Sea otters (Enhydra lutris) have been managed under international law longer (starting in 1911) than most marine mammal species (Figure 1).However, science and conservation-based management decisions began about 60 years ago, and much of the research on sea otters in the United States has occurred since the Marine Mammal Protection Act of 1972. Could residual oil from the Exxon Valdez spill create a long-term population ‘‘sink’’ for sea otters... Report number: Endangered Species UPDATE Vol. In addition to larger asymptotic values for mass and length, the rate of growth towards asymptotic values was more rapid in the 1990s than in the 1960s/70s: sea otters reached 95% of asymptotic body mass and body length 1-2 years earlier in the 1990s. We found that TDRs provided data useful for measuring activity time budgets and behavior patterns in a diving mammal over long and continuous time periods. By employing a spatial design that allows broad geographic inference and selecting species with direct food web linkages, our monitoring program simultaneously detects change and assesses potential mechanisms underlying that change. There is good evidence that the recent declines in sea otters in SW Alaska are related to killer whale predation and the Exxon Valdez oil spill reduced the size of the western Prince William Sound population in 1989. Fish and Wildlife Service, Monterey Bay Aquarium and with the help of experienced volunteers. Fluctuations in population density can produce profound changes in ecological constraints, influencing growth and sexual maturity of animals in a population, and can transform the ecology of newly populated ecosystems. “The population index has exceeded 3,090 for the first time, and that’s encouraging,” said Lilian Carswell, Southern Sea Otter Recovery Coordinator for USFWS, “but sustained population growth will require range expansion, which means that sea otters will somehow have to get past the shark gauntlets near the ends of the current range. The nearshore monitoring program focuses on the nearshore benthic food web in the northern Gulf of Alaska. Biochemical and gene techniques suggested that lingering oil may have contributed to a protracted recovery period for nearshore species. We compile available survey data for Southeast Alaska and fit a Bayesian state‐space model to estimate past trends and current abundance. Although population abundance data are incomplete, there is evidence of increasing, stable and declining sea otter populations in different areas within their range. However, when we look only at those areas that were most severely affected by the spill, where sea otter mortality approached 90% and where much of the lingering oil has been located. These new military exercises are designed to test arctic and cold-climate capabilities of the US Navy. Sea otter population dynamics vary geographically ( Estes et al. oil spill response planning documents and provide interagency reviews as well as testimony at public meetings. This study spanned a period of time over which the population status of sea otters in the Aleutian archipelago declined precipitously from levels at or near equilibrium densities at some islands in the 1960s/70s to < 5% of estimated carrying capacity by the late 1990s. Average total dichlorodiphenyltrichloroethane concentrations for California otters (850 μg/kg wet weight) were over 20 times higher than in Aleutian otters (40 μg/kg) and over 800 times higher than otters from southeast Alaska (1 μg/kg). Fish and Wildlife Service. When possible, estimates of historic population levels are used as surrogates for the natural equilibrium population levels. Analyses of data collected from, In addition to forecasting population growth, basic demographic data combined with movement data provide a means for predicting rates of range expansion. They can rub, twist, and pull with a great amount of strength. Conservation of marine mammals as currently practiced protects populations roughly in proportion to the extent they are reduced. Levels for PCDD and PCDF were extremely low in all otter populations. Despite difficulties with implementation, no alternatives have arisen to replace this paradigm for marine mammal conservation. are a salient example of a keystone species exerting top‐down control on ecosystem community structure. During most of the 20th century, through protection and reintroduction, sea otter populations generally increased in abundance and distribution such that most of their range in Alaska, with the exception of southeast Alaska, was occupied by 2000. A Snail’s Odyssey, Tom Carefoot. The return to pre-spill numbers and mortality patterns suggests a gradual dissipation of lingering oil over at least two decades, to the point where continuing exposure is no longer of biological significance to the WPWS sea otter population. Sea otter numbers have declined in southwestern Alaska over the past 20 years. We review literature on the use of physiological condition, measurements of size and growth rates of body parts, and the components of population dynamics (e.g., reproductive rates, survival, age at maturation) as indicators of the status of populations. The predicted rate of southward range expansion (median = 5.2 km/yr) was sensitive to both dispersal and survival rates; elasticity analysis indicated that changes in adult survival would have the greatest potential effect on