sea otter population trends worksheet

sea otter population trends worksheet2020/09/28

The San Nicolas population remained small (20 animals) for decades, and the translocation program was administratively deemed a failure in the early 2000s (Federal Register 77, 2012; p. 75266). rents. Includes a craft for the story. We should reconsider the spatial scales on which we define sea otter populations in recognition of this biological reality. The findings and conclusions in this article are those of the author(s) and do not necessarily represent the views of the United States Fish and Wildlife Service. It is plausible that the few surviving females may not have access to a male during their short estrus periods (i.e., allee effects) at these extremely low densities. Listed as threatened under the Endangered Species Act and designated as depleted under the Marine Mammal Protection Act. Sea otters were presumed extinct in California after the 19th century fur trade years, but were rediscovered in the 1930s by the public, when as few as 50 animals were documented persisting in nearshore areas off the coast of Big Sur. (1988). Sci. Estimates of energy intake rates averaged 17.3 kilocalories per minute (95-percent confidence interval =15.619.0 kilocalories per minute) and suggest possible variations across years and seasons, but confidence intervals based on specific years of data were relatively wide. The average body mass for males is about 88 pounds, with a range of 49-99 pounds; females range from 31-73 pounds. B., Staedler, M. M., et al. (1986a). In 2017, the Commission commented onproposed revisions to the southern sea otter stock assessment report. 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). because of these species reliance on kelp or seagrass habitat during critical phases of their life history. Home Facts Privacy About Blog Contact Terms. He thereafter lingers in a coma for 2 months and then dies. 84, 5564. Why do you think sea otters have done better in Washington State than in other areas, such as Oregon and Northern Mexico, where the animals once lived? Open-File Report This strategy does come at the cost of reduced statistical power due to reduced sample sizes within specific subpopulations but adds strength to interpretations of change that occur within one or a few local subpopulations or across all populations (e.g., Coletti et al., 2016, also see Question 3). 5 0 obj Along the west coast of North America, they remained absent from eastern Prince William Sound in Alaska to central California- a linear distance of approximately 4,000 km of nearshore habitat where they formerly existed. Predation Ph.D. thesis, University of Alaska, Fairbanks. Sea otters reestablished in British Columbia. Sato, C. L. (2018). Here, we highlight an existing monitoring program, Gulf Watch Alaska (GWA), to illustrate how nearshore food web-based monitoring can indicate alternative causes of change related to sea otter recolonization on nearshore communities. That is, localized harvests limited sea otter impacts on local subsistence shellfish resources while not having a significant impact on the range-wide sea otter population. doi: 10.3354/meps082103, Kvitek, R. G., Oliver, J. S., DeGange, A. R., and Anderson, B. S. (1992). doi: 10.1046/j.1523-1739.1997.96109.x, Raimondi, P., Jurgens, L. J., and Tinker, M. T. (2015). Animal populations are limited by density-dependent and density-independent factors, many of which are known for sea otters, although the importance of individual factors varies. Created by. 1999). In the presence of sea otters, an important natural predator, abalone populations cannot recover to the densities and distribution that characterized the era when sea otters were ecologically extinct. Prog. >> doi: 10.1016/j.jas.2011.12.006, Tallis, H. (2009). Although the data from these earlier surveys provide reasonably detailed assessments of (1) trends in sea otter abundance and distribution at several index islands (Fig. Reproduction, preweaning survival, and survival of adult sea otters at Kodiak Island, Alaska. doi: 10.1007/s10021-013-9715-7. Here, we give examples of the challenges in defining sea otter populations and the consequences of managing populations at an inappropriate scale. Monson, D. H., and Bowen, L. (2015). 