The historical distribution of sea otters extended from the northern islands of Japan north and east across the Aleutian chain to the mainland of North America then south along the west coast to central Baja California, Mexico (Riedman and Estes 1990). By the beginning of the twentieth century, after 150 years of being intensively hunted for their valuable fur, sea otters had been extirpated from most of their range (Kenyon 1969). In 1911 sea otters were protected by the passage of the International Fur Seal Treaty. Unfortunately, only 13 remnant populations survived the fur-hunting period, and two of those, British Columbia and Mexico, would also ultimately disappear, leaving only a small group of sea otters south of Alaska, along the rugged Big Sur coast of California (Kenyon 1969).

The earliest attempts to reestablish sea otters to unoccupied habitat were begun in the early 1950's by R. D. (Sea Otter) Jones, then manager of the Aleutian National Wildlife Refuge (Kenyon 1969). These early efforts were experimental, and all failed to establish populations. However, the knowledge gained from Jones's efforts and the seminal work of Kenyon (1969) and others during the 1950's and early 1960's ultimately led to the successful efforts to come.

During the mid-1960's the Alaska Department of Fish and Game began translocating sea otters to sites where the species had occurred before the fur-trade period. The first translocations were restricted to Alaska, but beginning in 1969 and continuing through 1972, the effort expanded beyond Alaska. During this period, 241 sea otters were translocated to sites in British Columbia, Washington, and Oregon (Jameson et al. 1982). The work was done cooperatively between state and provincial conservation agencies, with much of the financial support for the Oregon and Washington efforts coming from the Atomic Energy Commission (now ERDA). Follow-up studies of the Oregon population began in 1971 and continued through 1975. After 1975, surveys in Oregon occurred infrequently. In Washington no follow-up surveys were conducted until 1977, although the population has been monitored closely since then (Jameson et al. 1982, 1986; Jeffries and Jameson 1995).

Oregon

Sea otters were extirpated by fur-trade hunters in Oregon by the early twentieth century. Most of Oregon's sea otter habitat occurs in the southern half of the state, where the only extensive nearshore rocky reef systems are found. Ninety-three translocated sea otters were liberated here: 29 near Port Orford in 1970 and 24 near Port Orford and 40 near Cape Arago in 1971. Counts never reached anywhere near the number of otters released, but from 1972 to 1974 they ranged from 20 to 23 otters. In 1975, however, the population began to decline, and in 1981 only one sea otter could be found (Jameson et al. 1982). By then the population was clearly no longer viable, and no subsequent sightings were made until the summer of 1992, when a single sea otter was observed at Cape Arago. No sea otters have been seen since then. Sea otters are once again extirpated in Oregon, and the translocation should be classed as a failure.

Washington

As in Oregon, the Washington sea otter population had also been extirpated by fur-trade hunting by the early twentieth century. Fifty-nine sea otters were released off the west coast of the Olympic Peninsula of Washington during the summers of 1969 and 1970 (Jameson et al. 1982); all had been translocated from Amchitka Island, Alaska. In 1969, 29 sea otters were released directly to the open ocean near Point Grenville (Fig. 1), with no time to acclimate or to recondition their fur. Sixteen of those 29 translocated sea otters were found dead on beaches near the release site within 2 weeks after translocation. No doubt some carcasses went undiscovered.

In 1970, release procedures and the release site were changed. The release location was changed to La Push (Fig. 1), located within the boundaries of Olympic National Park and near the middle of the best sea otter habitat in Washington. In midsummer, 30 sea otters were flown to La Push and released into holding pens anchored in a protected cove just beyond the La Push harbor entrance. The 30 otters were fed and allowed to acclimate for several days in the pens before release. All were liberated in excellent condition, and known mortality after release was low. Thus, the initial nuclear population in Washington could never have been larger than 43 otters and may have dropped to fewer than 10 individuals by the early 1970's (Jameson et al. 1982). No follow-up surveys of the Washington population were done until 1977 (Jameson et al. 1982, 1986; Table).

