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(SP-781: t. 6; 1. 40'; b. 10'1"; dr. 3'6"; s. 10 k.; cpl. 6
a. 1 1-pdr., 1 mg.)
On 11 June 1917, soon after the United States entered World War I, Sea Otter, a wooden boat built during 1911 by Britt Brothers, Lynn Mass., was acquired by the Navy from Hugh L. Willoughby of Newport, R. I.; and placed in service the same day.
Sea Otter served as a supply vessel on the east coast of the United States until placed out of service at war's end. Struck from the Navy list on 7 November 1919 Sea Otter was sold on 16 January 1920 to Joseph Guild of Boston.
A Middle Pleistocene Sea Otter from Northern California and the Antiquity of Enhydra in the Pacific Basin
Extant sea otters (Enhydra lutris) are remarkably well understood in terms of behavior, ecology, and interactions with humans, but the evolutionary history of this charismatic marine mammal is limited owing to a fragmentary fossil record. Disagreements over the generic assignment of various fossil otter remains to members of the tribe Enhydrini, and limited geochronologic data for these records have impeded attempts to interpret the evolutionary biogeography of Enhydra. A well-preserved femur of Enhydra sp. from a middle Pleistocene horizon within the Merced Formation of northern California is the oldest record of Enhydra in the Pacific with robust geochronologic age control. Bracketing 87 Sr/ 86 Sr dates indicate an age of 620–670 ka. Reappraisal of the geochronologic age of various occurrences of Enhydrini indicate dispersal of Enhydra into the Pacific through the Bering Strait no earlier than the middle Pleistocene. Somewhat older early Pleistocene fossils of Enhydra from Alaska and England suggest an Arctic or North Atlantic origin of the Enhydra lineage.
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Sea Otter Coats
Sea otters are meticulously clean. After eating, they wash themselves in the ocean, cleaning their coat with their teeth and paws. They have good reason to take care of their coats—it helps them to remain waterproof and insulated against the cold. Sea otters have thick underfur that traps air to form an insulating layer against the chilly waters (they have no insulating fat). This coat is invaluable to otters, but it has worth to some humans as well.
Sea otters were hunted for their fur to the point of near extinction. Early in the 20th century only 1,000 to 2,000 animals remained. Today, sea otters are protected by law.
Habitat and Distribution
Unlike some marine mammals like whales that would die if they were on land for too long, sea otters can go up onto land to rest, groom, or nurse. However, they do spend most if not all of their lives in the water—Sea otters even give birth in the water.
Although there is just one species of sea otter, there are three subspecies:
- The Russian northern sea otter (Enhyrda lutris lutris), which lives in the Kuril Islands, Kamchatka Peninsula, and Commander Islands off Russia,
- The northern sea otter (Enhyrda lutris kenyoni), which lives from the Aleutian Islands off Alaska, down to Washington state, and
- The southern sea otter (Enhyrda lutris nereis), which lives in southern California.
Sea otters eat fish and marine invertebrates like crabs, urchins, sea stars, and abalone, as well as squid and octopuses. Some of these animals have hard shells, which protect them from predators. But that isn't an issue for the talented sea otter, which cracks open the shells by banging them with rocks.
To hunt prey, sea otters have been known to dive as deep as 320 feet however, males mostly forage at depths of around 260 feet and females about 180 feet.
Sea otters have a baggy patch of skin under their forelimbs which is used for storage. They can keep extra food in this spot, and also store a favorite rock for cracking the shell of their prey.
Halarachne sp. nasal mites infest harbor seals (Phoca vitulina) and southern sea otters (Enhydra lutris nereis) in California, but little is known about the pathophysiology of these infestations, or risk factors for exposure. To investigate these questions, a retrospective case-control study was performed using necropsy data from 70 mite-infested sea otters, and 144 non-infested controls. Case records for sea otters examined by pathologists from February 1999 through May 2015 were examined to assess risk factors for infestation, and lesions associated with nasopulmonary acariasis. Animals with a history of captive care within 10 days of death or carcass recovery were 3.2 times more likely to be infested with nasopulmonary mites than those with no history of recent rehabilitation. Sea otters stranding within 1 km of Elkhorn Slough in Monterey Bay were 4.9 times more likely to be infested with nasal mites than other areas this site is characterized by high sea otter contact with sympatric harbor seals (a common host for Halarachne sp.), and a comparatively large population of rehabilitated and released sea otters. Aged adult otters were 9.4 times more likely to be infested than younger animals, and sea otters with nasopulmonary acariasis were 14.2 times more likely to have upper respiratory inflammation than un-infested animals. Additional findings in otters with nasopulmonary acariasis included lower respiratory tract bacterial infections, presence of medium-sized and/or fresh nose wounds at necropsy (indicators of recent face-to-face interaction between otters during copulation or fighting), and turbinate bone erosion. Our findings, although preliminary, suggest that captive rehabilitation and close contact with harbor seals could facilitate nasopulmonary mite transmission to sea otters. We also identified a high-risk zone for nasopulmonary acariasis in sea otters. We also provide preliminary data to suggest that nasopulmonary mite infestations can cause significant respiratory pathology in sea otters.
