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My Turn: Southeast Alaska's sea otters: The restoration of an ecosystem

Posted: March 13, 2013 - 11:15pm

In 1922, fewer than 1,000 sea otters remained in the north Pacific, barely surviving over 150 years of industrial fur harvest. With protection, sea otters recovered during the ensuing decades, and in 1969, the last of over 400 sea otters were reintroduced to Southeast Alaska. Those animals are now represented by some 21,000-25,000 that occupy much of their original habitat.

From Feb. 20-23, scientists from universities and federal agencies convened in Juneau to address the public and the state legislature of the process and ecological consequences of the return of sea otters to Southeast Alaska. Venues included a symposium, a briefing to the House Fisheries Committee, radio interviews, seminars, student and faculty meetings, and a Fireside Chat. Those who took advantage of these opportunities learned a great deal about sea otters and the health of the nearshore marine ecosystem in which sea otters live.

For millennia prior to the maritime fur trade, sea otters existed in Southeast Alaska. They are a keystone species, unique among marine mammals because they rely exclusively on marine invertebrates such as clams, crabs, mussels, and urchins for nutrition. Because of their preference for sea urchins, sea otters are largely responsible for the presence of kelp forests. Sea urchins are marine herbivores whose populations, if left unchecked, can transform rocky reefs to barren grounds. However, in the presence of sea otters, urchin numbers are controlled, so kelps flourish. Kelps are important to the productivity of the nearshore, provide habitat for diverse species of invertebrates, fishes, including salmon and herring, marine birds and mammals, and kelps contribute to the reduction of carbon dioxide in the atmosphere and oceans, thus slowing ocean acidification.

Over the century that sea otters were absent from Southeast Alaska, many of their prey species responded by increasing their numbers, eventually to the point where commercial fisheries developed. Today these include species such as Dungeness crab, geoduck clams, and sea cucumbers. Now, as sea otters are recovering in Southeast Alaska, it is predictable that they will reduce such prey to more natural levels while providing nurseries for various finfish.

Overall, the rate of growth in the Southeast Alaska sea otter populations has declined in recent years, although in some areas, such as Glacier Bay and Kuiu Island, growth continues at high rates. Regional differences in population dynamics are expected due to the animals’ typically restricted movements and small home ranges. Because of limited movement, reproduction and mortality can result in population trends that might be stable in one region and increasingly rapidly in an adjacent region. For example, sea otter abundance in Icy Straits has been stable for over a decade, while in adjacent Glacier Bay, the population continues to grow.

Conflicts between sea otter recovery and shell-fisheries have social and economic consequences. Nevertheless, the return of sea otters to Southeast Alaska also generate economic opportunities, including tourism/wildlife viewing and the enhancement of fin fisheries due to the increase in kelp abundance to more natural levels.

While the recent gathering of sea otter scientists in Juneau clearly demonstrated the depth of knowledge acquired about sea otters and their role in nearshore marine ecosystems, it also demonstrated the need to obtain better information on the spatial scales at which sea otter populations are structured and to fully understand how populations are changing over time. It highlighted the need to carefully consider the costs and benefits associated with the recovery of sea otters.

The most critical message, however, is that the reintroduction of sea otters to Southeast Alaska is not simply about the recovery of a species; it is about the restoration of an ecosystem.

• Brown is a Juneau resident and is president of the Alaska Wildlife Alliance.

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