Readings

A small, black chiton has a number of names that reflect its history with people. Its scientific name is Katherina tunicata, with the first name, or genus, in honor of a woman scientist, Lady Katherine Douglas. In 1815, she sent the first specimens to England. Also in honor of Lady Katherine, a common name for the small mollusk is the katy chiton. More recently, the tough, black, leathery covering on its back has earned it the common name black leather chiton. The animal is 1.5-3 inches long. Like all chitons, it has a muscular foot on the underside of its body and a shell that consists of eight white, overlapping butterfly-shaped plates. The tough, rubbery covering, called the girdle, is around the upper edge of the plates and may even completely cover the white plates. Chitons feed by using a hard, file-like rasping radula that extends out of the mouth on the underside of the animal to scrape algae and other small organisms off rocks in the intertidal zone. When disturbed, they can cling tightly to the rock and become very hard to remove. But when they are exposed by the low tide and dry out, they fall off the rock and become easy pickings for birds and other predators. In 2003 Anne Salomon, a scientist at the University of Washington, went to Port Graham to study katy chitons.

(go to Part 2a)

In the villages of Nanwalek and Port Graham, Alaska, katy chitons are known as “bidarkis.” The majority of people who live in the villages are Alaska Native of the Sugpiaq group. The chitons have been an important subsistence food in the area for more than 100 years. The name bidarki also reflects the history of the area—it is the Russian word for “boat.” Russians settled in the area in the 1780s and stayed throughout the 1800s. When the chiton is trying to protect itself from a predator, it curls up into the shape of the boat to protect its soft and tasty foot.

The people who live in these villages noticed that there were fewer bidarkis in the places they went to harvest them, and that they were generally smaller than in the past. This had been occurring over the last 10-15 years.

They wanted to know:

• Why are there fewer and smaller bidarkis to harvest?
• How fast do bidarkis grow?
• How long do they live?
• Is pollution affecting the bidarkis?
• What can people do to manage their harvest of bidarkis so they can sustain this traditional use into the future?

(go to Part 2b)

Quotes from Sugpiaq elders and tribal members in Nanwalek and Port Graham, Alaska

(go to Part 3a)

Anne Salomon was interested in studying the katy chiton because other scientists at the University of Washington had studied the animal in northern Washington and observed that it was important to the ecosystem. In this study, the katy chiton had been shown to be a keystone species, the “lawn mower” of the intertidal zone. Where large numbers of them lived, they scraped the rocks bare of small animals such as limpets and barnacles that had settled there. They also grazed the seaweeds so heavily that certain types of seaweeds couldn’t survive. So, when there were large numbers of katy chitons, they affected the other animals who ate the seaweeds and small animals. In the Washington study, katy chitons changed the entire makeup of the intertidal community, shifting it from large brown kelp seaweeds to short, stubby seaweeds and a lower variety of animals. Scientists weren’t sure whether they had the same effect in Alaska intertidal communities as they had in Washington. They also did not know how the harvest of the bidarkis as food or killing by sea otters affected the story.

The scientist wanted to know:

Is the katy chiton a “keystone” animal in Kachemak Bay and other rocky intertidal habitats in Alaska? Does its presence or absence have a large effect in determining which other animals and seaweeds can survive in a specific area of the intertidal area?

What controls the number and size of katy chitons at a specific area?

[Possibilities include the physical environment (for example, the force of waves on exposed shores could determine if the chitons can remain there or will be washed away) or predation by people, sea stars, or sea otters.]

What role do people play in the system that katy chitons depend on? What other marine animals and seaweeds are part of the system and how are they related or linked?

(go to Part 3b)

Anne Salomon developed hypotheses she could test.

Hypothesis #1: If bidarkis are not present at a site, different plants and animals will live there than at sites where bidarkis are present.

What She Did: She set up experiments to keep the chitons out of small areas by using copper rings (which are toxic to bidarkis so they won’t move across them), scraped the area of rock inside the ring clean of living things, and observed what grew or settled inside the ring compared to an nearby area the same size.

Hypothesis #2: Areas where more bidarkis are harvested will have lower numbers of bidarkis that are smaller, on average, in size than areas where they are rarely or never harvested.

What She Did: She looked at and compared 11 sites, extending over 50 km of coastline, including sites close to villages where bidarkis were heavily harvested, sites far from villages that were rarely or never harvested, and other sites that were not harvested very often due to weather. At each site, they estimated the number and area of bidarkis and weighed and measured them to calculate average size at each site.

