2. 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. survey of the sea otter population at San Nicolas Island was completed earlier (April 15–18). The historic or natural carrying capacity of disturbed ecosystems can not be directly assessed. 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. Future analyses can improve upon the precision of K estimates by employing more frequent surveys at index sites and incorporating environmental covariates into the process model to generate more accurate, location‐specific estimates of equilibrium density. 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. The USGS spring range-wide sea otter census has been undertaken each year since 1982, using consistent … Ogden A (1933) Russian sea otter and seal hunting on the California coast. This Shape file includes a series of summary statistics derived from the raw census data, including sea otter density (otters per square km of habitat), linear density (otters per km of coastline), relative pup abundance (ratio of pups to independent animals) and 5-year population trend (calculated as exponential rate of change). Our approach provides guidance for the acquisition of further data and a means of forecasting the consequence of specific management actions. 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. The sea otter’s forepaws are very agile. 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, Monterey Bay Aquarium and with the help of experienced volunteers. Although wild animal populations always rise and fall to some degree, a decline of this size cried out to be explained. 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. 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.Â For more information about theseÂ, We work with Alaska Native Organizations, for example, the. As mammals, sea otters have hair and feed their babies milk. This article outlines a study that suggests that thriving sea otter populations keep sea urchins in check, which in turn allow kelp forests to prosper. 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. Kuluk Bay is on an open coast, so sea otters there are exposed to killer whales. Monitor the sea otter population .....52 2. Why don’t scientists kill sea urchins to help maintain the kelp population? nereis) as a case study, we utilized integro-difference equations in combination with a stage-structured projection matrix that incorporated spatial variation in dispersal and demography to make forecasts of population recovery and range recolonization. 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. Consistent with these differences, sea otters residing in more recently occupied habitat captured more and larger clams (Saxidomus spp., Protothaca spp., Macoma spp., Mya spp., Clinocardium spp.) Variation in survival and dispersal of females at the south end of the range contributed most of the variance in predicted southward range expansion. those typical of food-limited populations). 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. Sea otter populations in Southeast Alaska, USA, have increased dramatically from just over 400 translocated animals in the late 1960s to >8,000 by 2003. • Sea Otter Research o Sea otters are indicators of a healthy ecosystem. Which populations were wiped out, and in what order? At puberty, mean seminiferous tubule diameter, baculum length, and testes mass increased abruptly at 130cm body length. That is, they live both on land and in the sea. Â Fore more information on some of our results see ourÂ, We collaborate with research organizations. Thus, understanding population demographics is crucial when trying to interpret trends in population change over time. Growth curves were constructed for each of two main year groups: 1967-71 when the population was at or near carrying capacity and 1992-97 when the population was in steep decline. A Snail’s Odyssey, Tom Carefoot. We provide comments on resource and conservation plans i.e. 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. 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. Body condition (as measured by the log mass/log length ratio) was significantly greater in males than in females. We respond to pollution events, such as boat wrecks and oil spills that may threaten sea otters. 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. We detected significant differences in activity budgets among individuals and between groups within our sample. 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. Scientists with, 1. Why isn’t the sea otter population now growing as fast as it once was … Instead, they have an extremely thick coat of fur to keep warm - no animal has thicker fur. For the population stocks listed under the Endangered Species Act we produce recovery plans, determine critical habitat and review listing status. Subsequent research has resulted in one of the best-studied species responses to an oil spill in history. 3. The translocation and subsequent population growth and range expansion of the northern sea otter (Enhydra lutris kenyoni) in Washington State over the last five decades has created a spatio‐temporal gradient in sea otter occupation time and density, and acts as a natural experiment to quantify how sea otter population status and habitat type influence sea otter diet. Additionally, we found that habitat type explained 1.77 times more variance in sea otter diet composition than sea otter cumulative density. oil and gas exploration in Cook Inlet) to make sure development is not in violation of the Marine Mammal Protection Act and the Endangered Species Act.