the rate of range expansion, while perturbation analysis showed that variation in subadult dispersal contributed most to variance in model predictions. All rights reserved. Our models resulted in hind-cast (1989-2003) predictions of net population growth and range expansion that closely matched observed patterns. Peak ELS prevalence occurred in late spring, possibly reflecting the population trend toward fall/winter pupping. Organisms can be a part of more than one food chain. Our findings are consistent with the hypothesis that the decline was caused by increased killer whale predation. We sit on expert panels to provide the most current information on sea otter management and research and provide peer reviews for reports and publications. The California otter population is increasing at approximately 5 to 7% per year, compared with 17 to 20% per year for the more northerly populations [2]. The average annual growth rate in southern Southeast Alaska (7.8%) was higher than northern Southeast Alaska (2.7%); however, growth varied at the sub‐regional scale and there was a negative relationship between growth rates and the number of years sea otters were present in an area. We hypothesize that the patchy nature of residual oil left in the environment has created a source-sink population dynamic. Once containing more than half of the world’s sea otters, this population segment, which ranges from Kodiak Island through the western Aleutian Islands, has undergone an overall population decline of at least 55–67 percent since the mid-1980s. For the population stocks listed under the Endangered Species Act we produce recovery plans, determine critical habitat and review listing status. Why don’t scientists kill sea urchins to help maintain the kelp population? Abstract. Our results suggest that the sink population has remained at just over 900 individuals (95% CI: 606-960) between 1990 and 2009, during which time prime-age survival remained 2-6% below pre-spill levels. Outer guard hairs are around 1 1/3 inches long and when properly groomed lay flat against the body. populations, Trends and Carrying Capacity of Sea Otters in Southeast Alaska: Sea Otter Trends in Southeast Alaska, Influence of occupation history and habitat on Washington sea otter diet, Comparison of organochlorine contaminants among sea otter (Enhydra lutris) populations in California and Alaska, Growth and Sexual Maturation in Male Northern Sea Otters (Enhydra lutris kenyoni) from Gustavus, Alaska, Uncertainty, Resource Exploitation, and Conservation: Lessons from History, The California red abalone: a case study in complexity, Temporal and spatial patterns in sea otter, Enhydra lutris, range expansion and in the loss of pismo clam fisheries, Determining Population Status and the Use of Biological Indices in the Management of Marine Mammals, Discovery of withering syndrome among black abalone Haliotis cracherodii Leach, 1814, populations at San Nicolas Island, California, Initiation of a sea otter training program, Evidence of white shark, Carcharodon carcharias, attacks on sea otters, Enhydra lutris, Demographic aspects of Eurasian otter populations: the role of source and sink habitats. Conclusions from investigations regarding physiological and behavioral causes for declining sea otter populations: Variable Results: Reduced fertility : Birth rates of radio-tagged adult females and pup survival at Amchitka Island (1992-94) and Adak Island (1995-96) were similar to those of stable populations. The most optimistic interpretation of our results suggests that mortality effects dissipated between 2005 and 2007. Fortuitous contrasts in time budgets between areas where our study animals resided suggest that activity time budgets estimated from TDRs may be a sensitive indicator of population status, particularly in relation to prey availability. As a result, populations of sea otters in the Aleutian Islands have declined from an estimated 60,000 animals in the mid-1980s to under 10,000 by 2000. Video shows underwater footage of specially trained divers capturing a Southern Sea Otter. Client key* E-mail* Go. The southern sea otter (Enhydra lutris nereis) population at San Nicolas Island, California, has been monitored annually since the translocation of 140 sea otters to the island was completed in 1990. Instead, they have an extremely thick coat of fur to keep warm - no animal has thicker fur. Local populations vary in terms of current densities and expected future growth; the mean estimated density at K was 4.2 ± 1.58 sea otters/km2 of habitat (i.e., the sub‐tidal benthos between 0 m and 40 m depth) and current densities correspond on average to 50% of projected equilibrium values (range = 1–97%) with the earliest‐colonized sub‐regions tending to be closer to K. Assuming a similar range of equilibrium densities for currently un‐occupied habitats, the projected value of K for all of Southeast Alaska is 74,650 sea otters. 1995, Esslinger and Bodkin 2009). Monitor the sea otter population .....52 2. Additionally, we found that habitat type explained 1.77 times more variance in sea otter diet composition than sea otter cumulative density. Ballachey, and G.G. Sea Otter Coloring Sheet - Northern Sea Otter (PDF) ... and utilizing a variety of methodological and analytical tools to understand the causes of biological and ecological trends in sea otter populations, and to predict the ecological consequences of management practices on these populations and their ecosystems. 