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Ronald J. Jameson

Publications and source records attributed to Ronald J. Jameson.

15 recordsLinked to original sources
USGS2009

Stress-related hormones and genetic diversity in sea otters (Enhydra lutris)

Sea otters ( Enhydra lutris ) once ranged throughout the coastal regions of the north Pacific, but were extirpated throughout their range during the fur trade of the 18th and 19th centuries, leaving only small, widely scattered, remnant populations. All extant sea otter populations are believed to have experienced a population bottleneck and thus have lost genetic variation. Populations that undergo severe population reduction and associated inbreeding may suffer from a general reduction in fitness termed inbreeding depression. Inbreeding depression may result in decreased testosterone levels in males, and reduced ability to respond to stressful stimuli associated with an increase in the stress-related adrenal glucocorticoid hormones, cortisol and corticosterone. We investigated correlations of testosterone, cortisol, and corticosterone with genetic diversity in sea otters from five populations. We found a significant negative correlation between genetic diversity and both mean population-level ( r 2 = 0.27, P < 0.001) and individual-level ( r 2 = 0.54, P < 0.001) corticosterone values, as well as a negative correlation between genetic diversity and cortisol at the individual level ( r 2 = 0.17, P = 0.04). No relationship was found between genetic diversity and testosterone ( P = 0.57). The strength of the correlations, especially with corticosterone, suggests potential negative consequences for overall population health, particularly for populations with the lowest genetic diversity.

Marine Mammal Science↗
USGS2006

An incidence of twinning in the sea otter (Enhydra lutris)

On 3 October 1984 at 0928 h (PST) near Pt. San Simeon, California (35°39’N, 121°11’W), we observed a female sea otter ( Enhydra lutris ) resting in a kelp bed ( Macrocystis pyrifera ) with a small pup on her chest; approximately 2 m away another small pup floated unattended in the kelp. The only other otters we saw in the area was a mated pair (adult male tending an adult female) resting about 20 m from the mother and pups. At 0929 h the mother swam to the unattended pup and placed it on her abdomen next to the other pup. We concluded that live birth of twin pups had occurred, an incident previously unrecorded for the species.

California↗
USGS2006

Movements, home range, and territories of male sea otters off central California

Sixty male sea otters ( Enhydra lutris ) were tagged on the rear flippers with colored tags. Of these, 46 (77%) were resighted. Movements of 127 km were documented for adults and 187 km for subadults. Adults maintained breeding territories that averaged 40.3 ha ( n = 10, SE = 4.0). They returned to the same territory seasonally for up to seven consecutive years. Territorial males moved from areas of high male abundance to areas of high female abundance on a seasonal basis. During the winter, 74% of adult males left breeding areas and joined concentrations of males located near the ends of the range. Thirty percent of the subadult males were observed in male groups near the extremities of the range. During the summer and fall, the density of adult males (15/1,000 ha) and adult male to independent otter (non-pup) ratio (1:5) in female areas was highest. The number of adult males in areas of female abundance was inversely related to the number of dependent pups, perhaps because when pup numbers are low (late summer and fall) the number of estrous females is high. Subadult males may remain in female areas on a year round basis until their second or third year. However, they were not generally associated with adult females.

California↗
USGS2006

Reproductive characteristics of female sea otters

Several important aspects of reproduction in the female sea otter, such as gestation, pupping frequency, period of pup dependency, and annual pupping rate, were unclear when this study was begun. We present data from 75 tagged adult females that indicate gestation is variable, but on average is about 6 months, the length of pup dependency is 6 mo, thus the pupping interval is usually 12–13 mo. Most females breed for the first time in their fifth year of life. About 85–90% of adult females pup in a given year.

Alaska, California↗
USGS2002

Microsatellite DNA and mitochondrial DNA variation in remnant and translocated sea otter ( Enhydra lutris ) populations

All existing sea otter ( Enhydra lutris ) populations have suffered at least 1, and in some cases 2, population bottlenecks. The 1st occurred during the 18th and 19th centuries as a result of commercial hunting that eliminated sea otters from much their native range and reduced surviving populations to small remnants. The 2nd bottleneck occurred when small numbers of otters were reintroduced, via translocation, to areas where the species had been eliminated. We examined genetic variation at 7 microsatellite loci and the mitochondrial DNA (mtDNA) control region in 3 remnant populations, Amchitka Island (Aleutian Islands, Alaska), central coastal California, and Prince William Sound (Alaska), and in 2 reintroduced populations, southeast Alaska and Washington, that were founded with transplants from Amchitka, and in the case of southeast Alaska, individuals from Prince William Sound as well. We found no evidence of reduced genetic diversity in translocated populations. Average expected microsatellite heterozygosities ( H E ) were similar in all populations (range, 0.40–0.47), and mtDNA haplotype diversities were higher in reintroduced populations (0.51 for both Washington and southeast Alaska) than in remnant populations ( X̄ = 0.35; range, 0.18–0.45). The levels of genetic diversity we observed within sea otter populations were relatively low when compared with other mammals and are thought to be the result of fur trade exploitation.