Description and Range
The sea otter is the smallest of the marine mammals and the largest member of the weasel family (Mustelidae).
Ecology and life history
Sea otters are commonly found in rocky marine habitats and kelp beds within 1.2 miles of the coast. Females tend to use habitats closer to the shore than males.
In rough weather, otters take refuge among kelp or in coves and inlets.
It is a carnivore and feeds on urchins, crabs, clams, mussels, snails, and chitons. It uses rocks to break the shells and exoskeletons of its prey and expose the edible interior of these species. Predation by sea otters on urchins has been found to maintain stability within marine invertebrate communities the species is considered a keystone species because of this effect.
The dense fur of the sea otter made its pelt extremely valuable to fur traders, which led to overexploitation of the species in the 1700s and 1800s.
Otter mortality can result from oil spills and incidental capture in nets and traps set for fish, shellfish, and crabs.
The sea otter is found only in the northern Pacific Ocean. In Washington, it is limited in distribution to the marine waters from south of Destruction Island north to Cape Flattery, and east to Pillar Point in the Strait of Juan de Fuca. The Washington population had increased steadily from 59 individuals reintroduced in 1969 to 1970 to almost 1,600 otters in 2014.
For maps of distribution and conservation status of sea otter, check out NatureServe Explorer and the International Union for the Conservation of Nature Red List.
Sea otter numbers have declined in southwestern Alaska over the past 20 years. 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. In 2005, the U.S. Fish and Wildlife Service listed this distinct population segment as Threatened under the Endangered Species Act. See the Sea Otters and the Endangered Species Act page for more details.
- ^In the United States, white abalone (Haliotis sorenseni) were listed as endangered under the Endangered Species Act in 2001, and black abalone (Haliotis cracherodii) were listed as endangered in 2009. In Canada, northern abalone (Haliotis kamtschatkana) were listed under the Species at Risk Act in 2003.
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Keywords : sea otter, population, density, littoral, monitoring, translocation, fisheries, predation
Citation: Davis RW, Bodkin JL, Coletti HA, Monson DH, Larson SE, Carswell LP and Nichol LM (2019) Future Directions in Sea Otter Research and Management. Front. Mar. Sci. 5:510. doi: 10.3389/fmars.2018.00510
Received: 02 July 2018 Accepted: 21 December 2018
Published: 21 January 2019.
Rob Harcourt, Macquarie University, Australia
L. Max Tarjan, San Francisco Bay Bird Observatory, United States
Clive Reginald McMahon, Sydney Institute of Marine Science, Australia
Rebecca Ruth McIntosh, Phillip Island Nature Parks, Australia
Copyright © 2019 Davis, Bodkin, Coletti, Monson, Larson, Carswell and Nichol. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Sea Otter Conservation
California’s southern sea otter has been listed as a threatened species under the Endangered Species Act since 1977. 41 years later and counting, their conservation status remains unchanged and their future uncertain. Sea otter population growth has stalled in recent years and many hurdles for full population recovery remain. There are only about 3,000 southern sea otters left in the wild today.
Why Are Sea Otters Important?
Sea otters are an iconic species, representing the beauty and diversity of marine life found along California’s coastline. They’re also considered a keystone species because of their critical importance to the health and stability of the nearshore marine ecosystem. They eat sea urchins and other invertebrates that graze on giant kelp. Without sea otters, these grazing animals can destroy kelp forests and consequently the wide diversity of animals that depend upon kelp habitat for survival. Additionally, kelp forests protect coastlines from storm surge and absorb vast amounts of harmful carbon dioxide from the atmosphere. Sea otters are also considered a sentinel species because their health reflects that of California’s coastal waters.
Why Aren’t They Recovering?
Recent studies have shown that fatal white shark bites have increasingly become the leading cause of sea otter mortality in California, a concerning trend that is likely impacting range expansion and population recovery. Scientists also attribute a substantial percentage of southern sea otter mortality to infectious diseases, many of which are known to have anthropogenic causes and land-to-sea linkages. White shark bites, pathogens and parasites, food availability, nutritional deficiencies, habitat degradation, coastal pollutants and contaminant exposure are among many of the contributing factors threatening the recovery of the species. And the risk of a major oil spill remains a serious threat.
What’s Being Done About It?
Researchers are working hard to gain a better understanding of what’s threatening sea otters so we can find ways to help them recover. Determining precisely how all of the factors driving elevated mortality are impacting the overall health of the southern sea otter population and the nearshore marine ecosystem on which they and other species depend is critical. The goal is development and implementation of effective, long-term management and mitigation strategies that can lead to the recovery and delisting of the species.