20% per year (USFWS 2013b, USGS unpublished data). However, there is a delay between the time when sea otters expand into an area and when commercial-scale harvesting of shellfish becomes inviable, the length of which is somewhat species-dependent. Identifying the factors that regulate a species population density can provide insight into why population density varies spatially and temporally and when a recovering population has reached carrying capacity. +(> Xi~PHa3sX#s-mCR*1rFY$Vz!`:_OV Imagine that you are applying for money to study sea otters. A raft usually comprises single-sex sea otters numbering from 10 to over one hundred individuals. doi: 10.1016/j.cimid.2015.03.002. The diet of sea otters in the KEJF includes a high proportion of intertidal mussels (58%), which have experienced a period of decline and subsequent recovery despite consistent site-specific settlement of small mussels over time (Coletti et al., 2016; Bodkin et al., 2018). /CA 1.0 Mamm. Following their near extirpation, there was little effort to monitor them because remnant populations were small, remote and in some cases unknown. 19, 198216. B., Harris, M. D., and Ames, J. Our goals were to provide a comprehensive picture of population trends and abundance estimates at dierent spatial scales and to estimate equilibrium densities of sea otter populations in Southeast Alaska, and how they vary over space, as a tool to help resource managers anticipate In Russia, sea otters have a conservation status that prohibits capture or hunting except by special license for science or display purposes (Nichol, 2015). 32, 9971006. In contrast, white shark predation has had population-level effects within the southern sea otters range (Tinker et al., 2016). The average adult sea otter must eat 20 to 30 percent of its body mass in food each day just to meet its energy requirements. As sea otters reoccupy an area, populations of epibenthic prey such as sea urchins, crabs and abalone generally decline first followed by infaunal species such as large bivalves, depending on habitat (Kvitek and Oliver, 1992; Kvitek et al., 1993). 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. Comp. . However, the overall sea otter population size in southwest Alaska has declined by more than 50% since the mid-1980s, and there is no . This biologist uses microwave radiation to save endangered species, Chemists have unlocked the secrets of long-lasting Roman concrete, Native Amazonians make rich soils and ancient people may have too, Sea life may suffer as plastic bits alter metals in water, Heres how to increase clean energy without harming wildlife, The next astronauts to walk the moon will be more diverse than the last, A powerful laser can control the paths that lightning takes, Using Science News Explores in the Classroom. doi: 10.1016/B978-0-12-801402-8.00001-9, Larson, S. E., Ralls, K., and Ernest, H. (2015). Coinciding with recent population growth, the sea otter distribution, which previously tended to concentrate on the west side, appears to have shifted toward an expansion of use in the north and especially greater seasonal use in the north and south during winter and spring. .0.50 0 20 40 60 80 100 Time, days A-55793 . For example, the 3-year average of total otters for 1998 is the average of the total counts for 1996, 1997, and 1998. The population never grew as expected and in 2012,the FWS declared the translocation a failure. Bodkin, J. L., Ballachey, B. E., Cronin, M. A., and Scribner, K. T. (1999). doi: 10.1890/14-0492.1, Mazzillo, F. F. M., Shapiro, K., and Silver, M. W. (2013). National Oceanic and Atmospheric Administration Technical Memorandum National Marine Fisheries Service NOAA-TM-NMFS-SWFC-108. Sea otters can survive their whole life without leaving the water, but some do rest on land for short periods. doi: 10.1890/08-0765.1, Williams, P. J., Hooten, M. B., Womble, J. N., Esslinger, G. G., and Bower, M. R. (2018). Patterns of mortality in southern sea otters (Anhydrates lutris nereis) from 19982001. The Commission recommended ways to improve the potential biological removal estimate. In addition to abundance, trends, distribution, and forage energy intake across seasons and years, these replicated surveys provide information on the precision of data achieved by quarterly survey effort. doi: 10.1038/nclimate1944, Atwood, T. B., Connolly, R. M., Ritchie, E. G., Lovelock, C. E., Heithaus, M. R., Hays, G. C., et al. (2015). U.S.A. 106, 22422247. Consequently, the frequency of large scale surveys in areas such as Southeast Alaska and the Aleutian Islands declined to decadal intervals. Previous samples were collected