The first is considered a census, where it is assumed that all animals in an area are counted, and precision is not usually estimated. Eventually, remnant and introduced populations increased in abundance and distribution, with some becoming contiguous over spatial scales of thousands of kilometers and comprising tens of thousands of individuals. Much has been learned about the drivers and effects of sea otter population growth and range expansion because of systematic and regular population surveys, tagging and tracking programs, and diet studies throughout their range. Today, southern sea otters occupy approximately 13% of their historic range; their current distribution extends along the central California coast from Monterey Bay to Point Conception. doi: 10.2174/1874401X01306010028, Richardson, L., and Loomis, J. Translocations would decrease the time required for sea otters to reoccupy their entire historical range and to restore nearshore community structure and biodiversity in areas where they are currently absent. However, genetic variability is highest in the Southeast Alaska population, which was created by translocations from two widely separated source populations including Prince William Sound and Amchitka Island (Jameson et al., 1982; Larson et al., 2002a). How are sea otters using estuarine habitats and prey resources? In addition, continuing sources of information are needed for: (1) the abundance and distribution of prey, (2) sea otter dietary preference and consumption, (3) seasonal and annual primary productivity and oceanographic conditions, (4) predator abundance, and (5) the magnitude and sources of mortality, including the presence of diseases that decrease sea otter longevity or affect their prey. The monitoring program, at its basic level, includes quarterly seasonal surveys of population abundance, distribution, and foraging activity. Appl. Calif. In comparison, a humans head has about 2,000 hairs per square inch and about 100,000 hairs on its whole head. Figures of Pages from the Monitoring and Research Plan for Southern Sea Otter Military Readiness Area. 10, 409415. When the translocation program was established, it created a management zone from Point Conception to the Mexican border from which sea otters would be excluded. Science 200, 403411. doi: 10.1890/07-1818.1, PubMed Abstract | CrossRef Full Text | Google Scholar, Arkema, K. K., Guannel, G., Verutes, G., Wood, S. A., Guerry, A., Ruckelshaus, M., et al. doi: 10.1111/j.2006.0030-1299.14443.x, Heithaus, M. R., Frid, A., Wirsing, A. J., and Worm, B. The earliest censuses of sea otters were conducted by the Russian Coast Guard in the Commander Islands from 1924 to 1930 (Barabash-Nikiforov, 1947). The sea otter . Estes, J. Sea otters have webbed feet, water-repellent fur to keep them dry and warm, and nostrils . The population decline likely began in the mid-1980s and declined at a rate of 17.5%/year in the 1990s. doi: 10.1111/eva.12642, Garshelis, D. L., Johnson, A. M., and Garshelis, J. Secure .gov websites use HTTPS These worksheets have been specifically designed for use with any international curriculum. 23, 202210. doi: 10.1080/08920750600860282, Lubina, J. Sea otter conservation also is promoted by organizations such as the International Union for the Conservation of Nature (IUCN, Switzerland). As a result, surveys became logistically challenging and increasingly expensive, employing aircraft in some cases, with costs rising to hundreds of thousands of dollars. doi: 10.1016/B978-0-12-456160-1.50010-2. doi: 10.1016/B978-0-12-801402-8.00006-8, Monson, D. H., and DeGange, A. R. (1995). Dis. A., Hatfield, B. Activity budgets derived from time-depth recorders in a diving mammal. Sea otter mortality in fish and shellfish traps: estimating potential impacts and exploring possible solutions. Biol. Killer appetites: Assessing the role of predators in ecological communities. Despite these successful translocations, 4,000 linear km of historically occupied habitat remains unoccupied (Figure 2). Predation has had a significant effect on some sea otter populations (see Question 7), especially in the Aleutian Islands (killer whales) and more recently in California (white sharks), although there is no evidence that the carcasses are consumed by white sharks (Tinker et al., 2016). In 2020, the Commission commented on more proposed revisions to the stock assessment report. These measures are essential because they are sensitive indicators of population and environmental change and provide insights into the mechanisms of change (e.g., distinguishing food resource limitation from the effects of physical disturbance, disease, or predation pressure). Organizations engaged in sea otter management and conservation will benefit from collaboratively designing sea otter monitoring protocols across the North Pacific that will optimize efforts, enable the detection of trends and causes, and provide for spatial contrasts of those variables over time (Coletti et al., 2016). Mamm. (2013). Foraging effort (i.e., number of hours per day spent feeding) appears to be related to the status of the population relative to food availability across nearly all the sea otters current range (Estes et al., 1986; Bodkin et al., 2007; Monson and Bowen, 2015; Coletti et al., 2016; Cortez et al., 2016). Sea otters are found almost everywhere in the world. With increased sea otter foraging effort, GWA has observed a decline in available clam biomass further supporting food limitation as the driver in the sea otter population status. This abundant population lasted until the early 1700s when the hunting of otters for their pelts began to popularize. Sea otters can see clearly above and below the water and have good senses of smell and hearing. Sci. 21, 169172. A. Analysis of 13 years of demographic and genetic data from 1,006 sea otters to assess multiple effective population size estimators, as well as temporal trends in genetic diversity and population . Where sea otters persist, there is more complexity and productivity in the nearshore marine ecosystem. Why dont scientists kill sea urchins to help maintain the kelp population? Trend lines for the mainland (left vertical axis) are shown as 3-year running averages of independents (dashed green line) and total otters (solid blue line). (1995). Sci. (1988). Image by R. Davis taken under the authority of United States Fish and Wildlife Service LOC MA-043219. A raft