Threats and Issues
The single greatest cause of southern sea otter mortality by far is fatal white shark bites. Shark-bitten sea otters now account for more than half of all stranded sea otters recovered in California, exceeding all other causes of sea otter mortality combined. The increase in shark bite mortality now appears to be impacting population growth and expansion at the peripheries of the range, areas of the population that typically fuel the colonization of new habitats. Sea otter range expansion to the north and south will be critical for full recovery of the population but unfortunately these are the very areas where increased shark bite mortality has been greatest.
Disease and Contaminants
California’s sea otters acquire many infectious diseases because of elevated pathogen and contaminant pollution levels in nearshore waters. Part of sea otters’ high susceptibility to exposure is due to their diet. With incredibly high energy requirements, sea otters must consume approximately 25% of their bodyweight in prey each day just to stay alive. A large proportion of this prey consists of filter-feeders, such as mussels and clams. These organisms indiscriminately sieve particles out of the water and can accumulate high concentrations of pollutants and disease pathogens. When otters repeatedly forage on these contaminated prey, over time they can expose themselves to harmful or even lethal doses.
Sea otter harassment and other wildlife disturbance represents more than 40 percent of all violations recorded annually in Monterey Bay National Marine Sanctuary. The harmful consequences harassment can potentially have on sea otter adult females, especially those caring for pups, is particularly concerning. The demanding maternal costs associated with pup rearing for adult female sea otters make them exceptionally vulnerable to energetic deficits — this includes the additional energy expenditure caused by harassment by humans. I f a resting otter is harassed and forced to dive, the animal must expend additional energy to swim away only to begin grooming all over again, which takes away precious time it would otherwise have to rest or care for its young undisturbed. Research has revealed that females with 6 month old pups spend up to 14 hours a day foraging, while consuming nearly twice as much food as females with no pups. Their daily energetic demands are challenging enough, but superimpose harassment on top of an already strenuous energy budget and it may be ultimately too much for the animals to overcome, making them more vulnerable to infection and disease, and increase the likelihood they abandon their pups as they aren’t able to provide for them.
California Sea Otter Fund: $3 Million and Counting
Since it’s inception in 2007, the California Sea Otter Fund has provided critical support for sea otter research and conservation. The Fund has raised over $3 million through the generous and continued support of otter-loving Californians. Each year the Fund must meet a target goal in order to stay on the tax form the following year so please consider making a tax-deductible donation to the California Sea Otter Fund when you file your state income taxes, even if it’s a small amount. The money raised goes to the California Department of Fish and Wildlife and California Coastal Conservancy to fund research focusing on what’s threatening sea otter population recovery, public outreach and education, and ongoing investigations into sea otter harassment.
Californians, please remember sea otters when you file your taxes. Look for line 410 on Form 540. With only 3,000 southern sea otters left in the wild today, every otter counts!
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T1 - Sea otters (enhydra lutris) from the northern and southern populations may find each other in Humboldt County, California
N1 - Publisher Copyright: © 2019 IUCN Otter Specialist Group.
N2 - Sea otters (Enhydra lutris) are an apex carnivore and a keystone species, whose range contracted with population declines in last few centuries. But due to direct conservation efforts, both the northern sea otter (E. lutris kenyoni) and southern sea otter (E. lutris nereis) populations shown increases in the last few decades. The two populations are not connected, however, and southern sea otters in California are still threatened and endangered on the state level. The Humboldt County coast is situated between the southern sea otters in central California and the northern sea otters found between Oregon and Alaska. In 2015 a sea otter was seen in Humboldt Bay, the first sighting in Humboldt County since 2005. Although most sea otters found in Humboldt County are assumed to be from the southern sea otter population, genetic testing of a dead sea otter found in 2014 determined that it was from the northern sea otter population. The continued documentation of southern sea otters and the recent documentation of dead northern sea otter in Humboldt County suggests the Humboldt County coast may be an important area for linking the two populations in the future.
AB - Sea otters (Enhydra lutris) are an apex carnivore and a keystone species, whose range contracted with population declines in last few centuries. But due to direct conservation efforts, both the northern sea otter (E. lutris kenyoni) and southern sea otter (E. lutris nereis) populations shown increases in the last few decades. The two populations are not connected, however, and southern sea otters in California are still threatened and endangered on the state level. The Humboldt County coast is situated between the southern sea otters in central California and the northern sea otters found between Oregon and Alaska. In 2015 a sea otter was seen in Humboldt Bay, the first sighting in Humboldt County since 2005. Although most sea otters found in Humboldt County are assumed to be from the southern sea otter population, genetic testing of a dead sea otter found in 2014 determined that it was from the northern sea otter population. The continued documentation of southern sea otters and the recent documentation of dead northern sea otter in Humboldt County suggests the Humboldt County coast may be an important area for linking the two populations in the future.