All sites within the survey area are located off the west coast of Washington's Olympic Peninsula between Destruction Island and Neah Bay (Fig. 2). From 1977 to 1984, surveys were conducted by U.S. Fish and Wildlife Service biologists (Table). Since 1985 surveys have been conducted cooperatively by the U.S. Fish and Wildlife Service's research division (now the Biological Resources Division of the USGS) and the Washington Department of Fish and Wildlife biologists (Table).

Population Growth

Growth of the population has continued at a finite rate of about 12% per year since 1989, when the current survey method began. From 1977 to 1988 the rate was higher, at 21% per year (R. Jameson, U.S. Geological Survey, Corvallis, Oregon, unpublished data; Fig. 3). Whether the difference between the rates indicates a slowdown of population growth or simply a difference in survey techniques (the method was modified in 1989) is still open to question. Pups were only noted separately from independent otters at ground count locations; thus the number of pups noted in the Table is probably low. However, pup counts at ground stations from 1993 to 1995 averaged 24 pups for every 100 independent otters, which suggests pup production has remained good.

The majority of sea otters in Washington occur between Makah Bay and Destruction Island (Fig. 2). Several significant changes in distribution have occurred recently, however. At the southern end of their range, sea otters now regularly occur inshore from Perkins Reef. As many as 20 sea otters have been counted in this area recently, although no more than one had been seen there before. At the northern end of the range, scattered individuals were regularly seen near Cape Flattery and between there and Neah Bay. In 1995, however, more than 100 otters moved into this area. This appears to be a seasonal phenomenon, occurring during the late winter and early spring. In late 1995, a small group of females rounded Cape Flattery and took up residence near Slant Rock. This area was previously inhabited almost entirely by male sea otters.

In 1988 and again in 1991, the outer coast of the Olympic Peninsula was hit by spills of bunker fuel oil, both from shipping accidents. The 1988 spill occurred in December, the 1991 spill in late July. In both cases about 230,000 gallons were spilled.

The sea otter population was relatively unaffected by both spills, although thousands of seabirds died in each. No oiled sea otters were found in 1988, and only one was found in 1991. This animal did, however, die of complications caused by oiling (N. J. Thomas, National Wildlife Health Research Center, Madison, Wisconsin, necropsy report).

When we began our surveys in 1977 (Jameson et al. 1982), the sea otter population was distributed between Destruction Island and Cape Alava, a distance of about 60 kilometers. In 1992 the population was distributed between Destruction Island and Makah Bay, a distance of about 80 kilometers. By 1996 the range had increased to more than 110 kilometers, Destruction Island to Neah Bay (Fig. 2). Before 1991 the distribution had changed little from what it was in 1977. Until then all the population growth had taken place within the 1977 boundaries. In 1991 a large group broke away from the main population and established itself in Makah Bay about 15 kilometers north of where they were the previous year. The distribution in 1992 was similar to 1991. Females with pups now occur from near Cape Flattery to Destruction Island.

Important Surveys

The Washington sea otter population is important because it is the only translocated population having the dual distinction of becoming successfully established and of being intensively monitored. Other translocations have been successful, but few data are available on their patterns of growth. Others that have been intensively monitored, in Oregon (Fig. 1) and San Nicolas Island, California, have failed, or appear to be heading toward failure (Jameson et al. 1982; Rathbun et al. 1990). The Washington sea otter population will continue to be monitored, and in 1994 a project was initiated to collect data on female reproductive rates, pup survival rates, foraging behavior, and activity and time budgets. This information, coupled with the population growth data, will provide a basis for comparison among populations that are either stable, growing at expected rates, or growing at rates below what is expected for populations reoccupying historical habitat.

The southern sea otter (Wilson et al. 1991) population in California, listed as threatened under the Endangered Species Act in 1977, is such a population. Since 1982 this population has grown at about 5% per year (Riedman and Estes 1990), considerably more slowly than the Washington population and slower than most growing sea otter populations (Estes 1990). Contrasting the reproductive and pup survival rates of the Washington and California populations will hopefully provide insight into why the growth rates are so different. Once that point is reached, researchers can attempt to uncover the cause or causes of the differences. Recent information from California and Kodiak Island, Alaska, suggests that preweaning survival of pups may be a quite significant factor in determining rates of sea otter population growth (Riedman et al. 1994; Monson and DeGange 1995).