Alaska, California, Washington↗
USGS1999

Results of the 1999 survey of the reintroduced sea otter population in Washington state

Fifty-nine sea otters were released off the west coast of the Olympic Peninsula of Washington State during the summers of 1969 and 1970; all had been translocated from Amchitka Island, Alaska. In 1970, 30 otters were released. Surveys to assess the results of this translocation began in 1977. Up to 1989, the population has grown at near the maximum rate of increase (r max ) for sea otter populations of 17-20% yr -1 . Since 1989, however, the rate of increase appears to have declined to about 11% yr -1 . The results of the survey this year are encouraging and indicate the population has been growing at a finite rate of about 11% since 1989.

IUCN Otter Specialist Group↗
USGS1998

Translocated sea otter populations off the coasts of Oregon and Washington

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). Followup 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, Washington↗
USGS1997

Estimating age of sea otters with cementum layers in the first premolar

We assessed sources of variation in the use of tooth cementum layers to determine age by comparing counts in premolar tooth sections to known ages of 20 sea otters ( Enhydra lutris ). Three readers examined each sample 3 times, and the 3 readings of each sample were averaged by reader to provide the mean estimated age. The mean (SE) of known age sample was 5.2 years (1.0) and the 3 mean estimated ages were 7.0 (1.0), 5.9 (1.1) and, 4.4 (0.8). The proportion of estimates accurate to within ± 1 year were 0.25, 0.55, and 0.65 and to within ± 2 years 0.65, 0.80, and 0.70, by reader. The proportions of samples estimated with >3 years error were 0.20, 0.10, and 0.05. Errors as large as 7, 6, and 5 years were made among readers. In few instances did all readers uniformly provide either accurate (error <1 yr) or inaccurate (error >1 yr) counts. In most cases (0.85), 1 or 2 of the readers provided accurate counts. Coefficients of determination (R2) between known ages and mean estimated ages were 0.81, 0.87, and 0.87, by reader. The results of this study suggest that cementum layers within sea otter premolar teeth likely are deposited annually and can be used for age estimation. However, criteria used in interpreting layers apparently varied by reader, occasionally resulting in large errors, which were not consistent among readers. While large errors were evident for some individual otters, there were no differences between the known and estimated age-class distribution generated by each reader. Until accuracy can be improved, application of this ageing technique should be limited to sample sizes of at least 6-7 individuals within age classes of ≥ 1 year.

Alaska, California↗
USGS1996

Comparative demography of sea otter populations

Population trends are poorly documented and demographic information is typically lacking for many carnivorous mammals. The sea otter ( Enhydru lutris ) has a well known history of decline and recovery, and while many other species have declined as precipitously, few have recovered so spectacularly. Generally speaking, northern populations (remnants within the range of E. l. lutris and E. l. kenyoni ) have recovered at high rates while recovery of the southern sea olter ( E. I. nereis ), which is listed as legally threatened under the Endangered Species Act (ESA), has progressed more slowly. Our purpose is to contrast trends in abundance and demographic patterns between Southern California and northern (Washington, British Columbia, Alaska, and Asia) sea otter populations. Specifically, we provide (1) a brief review of the main findings to date: (2) a summary of ongoing and planned studies; and (3) recommendations for future research. A more detailed account of these and other issues concerning the conservation and management of sea otters is provided in the U.S. Fish and Wildlife Service's Recovery Plan for the Califomia Sea Otter (U.S. Fish and Wildlife Service 1996).