Â We review applications forÂ, We conduct outreach and education about sea otters, their conservation, and the Marine Mammal Protection Act at many different venues i.e. Research based on the diving behavior of sea otters in the intertidal and published oil encounter rates, indicates that all sea otters in those heavily oiled areas were likely to encounter Exxon Valdez oil at least annually and some as often as weekly into at least the early 2000's. The … Organisms can be a part of more than one food chain. Following a review of the history, utility, and potential of indirect methods for population assessment, we suggest that characteristics of populations, and the individuals within, give a better assessment of ecosystem conditions and relationships than can be achieved through direct measurement. Growth curves demonstrated a significant increase in body mass and body length at age in the 1990s. By 2009 our estimate of sea otter abundance in the western Sound was nearly 2,000 animals more than our first post spill estimate in 1993 of about 2,000 individuals. We fit models using the age distributions of both living and dying animals and estimates of sea otter population size to predict the number of sea otters in the hypothesized sink population and the number lost to this sink due to chronic exposure to residual oil. In wildlife management, various indices of population status have been proposed or used. 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. schools, special events, Tribal and community meetings. Growth models for body mass and length were fitted to data collected from 1842 sea otters Enhydra lutris shot or live-captured throughout south-west Alaska between 1967 and 2004. Long term continuation of studies investigating mortality from the annual collections of beach cast sea otter carcasses implicates elevated mortality as the factor contributing to delayed recovery, and suggests that chronic mortality after the spill meet or exceeded the acute mortality experienced after the spill. During most of the early 20th century sea otters were absent from large portions of their habitat in the north Pacific. The nearshore ecosys, Sea otters were severely impacted by the 1989 Exxon Valdez oil spill. Baculum length increased rapidly at sexual maturity and was a good indication of maturity status (< 14cm = immature). Further, source-sink population dynamics can explain the slow recovery observed in the spill-affected western Prince William Sound sea otter population and are consistent with available data. Northern sea otters (Enhydra lutris kenyoni) are experiencing rapid population growth and expansion in Southeast Alaska. These new military exercises are designed to test arctic and cold-climate capabilities of the US Navy. Increasing age and number of pregnancies were associated with a higher risk of ELS. Comparing the current population estimate with that of the previous stock assessment reports suggests that this growth trend is continuing. Studies in Avian Biology 15:119 – 133. Introduction. Using demography and movement behavior to predict range expansion of the Southern Sea Otter, Activity Budgets Derived From Time‐Depth Recorders in a Diving Mammal. Objectives of our sea otter population assessment studies include: 1) develop and test methods to identify the degree of population structuring among north Pacific sea otter populations, 2) develop and test techniques to accurately and precisely estimate the status of sea otter populations, 3) develop and test methods to identify cause(s) of change in the status and numeric trends of sea otter populations, 4) develop and test methods to determine the role of density dependent processes in affecting change in sea otter populations, and 5) evaluate the effects of population reductions and translocations on sea otter genetic variability. During the absence of sea otters, many of their prey populations responded to reduced predation through increased densities and sizes. © 2008-2021 ResearchGate GmbH. In particular, measures of biological features that experience density-dependent change provide indirect means of determining population status. The results of this study indicate an improved overall health of sea otters over the period of decline and suggest that limited nutritional resources were not the cause of the observed reduced population abundance. that the sea otter population in the Aleutian Islands of Alaska had crashed since 1990. Our models resulted in hind-cast (1989-2003) predictions of net population growth and range expansion that closely matched observed patterns. Current Population Trend The trend for this stock of sea otters has generally been one of growth (Pitcher 1989, Agler et al. Behavior. Monitoring efforts have varied in frequency and type across years. 38. Our results suggest that residual oil can affect wildlife populations on time scales much longer than previously believed and that cumulative chronic effects can be as significant as acute effects. 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. Sea otters have two layers of incredibly dense fur, more than a million fibers per square inch. At the time of the spill, the sea otter (Enhydra lutris) population inhabiting the spill area suffered substantial acute injuries and loss. The southern sea otter population, which once numbered about 16,000 animals, is hovering around 3,000 today. Fish and Wildlife Service 2003), three-year running averages are used to characterize population trends to dampen the effects of anomalous counts in any given year. Peak ELS prevalence occurred in late spring, possibly reflecting the population trend toward fall/winter pupping. Estimates of acute spill related mortality range from about 1,000 to 5,500 in the first months after the spill. Client key* E-mail* Go. Our current understanding of the dynamics of the southern sea otter population is largely based on MMS-funded studies conducted during the 1980s (Siniff and Ralls, 1988), at a time when the population was increasing. Sea otter numbers have declined in southwestern Alaska over the past 20 years. nter_objects) includes a long-running research project focused on sea otters. Although population abundance data are incomplete, there is evidence of increasing, stable and declining sea otter populations in different areas within their range. From the TDRs we constructed a continuous record of behavior for each, Over 20 years ago, the Exxon Valdez oil tanker spilled 42 million L of crude oil into the waters of Prince William Sound, Alaska, USA. The overall average activity budget (proportion of 24-hr/d) was 0.37 foraging (8.9 hr/d), 0.11 in other diving (2.6 hr/d), and 0.52 nondiving time (12.5 hr/d). 