from widely dispersed locations and shared among studies, and they suggested that sampling on a microgeographic scale should be considered in future genetic analysis. At the largest, the range spanned the entire northern Pacific Rim from Southern California to areas of Japan. Geographic variation in sea otters, Enhydra lutris. Sea otters have a high metabolism. doi: 10.1016/j.jembe.2015.05.020, Costa, D. P., and Kooyman, G. L. (1984). Wendell, F. (1994). doi: 10.2307/3800973. Following the modern discovery of sea otters in the North Pacific Ocean by Vitus Bering during his expedition in the mid-1700s, the maritime fur trade in the late 18th and 19th centuries reduced sea otter populations to less than 2,000 individuals combined. However, while sea otters are an important predator in the nearshore, they are not always the top predator and may become prey for higher-level predators. (2006). doi: 10.1073/pnas.94.26.14530, Miller, M. A., Gardner, I. Sea otters once numbered 300,000 and ranged around the North Pacific Rim from northern Japan through Russia, Alaska, Canada, and along the coast of the contiguous United States to central Baja California in Mexico (Figure 2). 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. 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). More information doi: 10.1016/j.mambio.2012.03.002, Yeates, L. C., Williams, T. M., and Fink, T. L. (2007). Continued research to allow full, pre-exploitation recovery and restoration of nearshore ecosystems should focus on at least seven key challenges: (1) Defining sea otter . 1 2 . /ColorSpace /DeviceRGB Sea otters do well in captivity and can be found in many. Trends in Sea Otter Population Abundance in Western Prince William Sound, Alaska: Progress Toward Recovery Following the 1989 Exxon Valdez Oil Spill . Initially, remnant populations were small and occupied small ranges, enabling surveys that could be conducted from skiffs with limited personnel and time. Chads et al. B., Eby, R., Van Dyke, E., Tinker, M. T., Marks, C. I., Johnson, K. S., et al. Ecol. Sacramento CA: Marine Resources Branch. The females raise their young without any assistance from the males. This partnership of federal, state and local institutions is seeking to increase our understanding of estuary habitat use by sea otters and to help inform the conservation and restoration of suitable habitat and water quality conditions at Elkhorn Slough. These intertidal sites span a range of habitats, from sheltered rocky areas to mussel beds to protected mixed-sediment beaches (Dean and Bodkin, 2011; Bodkin et al., 2016; Weitzman et al., 2017). The first is considered a census, where it is assumed that all animals in an area are counted, and precision is not usually estimated. obs.). Given the contribution of translocations to the conservation of sea otters by increasing the total numbers of sea otters present today, increasing population connectivity, increasing genetic diversity, and restoring coastal marine ecosystems, we suggest additional translocations be considered to facilitate sea otters recolonization of their historical range. (Theresa Soley/KTOO) John Ryan lives in Hollis, on Prince of Wales Island. As sea otter populations continue to expand in their range and numbers, monitoring will become increasingly challenging, likely resulting in reduced effort and statistical power to detect change (Williams et al., 2018). What would you do? These aquatic mammals are members of the weasel family are often seen floating on their backs. 50, 626637. 2) As the otters declined, urchin abundance increased because they had been released from predation. Figure 1 Open in figure viewer PowerPoint B., Ralls, K., and Ames, J. Their fur contains up to 1,000,000 hair follicles per square inch. As a result, the prey of the urchins - the kelp - vastly decreased in density because there were more urchins eating more kelp. And Fink, T. M., Shapiro, K., and survival of sea. Population Abundance in Western Prince William Sound, Alaska days A-55793, P. and... Ryan lives in Hollis, on Prince of Wales Island declined, urchin Abundance increased because they had released! L. J., and Ames, J such as Southeast Alaska and the consequences of managing at! Usually comprises single-sex sea otters ( Anhydrates lutris nereis ) from 19982001 doi: 10.1016/j.mambio.2012.03.002, Yeates L.!: 10.1890/14-0492.1, Mazzillo, F. F. M., and Tinker, M. M. and! 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