Hypothesis #3: Certain factors have changed during the period of time that bidarkis were declining in numbers and size that can help to explain the decline.

What She Did: She worked with a social scientist, Henry Huntington, to interview elders and long-term residents to document traditional knowledge.

What She Found Out

1. Bidarki numbers and average sizes were lower at sites closest to the villages.
2. Bidarkis were important to the living things in the rocky intertidal habitat. Where the bidarkis were present in average or high numbers, they ate nearly all of one annual kelp (Alaria marginata) from sites and reduced the number of different marine invertebrate species by 38%.
3. Where subsistence harvest of the bidarkis was high, the amount of kelp was seven times higher than in sites where no harvest occurred.

(go to the Conclusion)

What the Scientists and Villagers Learned Together
The focus on what was happening in the intertidal zone. The traditional uses of intertidal resources were not enough to solve the question about the causes of the decline in the bidarki size and numbers. It turned out that a combination of long-term knowledge about what had changed in the area, plus scientific observation, was needed. Sea otters turned out to be an important player in the investigation.

Traditional knowledge: Sea otters were absent from Kachemak Bay in the early 1900s after Russian fur harvests removed them, but began to reestablish in the 1960s. People, including the villagers and the scientists, observed increasing use of the areas where the villagers harvest bidarkis.

Scientific observations: The scientists collected sea otter observations during their study and documented more otters in areas where bidarki numbers and size were lower.

The final story or conclusions of the study:

1. The increased subsistence harvest in areas close to the village was partly responsible for the decline in numbers and in size of bidarkis. But sea otter predation had the same effect and both happened at the same time.
2. Due to the keystone role of the bidarki in the rocky intertidal zone, if people harvest bidarkis and/or sea otters are predators on them, the plant and animal community shifts from one with a lot of kelp to one with less kelp. When there is less kelp, there is less habitat for marine invertebrates.
3. The sea otters and the subsistence harvests were a case of serial depletion of resources as both the otters and the people switched their selection of prey, in the same sequence. As one species became scarce, they both switched to another one, until the bidarkis were one of the few resources left that both were harvesting.

What can the villagers do to sustain their harvest? 

The Halibut Cove Story

Halibut Cove, Alaska, is located on the south side of Kachemak Bay on the east side of Cook Inlet. It was occupied by Alaska Native people in prehistoric times for thousands of years, based on the remains found in their midden (or garbage) piles excavated by archaeologists.

In the early 1900s, a large-scale herring fishery developed to catch and process herring that came to spawn in Halibut Cove in the spring and came back in the fall to overwinter in the bay. Steller sea lions, seals, porpoises, belugas, and many species of birds ate large quantities of the fish and sticky eggs that female herring deposited on the eelgrass beds in the intertidal areas. Pods of beluga whales and harbor seals fed on the herring in Halibut Cove Lagoon.

The herring were called “bloaters” due to their large size. They were 12-14 inches in length. Hundreds of people began arriving to harvest the herring in Kachemak Bay during the fall, winter, and spring fishing seasons. At the peak of the fishery, up to 3,000 people worked in the fishery and 38 “saltries” operated in Halibut Cove to pack the herring in brine (saltwater) and barrels for shipment to the East Coast. The town had ocean docks for steamships and a pool hall.

The fishery began in 1911 and ended in 1928, when the saltries stopped operating due to lack of fish. The herring never again returned to Halibut Cove or to other bays and coves in Kachemak Bay in large numbers in the fall.

The end of the herring has never been explained, but possible causes include overfishing and pollution of the spawning areas. In the mid 1920s, large purse seines were allowed to catch the herring in addition to the gillnets that had been used. Complaints were made to the territorial fish commissioner that small herring caught in the purse seines were being “dumped,” which meant that large numbers of both small and large fish were killed before they could reproduce the following spring. The saltries all dumped their fish waste on the beach or in the shallow waters offshore on top of the eelgrass beds where the herring spawned. Large quantities of fish waste could have smothered the eelgrass beds and blocked the light.

Halibut Cove became a ghost town with a few remaining men. It later developed into a small town with art galleries and a restaurant visited by tourists and cabin owners during the summer, with 30-50 year-round residents.

(Adapted from The Story of Halibut Cove by Diana Tillion and the Kachemak Bay Ecological Characterization by the Kachemak Bay Research Reserve)