12, Affiliation: U.S. 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. They often rest in coastal kelp forests, draping the kelp over their bodies to keep from drifting away. Could residual oil from the Exxon Valdez spill create a long-term population ‘‘sink’’ for sea otters... Report number: Endangered Species UPDATE Vol. 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 All content in this area was uploaded by Daniel H Monson on Feb 02, 2018, ... Sea otter population dynamics vary geographically (, ... From 1983From to 1994, spring survey results indicated that the population was increasing about 5-6% per year. In addition, the populations of seals and sea lions and underwater ‘forests’ of kelp are disappearing. The source of PCBs to the Aleutian Islands remains unclear and vital to understanding the potential impacts to sea otters. “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. 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. 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. Implementation of this approach is fraught with practical problems: population levels are difficult and costly to estimate and current carrying capacity is essentially impossible to measure through environmental assessment. 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). 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. for the entire Southeast Alaska stock is 21,798 sea otters. 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. 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. Video shows underwater footage of specially trained divers capturing a Southern Sea Otter. Established in 1964, the IUCN Red List of Threatened Species has evolved to become the world’s most comprehensive information source on the global conservation status of animal, fungi and plant species. USFWS/Lisa hupp, Sea Otters and the Endangered Species Act, Skiff Operation Guidance to Avoid Disturbing Sea Otters, Serviceâs Division of Management Authority, The Southern Southeast Alaska Sea Otter Project, Fish and Wildlife Service, Region 8, sea otter program, U.S. Geological Survey Alaska Biological Science Center, California Department of Fish and Wildlife, sea otter necropsy program, Marine Mammal Research Unit, University of BC, Canada, Wildlife Health Center, University of California, Davis, Fish of the Week! Esslinger. In Alaska, there are areas that sea otters can expand into. Using the southern sea otter (Enhydra lutris, We describe a method to convert continuously collected time-depth data from archival time-depth recorders (TDRs) into activity budgets for a benthic-foraging marine mammal. 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. The recovery of sea otters to ecosystems from which they had been absent has affected coastal food webs, including commercially important fisheries, and thus information on expected growth and equilibrium abundances can help inform resource management. the Alaska Science Center were among the first responders to the 1989 spill and continue work today to document the process of recovery form this spill and to better understand the effects future contamination events on sea otters and the nearshore ecosystems they occupy. 4. Since the middle of the 20th century sea otter populations have been recovering previous habitats, due to natural dispersal and translocations. They estimated the impact of killer whales on sea otter populations by comparing trends in population size and survival rates of individually marked otters between two adjacent locations on Adak Island: Clam Lagoon and Kuluk Bay. We quantified sea otter diet composition and diversity, and long‐term rates of energy gain across the gradient. More recently the theory as to why the sea otter population is not growing in California and is stagnant in its growth trend is the nature of the coastline in California. There was also an increasing trend from the 1960s/70s through 2004 despite much year-to-year variation. 1995, Esslinger and Bodkin 2009). They can rub, twist, and pull with a great amount of strength. Educators and Parents, Sign Up for The Cheat Sheet Weekly updates to help you use Science News for Students in the learning environment. Although this approach involves inherent problems, there also are advantages. We have a one-dimensional coastline in California as compared to the two-dimensional coastlines of much of Alaska. The factors that ultimately regulate sea otter population abundance are not completely understood, but can include predation, human harvest, food limitation, disease and catastrophic events such as oil spill. Knowledge of the relationship between population status and the magnitude of the biological feature is necessary. Increased body size and lower age of sexual maturity suggests resources are not limiting growth and maturation of sea otters near Gustavus, Alaska. animals caught during 2004, when the population density was very low, were precluded by a small sample size and consequently only examined incidentally to the main growth curves. However, the unaffected source population appears to be counterbalancing these losses, with the model indicating that the sea otter population increased from; 2150 individuals in 1990 to nearly 3000 in 2009. However, the sea otter population was designated as "recovered" by 2013 based primarily on demographic data, including (1) a return to estimated pre-spill abundance of sea otters at heavily oiled northern Knight Island, and (2) a return to pre-spill mortality patterns. Trends in Sea Otter Population Abundance in Western Prince William Sound, Alaska: Progress Toward Recovery Following the 1989 Exxon Valdez Oil Spill By J.L. Males (n = 5) and individuals residing in recently occupied habitat (n = 4) spent 0.28-0.30 of their time foraging (6.7-7.2 hr/d), 0.17-0.18 of their time in other diving behaviors (4.1-4.3 hr/d), and 0.53-0.54 of their time resting (12.7-13.0 hr/d). In 2017, the U.S. Navy and the U.S. 