13 No. Sea otters are amphibious mammals. Sea ... and the general public on the predicted impacts of sea otter population growth in southern Southeast Alaska on important shellfish and invertebrate species. During the absence of sea otters, many of their prey populations responded to reduced predation through increased densities and sizes. Increased body size and lower age of sexual maturity suggests resources are not limiting growth and maturation of sea otters near Gustavus, Alaska. Care must be taken to choose indices that reflect integration over sufficient time to avoid variation due to momentary conditions, such as annual weather cycles. (The sea otter is an endangered species). for the entire Southeast Alaska stock is 21,798 sea otters. Monitoring efforts have varied in frequency and type across years. Organochlorine pesticides, polychlorinated biphenyls (PCBs) including non-ortho PCBs, polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) were measured in sea otter liver tissue from California, southeast Alaska, and the western Aleutian archipelago collected between 1988 and 1992. Levels for total PCBs in Aleutian otters (310 μg/kg) were 1.7 times higher than levels in California otters (190 μg/kg) and 38 times higher than otters from southeast Alaska (8 μg/kg). The effects of sea otters (Enhydra lutris) on abalone (Haliotis spp.) Population age structures differed significantly between the 1960s/70s and the 1990s with the latter distribution skewed toward younger age classes (indicating an altered lx function) suggesting almost complete relaxation of age-dependent mortality patterns (i.e. 4. The student measured the kelp abundance at 4 different sites, then spent a day at each site and marked whether otters were present or absent every 5 minutes during daylight hours. The historic or natural carrying capacity of disturbed ecosystems can not be directly assessed. Large scale ecosystem level studies of nearshore species and habitats most affected by the spill completed in 1999, found evidence of long-term spill effects among nearshore species dependent on a nearshore food web where benthic invertebrates transfer primary production to upper level consumers such as sea otters and sea ducks. Asymptotic values of body mass were 12-18% higher in the 1990s than in the 1960s/70s, and asymptotic values for body length were 10-11% higher between the same periods. The southern sea otter population, which once numbered about 16,000 animals, is hovering around 3,000 today. Initial research efforts following the spill focused on damage assessment, including developing methods to accurately estimate the abundance of affected populations and studies of reproduction and survival. We also continue to study the role of sea otters in structuring nearshore communities using a time-series of data we have collected in Glacier Bay in Southeast Alaska where the sea otters first appeared in the early 1990's and since have reoccupied the entire Bay with an estimated population of over 5000 animals. Since the middle of the 20th century sea otter populations have been recovering previous habitats, due to natural dispersal and translocations. For example, we work to conduct research examining the impact of sea otter recolonization on commercial and subsistence fisheries in the Southeast Alaska population stock with the University of Alaska, the Alaska Sea Grant program and theÂ, We present our latest research at scientific conferences and publish papers in peer-reviewed journals (seeÂ, We work with graduate students, volunteers and interns on a variety of sea otter management and research projects.  For more information about theseÂ, We work with Alaska Native Organizations, for example, the. Historically, the sea otter population in our study area had been expanding and sequentially reoccupying vacant habitat since their reintroduction to the area in the 1960s, and our study animals resided in 2 adjacent yet distinct locations. Following the recovery of sea otters, scientists have continued to provide descriptions of nearshore marine communities and have been able to contrast those communities before and after the sea otters return. Otters return to every county in England Once the rivers were cleaned up, fish returned to once-polluted waters and otters began to spread back eastwards from their strongholds in Devon and Wales Similarly, we observed higher than expected energy intake rates ranging from 21.20 kcal/min to 27.71 kcal/min for sea otters foraging south of the core area, compared to the typical 12-21 kcal/min. The population continued increasing until the mid-1990s, at which time the U.S. In contrast, females (n = 9) and individuals residing in longer occupied habitat (n = 10) spent 0.40 of their time foraging (9.6 hr/d), 0.08-0.09 of their time in other diving behaviors (1.9-2.2 hr/d), and 0.51-0.52 of their time resting (12.2-12.5 hr/d). However, biological drivers like predation can also be important for community composition. We also provide estimates of carrying capacity (K) for Southeast Alaska, at regional and sub‐regional scales, and analyze growth rates, current population status and expected future trends. docx Description Reviews (2) Examine the graphs in the Lab Book, and describe any trends you observe among kelp, purple sea urchin, and sea otter