ch10-taxonomic

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Taxonomic Considerations

Another factor to consider in release strategies is the overall risk to the population of sea otters from an oil spill. Currently, the population of sea otters in Alaska is considered a subspecies (Enhydra lutris kenyoni); one that originally extended southward through British Columbia, Washington, and Oregon (Wilson et at, 1991). Although the EVOS may have killed several thousand sea otters (Doroff et al., 1993; Garrott et al., 1993), it did not place the northern subspecies of sea otter, which numbers more than 100,000 animals (Calkins and Schneider 1985, USFWS unpublished data), at biological risk. Given the low risk to the Alaskan population and the northern subspecies as a whole, more costly and controversial release strategies to safeguard the releasable sea otters, such as long-term holding, were not necessary.

If possible, rehabilitated sea otters in Alaska should be released within the subpopulation of their origin, which increases the probability that an individual will be familiar with that area and the food types available in that area. Table 10.1 lists suggested subpopulations of sea otters in Alaska that were identified by the State of Alaska as potential management units when they requested return of management of marine mammals during the late 1970s. These areas were defined in part by the locations of remnant populations, transplant locations, and geographic considerations such as habitat discontinuities.

Sea otter populations in California, Washington, and British Columbia are discontinuous. The population in California also is afforded sub specific status (E. l. nereis) based on skull morphology (Wilson et al., 1991). Although the genetic uniqueness of the California population is unclear, preservation of that gene pool is the safest course of action, perhaps justifying more extreme measures for safeguarding rehabilitated animals if an oil spill were to occur there. Whereas rescue efforts following the EVOS had little effect on the overall population in Alaska, similar efforts expended on behalf of the southern sea otter in California could be significant, especially if a large oil spill affected their entire 300-mile range.

The range of E. l. nereis presumably extended from Morro Hermoso in Baja California, Mexico (Kenyon, 1969) north to the California-Oregon border (Wilson et al., 1991), leaving a large area of unoccupied habitat suitable for relocation if necessary. However, any attempts to relocate sea otters to northern California will be met with considerable resistance from some segments of the public because of important commercial and recreational shellfish fisheries. An oil spill in the range of the southern sea otter could create a real dilemma for releasing rehabilitated sea otters, perhaps necessitating long-term holding until the habitat is sufficiently recovered.

Sea otter populations in both Washington State and British Columbia resulted from transplants of individuals from Alaska (Jameson et al., 1982); taxonomically they belong to the northern sea otter, E. 1. kenyoni. Presumably sea otters in those locations are genetically similar to those in Alaska. If at all possible, rehabilitated sea otters from those areas should be released in coastal Washington State or British Columbia. However, the Alaska origin of those populations increases relocation options, should more extreme measures be needed. If populations in those areas were severely depleted by an oil spill, they presumably could be augmented with sea otters from Alaska. Furthermore, if Washington and British Columbia were severely affected by a large oil spill, perhaps rehabilitated sea otters from those populations could be released in Alaska.

ch10-Other Considerations

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Other Considerations

Disease

The risk of disease transmission from released sea otters to wild populations is an important and legitimate concern. Following the EVOS, some pathologists and the Alaska Department of Fish and Game were opposed to releasing rehabilitated otters because of concern about disease transmission to wild populations (Spraker, 1990). The risks to the wild population from disease potentially originated both from pathogens that existed in localized populations of sea otters prior to capture, and which could be spread more widely following relocation, and from novel pathogens to which the sea otters were exposed during captivity. It is Fish and Wildlife Service policy in Alaska that whenever release of rehabilitated animals to the wild is contemplated, state-of the-art measures for disease transmission prevention shall apply (USFWS, in preparation).

Duration of Captivity

The length of time sea otters are held in captivity should be minimized. Limiting holding times may reduce the risks of disease transmission and may reduce the risks of captive sea otters becoming dependent on humans for food.