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. Population. A student studies feeding relationships among sea otter, sea urchins and the abundance of kelp. Often data can be collected easily, and they usually reflect current environmental conditions for assessing human-induced changes in the environment. Dr. Estes and his colleagues began an ecological detective hunt to uncover the cause of the declining otter population. We track sea otter population abundance, trends, and distribution throughout Alaska using aerial and boat-based surveys. and other prey, and intertidal clams were more abundant and larger in this area. The nearshore ecosystem is broadly recognized as highly susceptible and sensitive to a variety of both natural and human disturbances on a variety of temporal and spatial scales. We used data from 14 TDRs to estimate activity-specific time budgets in sea otters (Enhydra lutris) residing near Cross Sound, southeast Alaska, USA. The effects of sea otters (Enhydra lutris) on abalone (Haliotis spp.) Fact sheet: Sustainability of Coastal Communities and Sea Otters [PDF; 659 KB] Reports. Undertake research that will facilitate and enhance recovery efforts .....57 7. Underneath the guard hair is another layer of fur that stays completely dry. Human harvest of sea otters can adversely affect sea otter abundance, evidenced by the commercial fur trade leading to near extirpation. 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). ... Ainley DG, Sydeman WJ, Hatch S, Wilson U (1994) Seabird population trends along the west coast of North America: Causes and the extent of regional concordance. Levels for PCDD and PCDF were extremely low in all otter populations. This approach requires estimates of: (1) current population level, and (2) carrying capacity of the undisturbed habitat. We collected focal observations of sea otters foraging at sites across the gradient in varying habitat types between 2010 and 2017. Our model improves upon previous analyses by partitioning and quantifying sources of estimation error, accounting for over‐dispersion of aerial count data, and providing realistic measurements of uncertainty around point estimates of abundance at multiple spatial scales. 1996).Prior to 1990, sea otter populations in the west- em Aleutians, southeast Alaska, British Columbia, and … Here we fit time-varying population models to data for the sea otter population of western Prince William Sound to quantify the duration and extent of mortality effects from the spill. Abstract. All rights reserved. Sea otters are amphibious mammals. In this regard, some species serve as indicators of trophic relationships and ecosystem state. The fundamental force behind population change is the balance between age-specific survival and reproductive rates. This approach assumes that animals in the population are the best integrated expression of their environment. However, the, Join ResearchGate to discover and stay up-to-date with the latest research from leading experts in, Access scientific knowledge from anywhere. We hypothesize that the patchy nature of residual oil left in the environment has created a source-sink population dynamic. Data collected in 2004 suggest a continued increase in body size, with nearly all data points for mass and length falling significantly above the 1990s growth curves. The nearshore is also an important triple interface between air, land, and sea that provides linkages for transfer of water, nutrients, and species between watersheds and offshore habitats. Sea otters (Enhydra lutris ssp.) Following Section 117 of the Marine Mammal Protection Act, we produce periodic Stock Assessment Reports for sea otters.Â See ourÂ Reports tab belowÂ for information on stock assessments. For many species, demographic rates change as the population’s status (i.e., relative to prey resources) varies. 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. Animals in this study reached sexual maturity earlier than previous studies, at age 3–4 years. 13 No. food chains and web's worksheets, coral reef community coloring pages and ocean coral reef coloring page are three main things we want to present to you based on the. 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. 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 . 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. ] ) was significantly greater in males than in females are primary of. Pregnancies were associated with a higher risk of ELS in 2003 to 25,584 otters in 2011 greater in than... Schools, special events, Tribal and community meetings two-dimensional coastlines of of! A protracted recovery period for nearshore species and oil spills that may threaten sea otters can adversely sea! Nearshore marine Communities varying habitat types between 2010 and 2017 observations of sea otters can expand into species as! Consequence of specific management actions numbers have declined in southwestern Alaska over the past, but now thousands... Size cried out to be explained species serve as indicators of trophic relationships and ecosystem State 101... 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And do not migrate, sustainable harvest requires management at appropriate spatial scales important for community.... Current population trend toward fall/winter pupping: is the balance between age-specific survival and reproductive rates their bodies keep! In the first months after the spill still influencing the Prince William Sound sea otter 101, today! Endangered species Act we produce recovery plans, determine critical habitat and listing. For the population continued increasing until the mid-1990s, at age 3–4 years measures of features. Oil may have contributed to a protracted recovery period for nearshore species one of growth ( Pitcher,... Aleutian Islands remains unclear and vital to understanding the potential impacts to sea otters, trends and... T scientists kill sea urchins to help maintain the kelp population long‐term diet studies provide. Survival and reproductive rates condition ( as measured by the 1989 Exxon oil!
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