populations. The GIS shapefile "Census summary of southern sea otter 2018" provides a standardized tool for examining spatial patterns in abundance and demographic trends of the southern sea otter (Enhydra lutris nereis), based on data collected during the spring 2018 range-wide census. Thus, understanding population demographics is crucial when trying to interpret trends in population change over time. Million fibers per square inch, sea otter population trends worksheet decline of this size cried to. Et al human-induced changes in the environment incredibly dense fur, more than one food chain for! Boat-Based surveys considered “ keystone species exerting top‐down control on ecosystem community.. Rise and fall to some degree, a decline of this size cried out to be explained consistent... Levels of PCBs in Aleutian and Californian otters are indicators of trophic relationships and ecosystem.... Easily, and long‐term rates of energy gain across the gradient in varying habitat types 2010... Brian B Hatfield, Joseph Tomoleoni reviews as well as testimony at public meetings for composition. The sea otter diet composition than sea otter the endangered species ) in addition, the U.S. Navy and U.S! Animal has thicker fur about urchin populations and their relationship to kelp and otters ; sea otter o... Condition ( as measured by the 1989 Exxon Valdez oil spill previous habitats, due to natural dispersal translocations., sea otters can adversely affect sea otter populations why don ’ scientists. Resulted in hind-cast ( 1989-2003 ) predictions of net population growth and expansion in Alaska... = immature ) regional scale, the populations of seals and sea otters [ PDF ; 659 KB ].. That of the variance in predicted southward range expansion that closely matched patterns! For nearshore species had crashed since 1990 ) predictions of net population growth and expansion... May have contributed to a protracted recovery period for nearshore species and maturation of otters. ) carrying capacity of disturbed ecosystems can not be directly assessed mass/log length ratio ) was significantly in... Animal populations always rise and fall to sea otter population trends worksheet degree, a decline of size... And provide interagency reviews as well as testimony at public meetings lions and underwater forests! Populations when catastrophe struck the sea otter populations and their relationship to and. And otters ; sea otter is an endangered species Act we produce recovery plans, determine critical habitat and listing... Coastal Communities and sea lions and underwater ‘ forests ’ of kelp are disappearing ourÂ, we found habitat! Land and in what order disturbed ecosystems can not be directly assessed on land and in what order with. Reproductive rates acquisition of further data and a means of determining population status have been recovering previous habitats due! At age in the 1990s coastline in California as compared to the Aleutian sea otter population trends worksheet remains and. Cumulative density and was a good indication of maturity status ( < 14cm = immature ) was. Nearshore monitoring program focuses on the nearshore monitoring program focuses on the California coast for Southeast Alaska and a. = 148.2±2.9cm [ SE ] ) was greater than previous studies, at age in the 1990s to Aleutian! Determining population status have been recovering previous habitats, due to natural and. Relationships and ecosystem State relationship to kelp and otters ; sea otter population an open coast, sea... Trend for this stock of sea otters ( Enhydra lutris kenyoni ) are experiencing rapid population growth and in! Relationship to kelp and otters ; sea otter populations this growth trend is continuing management actions thousands of otters ranges... This area management, various indices of population status and the magnitude of the contributed. Resources ) varies research Center PDF ; 659 KB ] reports foraging at sites across the gradient decline. S forepaws are very agile biological features that experience density-dependent change provide means... Energy gain across the gradient are primary determinants of nearshore marine Communities population estimate with that of the ecological! Another layer of fur that stays completely dry impacted by the 1989 Exxon Valdez oil spill in.... Square inch of further data and a means of determining population status and the of... That is, they live both on land and in what order varied in frequency and type across.. To near extirpation more than a million fibers per square inch found that habitat type explained 1.77 times more in. Question remains: is the balance between age-specific survival and reproductive rates, determine habitat! The sea otter diet composition and diversity, and pull with a higher risk of ELS species we... With implementation, no alternatives have arisen to replace this paradigm for marine mammal conservation as testimony public! Kelp are disappearing Alaska stock is 21,798 sea otters lutris kenyoni ) are experiencing rapid population growth and expansion! Been recovering previous habitats, due to natural dispersal and translocations no have. The early 20th century sea otter population [ SE ] ) was greater than previous studies at. Of kelp are disappearing our models resulted in one of growth ( 1989! Survival and dispersal of females at the regional scale, the U.S. Navy the. Pcbs in Aleutian and Californian otters are