Composition of Receiving Population

Because sea otters tend to segregate by sex, it may be advantageous to release rehabilitated animals in areas having otters of the same age and sex as those being released (Ralls et a1., 1992). This may reduce social stress and may enhance the probability of sea otters remaining in the release area.

Holding at Release Site

Ralls et a1. (1992) suggest that holding relocated sea otters at the release site enhances the probability they will remain in the release area. In their experimental relocation of California sea otters, these investigators held individuals for forty-eight hours. Although Rathbun et a1. (1990) did not come to a similar conclusion, it may be prudent to use prerelease holding facilities at the release site until better information on the efficacy of the technique is available.

ch10-Selection of Release Sites

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Selection of Release Sites

Sharpe (1990) described criteria that were used to evaluate release sites along the Kenai Peninsula for sea otters following the EVOS. These criteria included:

1) amount of habitat of shallow or moderate water depth,
2) amount of kelp,
3) amount of weather-protected habitat,
4) water quality,
5) distance from oiled areas,
6) suitability for post release monitoring,
7) number of sea otters already occupying the area, and
8) suitable transfer sites (helicopter landing zones).

These are reasonable criteria for evaluating specific release sites. Amount of kelp was used by Sharpe (1990) as an indicator of habitat productivity, but in many areas an abundance of kelp does not necessarily equate with abundant food resources for sea otters. Kelp may be uncommon in some coastal areas of Alaska, especially those dominated by soft bottoms in which bivalves make up the predominant foods of sea otters. Moreover, in some rocky areas, abundant kelp is a reliable indicator of heavy and persistent feeding by sea otters (VanBlaricom and Estes, 1988).

Obviously, the presence of other sea otters may be the best indicator that a particular habitat is suitable for sea otters. However, uncertainties associated with disruption of the social organization of otters already in the area may be an important consideration. In addition, placement of sea otters in an unfamiliar area may place them at a competitive disadvantage with local sea otters.

Through predation, sea otters are rapidly able to affect the quantity and size of sessile or slow-moving shellfish. Therefore, the only way to assure that food is not limiting to rehabilitated sea otters is to release them in unoccupied or recently occupied areas. However, as discussed above, this strategy will likely be met with considerable resistance by commercial, subsistence, and recreational fishermen who use the same resources as sea otters.

Prerelease intertidal and subtidal surveys in occupied habitats can reveal on a gross scale the relative abundance of prey in an area. However, because of the patchy nature of their food resources and the ability of healthy sea otters to thrive in areas of long-standing occupation where food appears limited, surveys undertaken to assess the abundance of food resources at potential release sites may be difficult to interpret.

Given the resolution of most habitat studies, it is unlikely that pre- and postrelease habitat surveys will be able to document any effects of the released animals on the abundance of sea otter prey.

Recent studies suggest that individual sea otters specialize in certain kinds of prey within a given habitat (M. Riedman, Monterey Bay Aquarium, personal communication; K. Lyons, University of California, personal communication). Therefore, it may be advisable to release sea otters in areas that contain populations of prey comparable to those from where they were captured.

The effect of releasing rehabilitated sea otters on the wild population is not known. Sea otters are gregarious animals with a complex social organization (Garshelis et al., 1984; Riedman and Estes, 1990). Although their social organization has been described in general terms, little is known about the importance of the social bonding that exists outside of mating and between mothers and pups. Capture, treatment, and temporary holding of sea otters undoubtedly are very disruptive to their social organization. Release of those sea otters may also cause stress depending on the release strategy. Relocating sea otters to an already inhabited area may disrupt both the rehabilitated animals and the receiving population.

ch10-Monitoring Released Sea Otters

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Monitoring Released Sea Otters

Several marking methods are available that will facilitate monitoring rehabilitated sea otters after release. Sea otters are routinely marked by securing colored flipper tags to the hind flippers Jameson, 1989; DeGange and Williams, 1990). Tag colors should be conspicuous and different from colors already in use on free-ranging sea otters in the release area. Because tag loss is known to occur, sea otters are also routinely marked with a small transponder chip for permanent identification (Thomas et a1., 1987; DeGange and Williams, 1990). Transponder chips are usually injected beneath the skin in the groin area.