usually comprises single-sex sea otters numbering from 10 to over one hundred individuals. doi: 10.1038/nclimate2763, Atwood, T. B., and Hammill, E. (2018). While goals may vary, either survey type can generate population trend data, and it is important that accepted protocols be followed consistently to allow comparisons over space and time. Within that range, sea otters exist along the exposed coasts of many island groups, particularly in the western Aleutians, at extremely low densities (e.g., only one sea otter was sighted at the Ogliuga/Skagul Island group in the 2015 skiff survey; USFWS). Prog. Prey choice and habitat use drive sea otter pathogen exposure in a resource-limited coastal system. Look in the library and on the Internet to learn what animals live in a kelp forest. A., and White, C. M. (1975). Setting realistic recovery targets for interacting endangered species. (1978). The USGS range-wide sea otter census has been undertaken each year since 1982, using consistent methodology involving both ground-based and aerial-based counts. doi: 10.2307/1380163. The spread of a reinvading species range expansion in the California sea otter. This article was a collaborative effort by all authors. Draft Periodic Status Review for the Sea Otter in Washington. /ColorSpace /DeviceRGB The guard hairs can be brown to black to silver. 71, 20342044. Life history plasticity and population regulation in sea otters. Estimating recreation and existence values of sea otter expansion in California using benefit transfer. The goal of this article is to identify and address some of the key questions and challenges for future research and management that will contribute to the full recovery of sea otters to pre-exploitation levels, reoccupation of their historical range, and restoration of nearshore ecosystems. A second method to monitor abundance is to correct for sighting bias of animals not detected and areas not surveyed. ZM' NXd$t S4jBc 35*([3mS?AT?23n VTFloB'@{#"Q#9tf(;l&~Y]r]BRILI=RaqoFHlVq3_b#=:#$Cqh5Ig!HHX@7;f(ZAM":kbSv()452.%XbCMb0~M{*!*={YQG0p Specifically, as sea otters reoccupy habitat, they drive a cascade of ecological effects including a reduction in the abundance of herbivorous (primarily kelp eating) macro-invertebrates such as sea urchins, thereby restoring canopy-forming kelp (Estes, 2015; see Questions 2 and 3). Sea otters may homogenize mussel-beds and reduce habitat provisioning in a rocky intertidal ecosystem. However, available information is often inadequate for managers to conduct meaningful analyses or to anticipate and mitigate conflicts before they occur. Plot of southern sea otter population trends along the mainland coast of California and at San Nicolas Island over the period 19902013. Foraging data were collected on a total of 2,675 foraging dives in 167 foraging bouts, and the majority of identified prey on successful dives (n=1,335) were sea urchins (940) followed by snails (240) and crabs (78). A lock () or https:// means youve safely connected to the .gov website. As a result of the failure finding, there no longer is a legal obligation to try to prevent expansion of the parent populations range south of Point Conception. We used precision estimates and conducted simulation analyses to assess the power of detecting 10-percent or greater decreases in population growth rates and how this power is likely to change with years of observation, survey effort, and the size of decrease. In areas occupied by younger or non-territorial males, food may be the primary factor driving density and emigration to unoccupied areas. To achieve this, we will work with multiple collaborators to conduct a multi-disciplinary investigation of sea otter ecology, health and population biology. Given that southern sea otters have failed to significantly expand their range over the past two decades and the recent decline in the population trajectory, the Commission also recommended that the FWS make its stock assessment reviews available annually. Our poor understanding of sea otter movements results from the inability to use satellite telemetry. %&'()*456789:CDEFGHIJSTUVWXYZcdefghijstuvwxyz (1947). As sea otters reoccupy northern Japan for the first time in over one hundred years, local fishing communities that harvest high-value invertebrates (e.g., uni sea urchin roe sells for $300 kg, and a sea otter can eat 45 kg per day) may place pressure on the government to limit the extent of their reoccupation. Indirect effects and prey behavior mediate interactions between an endangered prey and recovering predator. A., Hatfield, B. Bednykh, A. M., Burkanov, V. N., Kornev, S. I., and Krivolapov, I. I. Mar. ELKHORN SLOUGH SEA OTTER RESEARCH - OF ESTUARIES AND SEA OTTERS. Incorporating diverse data and realistic complexity into demographic estimation procedures for sea otters. Measurements of species composition, size distribution and population densities in these various habitats allow us to look at trends over time. They can swim on their backs easily, and their muscular tail helps them steer and swim. << doi: 10.7589/0090-3558-39.3.495, Krkosek, M., Lauzon-Guay, J. S., and Lewis, M. A. Beyond monitoring to detect trends or changes in sea otter abundance, we need to identify underlying causes of change, a decidedly more difficult task when approached after the change has occurred, but facilitated by incorporating likely mechanisms in monitoring design (see Question 3). Between 1911, when hunting was prohibited, and 1972, when the MMPA was passed, these otters recolonized more than 200 miles (370 kilometers) of the California coast. Because demand for sea otter artifacts is small, the number of animals killed yearly is modest but increasing [currently averaging more than 1,000 per year in Alaska (USFWS, Anchorage, AK, United States)]. History and status of translocated sea otter populations in North America. Sea otters and kelp forests in Alaska generality and variation in a community ecological paradigm. M.S. Potential designations could be based on both demography and habitat characteristics that currently allow sea otter persistence in some locations (see Questions 5 and 7), and could consider rates of genetic exchange between subpopulations, with the goal of maintaining or even improving the genetic health and heterozygosity of subpopulations (see Question 5). Dis. Not ready to purchase a subscription? 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