Endangered Species UPDATE↗
USGS1995

Sea otters in the northern Pacific Ocean

About 250 years ago sea otters ( Enhydra lutris ) were distributed continuously from central Baja California, north and west along the Pacific Rim to Machatka Peninsula in Russia, and south along the Kuril Island to northern Japan (Kenyon 1969; Fig. 1a). Several hundred thousand sea otters may have occurred in the north Pacific region when commercial hunting began in the 18th century (Riedman and Estes 1990). At least two attributes of the sea otter have influenced humans, likely for as long as they have resided together along the coast of the north Pacific Ocean. First, sea otters rely on a dense fur, among the finest in the world, for insulation in the cold waters of the Pacific Ocean. The demand for sea otter fur led to their near extinction in the 19th century. The fur harvest, begun about 1740 and halted by international treaty in 1911, left surviving colonies, each likely numbering less than a few hundred animals, in California, south-central Alaska, and the Aleutian, Medney, and Kuril Islands (Fig. 1a). These individuals provided the nucleus for the recovery of the species. Today more than 100,000 sea otters occur throughout about 75% of their original range (fig. 1b). Immigration has resulted in near-complete occupation of the Aleutian and Kuril archipelagos and the Alaska peninsula. Successful translocations have resulted in viable populations in southeast Alaska, Washington, and British Columbia. Large amounts of unoccupied habitat remain along the coasts of Russia, Canada, the United States, and Mexico. The second potential source of conflict between sea otters and humans is that sea otters prey on and often limit some benthic invertebrate populations. Because some of these invertebrates are aso used by humans (Estes and VanBlaricom 1985), human perceptions about the effects of sea otter foraging on invertebrates sometimes differ. By limiting populations of herbivorous invertebrates ( e.g. , sea urchins [Echinoidea]) otters help maintain the integrity of kelp forest communities. At the same time, sea otter predation on other marine invertebrates can lead to direct competition with humans for resources. These interactions add complex dimensions to the conservation and management of sea otters, in large part because of wide-ranging social, ecological, and economic consequences of sea otter foraging. Long-term data on abundance and distribution are available for relatively few sea otter populations. Here we summarize such data from three populations: Being Island, Russia; Prince William Sound, Alaska; and Olympic Peninsula, Washington. The Bering Island population resulted from natural emigration and represents complete recovery. Prince William Sounds represents near recovery of a remnant population, whereas the Washington population was established via translocations from Alaska and is just beginning to recover. We will compare growth rates and current status among these populations. Because of its unique status and growth characteristics, the California sea otter is not treated in this article.

Book chapter↗
USGS1991

Patterns of seabird and marine mammal carcass deposition along the central California coast, 1980-1986

At monthly intervals from February 1980 through December 1986, a 14.5-km section of central California coastline was systematically surveyed for beach-cast carcasses of marine birds and mammals. Five hundred and fifty-four bird carcasses and 194 marine mammal carcasses were found. Common murres, western grebes, and Brandt's cormorants composed 45% of the bird total. California sea lions, sea otters, and harbor seals composed 90% of the mammal total. Several factors appeared to affect patterns of carcass deposition. The El Niño – Southern Oscillation (ENSO) of 1982–1983 was the dominant influence in terms of interannual variation in carcass deposition. During this ENSO, 56% of the seabirds and 48% of the marine mammals washed ashore. Patterns of intra-annual variation were species specific and were related to animal migration patterns, reproduction, and seasonal changes in weather. Nearshore currents and winds influenced the general area of carcass deposition, while beach substrate type and local patterns of sand deposition influenced the location of carcass deposition on a smaller spatial scale. Weekly surveys along a 1.1-km section of coastline indicated that 62% of bird carcasses and 41% of mammal carcasses remained on the beach less than 9 days. Cause of death was determined for only 8% of the carcasses. Oiling was the most common indication of cause of death in birds (6%). Neonates composed 8% of all mammal carcasses.

Canadian Journal of Zoology↗
USGS1988

A double survey estimate for sighting probability of sea otters in California

We developed an estimator for the probability of sighting sea otters ( Enhydra lutris ) by shore- based counters, based on simultaneous double-surveys. We then estimated probability of sighting sea otters in California and evaluated the estimator's principal assumptions. The overall probability of sighting sea otters on 5 replicated double-surveys at each of 6 study areas was 0.945. Estimated probability of sighting did not vary (P > 0.05) among study areas or over time and was not correlated (P > 0.05) with distance of otters from observers. Probability of sighting was affected (P < 0.05) by sea otter activity and group size. Activity-specific probabilities of sighting were: resting = 0.990, foraging = 0.769, and other = 0.885. All animals missed by 1 observer team were in groups of ≤ 2 otters, whereas 52% of the animals sighted during the study were in groups ≥ 3. Observer teams may have varied slightly in sighting ability, but this variation did not substantially affect population estimates.

California↗
USGS1987

Mortalities of kelp-forest fishes associated with large oceanic waves off central California, 1982-1983

Observations of three incidents of the mass mortality of nearshore fishes are reported; each corresponded to periods of high-amplitude, long-period swells during the 1982-1983 El Niño event along the coast of central California. Members of the nearshore kelp forest fish assemblage, primarily of the genus Sebastes , accounted for 96% of the observed mortalities and S. mystinus (blue rockfish) alone accounted for 72%.

California↗
USGS1986

Status of a translocated sea otter population and its habitat in Washington

During the summers of 1969 and 1970, the Alaska Department of Fish and Game and the Washington Department of Game translocated 59 sea otters from Amchitka Island, Alaska, to release sites in Washington (Jameson et al. 1982, Wildl. Soc. Bull. 10:100-107). Of the 29 released near Pt. Grenvil (Fig. 1) in 1969, 16 are known to have died. In 1970, 30 otters were held in a floating enclosure anchored near James Island, off La Push. They were released nearby in excellent condition on July 1970. Results of surveys from 1977 to 1981 were reported by Jameson et al. (1982). The purpose of this note is to report subsequent additional observations for 1983 and 1985 on the abundance, distribution, and habitat of the sea otter population in Washington

Washington↗