1741, Vitus Bering reached the Aleutian Islands and took sea otter pelts back to Russia. A large fur trade by Russians, Americans, and British killed nearly every sea otter in the Aleutian Islands by the late 1800s. In 1911, however, the sea otters were protected by an international treaty and they began to slowly recolonize the entire chain of islands. Visitors to the Aleutian Islands like to see and photograph the otters.

Sea otters spend a lot of time keeping their fur coat clean. If the fur becomes dirty, the sea otter is no longer waterproof and it will drown. Oil spills are especially dangerous to sea otters because the oil coats the guard hairs. When the otter cleans its fur, it swallows large amount of oil that can make it sick or kill it.

Kelp, photo courtesy of Heloise Chenelot

The Producers in the Ecosystem

Only two types of living things in the ocean make food using sunlight. These are called producers. One type is phytoplankton. Huge numbers of phytoplankton, most of them only visible under a microscope, drift with the currents and are food for the zooplankton such as copepods and young urchins.

The second type are the seaweeds, which are large algae. The largest seaweeds grow low in the intertidal zone and extend out into the subtidal zone. These are the kelps, large brown seaweeds that are glued to the rocks with their holdfast. Their long blades float at or near the surface of the water where they get sunlight to make food, which allows them to grow very fast. Their holdfast glue is very strong, and it can keep the huge kelp in one place even when strong currents and waves occur during storms.

Snails and sea urchins eat kelp, and fish, crabs, and many other animals find shelter within the dense kelp stands—called a kelp forest. Like a forest on land, the kelp forest provides food, places to hide, and a calm place away from the force of waves and winds. Many kelps die back in the winter and grow again the following spring. Large amounts of dead kelp are recycled by scavengers, including sea urchins, and decomposers.

Ribbon Kelp 

Sea urchines, photo courtesy of Heloise Chenelot

Several types of animals depend on the kelp forest as their habitat. They find shelter there because the many tall blades of the kelp break the force of the waves. Inside the kelp forest, the water is calm and small animals can avoid being washed away by the waves. They also cling to the kelp and find hiding places from the other animals that want to eat them.

Sea urchins and snails eat the kelp, either when it is alive or after it has died back each year. Sea urchins feed at the base of the kelp, and large numbers of urchins can actually cut down a tall kelp. Crabs are the resident scavengers. Young salmon and other small fish that live in schools find shelter in kelp forests.

Orcas, photo courtesy of Steve Trumble

Seals, sea lions, and killer whales live year-round in the waters near the Aleutian Islands. They eat fish, including salmon and small fish that live in schools. Gray whales and humpback whales migrate through the major passes in the Aleutian Islands to get to their summer feeding areas in the Bering Sea. These baleen whales eat small fish that live in schools and copepods, a type of zooplankton.

Two types of killer whales are found in these waters. Pods of resident killer whales stay together and stay around the same area and feed on fish, including a lot of salmon. Transient killer whales sometimes move through the area, roaming over long distances and preying on seals and sea lions. They may also prey on gray and humpback whales when they are migrating through the passes between the islands on their way to the Bering Sea.

Food chain diagram

Events and Announcements

Get Your Feet Wet

April 1 - May 31

Celebrate and share your local event with other Alaskan teachers and students! We'll send you and your students a certificate of accomplishment and place them on the Alaska Sea Grant honor roll if they complete a clean-up or other type of stewardship project. xx

Register here

Alaska Seas and Watersheds teaching resources and activity ideas for field trips and stewardship projects are available for all grade levels along with new NGSS-aligned lesson plans and units for field trips and the use of drones and submersibles to collect environmental data.

Coming Soon!

A collection of teaching resources for the Northern Gulf of Alaska Long-Term Ecological Research Project area and a link to resources for teaching about ocean acidification.

Professional Development

Alaska Sea Grant provides professional development in a variety of formats. Onsite in-service presentations and workshops are provided free-of-charge as an opportunity for Alaska K-8 teachers and informal educators to learn about our award-winning, Alaska-relevant curriculum materials and other educational resources.  Graduate-level courses can also be provided for the cost of Continuing Education Credits through the University of Alaska.

More information

Professional development
Tidepooling

Grants to Alaska Schools

Since its beginnings during the 2014–2015 school year, the Alaska Sea Grant school grant program has provided more than $100,000 to 10 Alaska school districts to increase local marine and aquatic education in 22 communities. The three-year, $10,000 grants have supported science curriculum revisions, development of NGSS-aligned lesson plans and units, field trip transportation, and the purchase of equipment and supplies.

If you are an Alaska teacher or administrator, contact us to get on the email list for the next announcement for a Request for Proposals.

anchoragewetlandsStudents explore and collect data in Westchester Lagoon, the outlet to Chester Creek. Alaska Sea Grant funds support a watershed education field trip program for more than 250 Anchorage School District students.
 
Alaska Sea Grant University of Alaska Fairbanks Alaska Department of Education and Early Development NOAA

Photographs courtesy of Reid Brewer, Verena Gill, Heloise Chenelot, Stephen Trumble, and David Menke.

The contents of this website were developed with the assistance of Title II, Part B, Mathematics and Science Partnership Program federal funds from the Alaska Department of Education & Early Development. However, these contents do not necessarily represent the policy of the Department of Education & Early Development, and you should not assume endorsement by the Federal Government.

The University of Alaska Fairbanks is an AA/EO employer and educational institution and prohibits illegal discrimination against any individual: Learn more about UA's notice of nondiscrimination.

Help Using This Site
 

© 2007–2024 Alaska Sea Grant

The University of Alaska Fairbanks is an AA/EO employer and educational institution and prohibits illegal discrimination against any individual: Learn more about UA's notice of nondiscrimination.