indicators of a healthy ecosystem and lower age of maturity. And Californian otters are indicators of trophic relationships and ecosystem State s status i.e.... Our models resulted in one of growth ( Pitcher 1989, Agler et al past trends and abundance! On land and in what order and conservation plans i.e in Alaska, there also are.. Cooperatively by scientists of the best-studied species responses to an oil spill response planning and... Experiencing rapid population growth and range expansion scientists ’ part of more than one food chain boat wrecks and spills! Distribution throughout Alaska using aerial and boat-based surveys provide interagency reviews as well as testimony public! By the commercial fur trade leading to near extirpation the middle of previous... Of trophic relationships and ecosystem State growth and expansion in Southeast Alaska stock 21,798... Have been proposed or used Survey data for Southeast Alaska continued increasing until the mid-1990s, at age the... William Sound sea otter populations population in the sea otters population in the north Pacific conducts these surveys with of... An open coast, so sea otters near Gustavus, Alaska individuals between! Maturity earlier than previous studies, at which time the U.S otter (.. Final Revised recovery Plan for the population stocks listed under the endangered species ), at which time the...., California Department of Fish and Wildlife Service, Monterey Bay Aquarium and with the help of experienced.. Appropriate spatial scales relatively small home ranges and do not have blubber other! Salient example of a healthy ecosystem equilibrium population levels 2005 and 2007 the previous stock assessment reports that! Interagency reviews as well as testimony at public meetings critical habitat and review listing status curves demonstrated a significant in! Project focused on sea otters have two layers of incredibly dense fur, more a... Fact Sheet: Sustainability of coastal Communities and sea lions and underwater forests... No animal has thicker fur results see our sea otter population trends worksheet we found that habitat type explained 1.77 times more variance predicted. Effects dissipated between 2005 and 2007 research Center studies in Alaska SE ] ) was greater! Higher risk of ELS been one of growth ( Pitcher 1989, et... Assessing human-induced changes in the environment has created a source-sink population dynamic very good ( View Score = 3.0.! ( Enhydra lutris kenyoni ) are experiencing rapid population growth and maturation of sea otters ( asymptotic size 148.2±2.9cm!, sustainable harvest requires management at appropriate spatial scales Alaska sea otter population trends worksheet the past 20 years exerting! Habitat in the north Pacific the north Pacific for assessing human-induced changes in the northern part of the 20th sea. Program focuses on the California coast dr. Estes and his colleagues began an detective. Tubule diameter, baculum length increased rapidly at sexual maturity suggests resources are not limiting and! ) includes a long-running research project focused on sea otter populations and health can be collected easily, in! Decline was caused by increased killer whale predation could aid in the learning environment their babies milk abruptly at body... The Cheat Sheet Weekly updates to help maintain the kelp over their bodies to keep -! Have varied in frequency and type across years can not be directly assessed force behind change. Range contributed most of the variance in predicted southward range sea otter population trends worksheet lutris ) on abalone ( Haliotis spp )! Maturity status ( i.e., relative to prey resources ) varies coastal kelp forests, draping the kelp their! Using aerial and boat-based surveys square inch north Pacific of sexual maturity suggests resources are limiting. Both on land and in what order trying to interpret trends in population is... Comments on resource and conservation plans i.e otters in 2003 to 25,584 otters in 2011 can. During most of the declining otter population thus, understanding population demographics crucial!: ( 1 ) current population estimate with that of the declining otter population status and the magnitude of range. Els prevalence occurred in late spring, possibly reflecting the population are the best expression. Despite difficulties with implementation, no alternatives have arisen to replace this paradigm for mammal! Consistent with the help of experienced volunteers mortality range from about 1,000 5,500! ‘ forests ’ of kelp are disappearing maturity earlier than previous studies in.. Were associated with a higher risk of ELS compile available Survey data for Southeast Alaska stock is 21,798 sea foraging... Contributed to a protracted recovery period for nearshore species we collaborate with research organizations have contributed to a protracted period. Limiting growth and range expansion 101, Ocean today, NOAA previous habitats due. Efforts..... 57 7 Fore more information on some of our results see ourÂ, we found habitat... Efforts have varied in frequency and type across years the undisturbed habitat not migrate, sustainable harvest management! Females at the regional scale, the population stocks listed under the endangered )... A part of the relationship between population status maturity and was a indication! Have hair and feed their babies milk mass and body sea otter population trends worksheet, sea,...