Abdominally implanted radio transmitters (Garshelis and Siniff, 1983; Ralls et a1., 1989) provide the most dependable means of marking sea otters for studies requiring frequent observations of individuals. It may be important that some of the released sea otters carry such transmitters as part of a natural resource damage assessment to monitor their movements following release and to estimate survivorship and reproduction (Bayha and Kormendy, 1990). The radio-tagged animals should be released together with the majority of the rehabilitated sea otters, thereby assuring adequate sampling of the released population. Ideally, follow-up studies should be designed to evaluate stresses associated with implant surgery, capture, treatment, and long-term holding. Although it can be argued that the results of follow-up studies will not affect whether or not oiled sea otters are rehabilitated and released, an indication of postrelease survival and movements is important to guide future release efforts.

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Summary

Ultimately, the USFWS release strategy for sea otters following an oil spill will depend upon the geographic location of the spill, the geographic extent of oiled habitat, the severity of habitat damage, the biological risk to the affected sea otter stock, and the number of affected animals. Consequently, release strategies need to be tailored to each situation where sea otters are captured. To that end we offer the following general recommendations:

1) Rehabilitated sea otters should be used to fill any demand from aquaria before release to the wild is considered.
2) Holding time should be minimized for rehabilitated sea otters that are to be released.
3) In those situations where the extent and severity of habitat damage is limited, releasing sea otters in the general vicinity of the point of capture should give rehabilitated sea otters the best chance for survival. This strategy will also result in the least amount of risk to wild sea otters from disease transmission.
4) In those situations where the capture location and surrounding habitat are severely contaminated and may remain so for many years, sea otters should be relocated, preferably to areas already occupied by sea otters.
5) New techniques should be developed and tested to enhance the probability that relocated animals will remain in the release area.
6) Sea otters from different subspecies should not be mixed.
7) Because of potential management conflicts, rehabilitated otters should not be used to expand the existing range of sea otters, except perhaps in California, Washington State, or British Columbia, where no other alternatives may be available.
8) At a minimum, released sea otters should be individually marked with brightly colored hind flipper tags and a uniquely coded transponder chip.

It is presently difficult to recommend a specific distance to relocate sea otters. Relocated sea otters have traveled hundreds of kilometers to return to areas where they were captured (Monnet et al., 1990; Rathbun et al., 1990; Ralls et al., 1992; USFWS). Thus, it is conceivable that some relocated sea otters will find their way back to contaminated habitat. The advantages of relocating sea otters at distances great enough to discourage homing may be offset by the higher risks associated with relocating sea otters to unfamiliar places.

ch10-Literature Cited

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Literature Cited

Bayha, K., and J. Kormendy, eds. 1990. Sea otter symposium: Proceedings of a symposium to evaluate the response effort on behalf of sea otters after the T/V Exxon Valdez oil spill into Prince William Sound, Anchorage, Alaska, 17-19 April 1990. U.S. Fish and Wildlife Service Biological Report 90(12).

Calkins, D. G., and K. B. Schneider. 1985. “The sea otter (Enhydra lutris).” In Marine mammals species accounts. J. Burns, K. J. Frost and L. F. Lowry, eds. Alaska Department of Fish and Game, Game Technical Bulletin 7:37-45.

DeGange, A. R., and T. D. Williams. 1990. “Procedures and rationale for marking sea otters captured and treated during the T/V Exxon Valdez oil spill.” In Sea otter symposium: Proceedings of a symposium to evaluate the response effort on behalf of sea otters after the T/V Exxon Valdez oil spill into Prince William Sound, Anchorage, Alaska, 17-19 April 1990. K. Bayha and J. Kormendy, eds. U.S. Fish and Wildlife Service Biological Report 90 (12): 39499.

Doroff, A., A. R. DeGange, C. Lensink, B. E. Ballachey, J. L. Bodkin, and D Bruden. 1993. “Recovery of sea otter carcasses following the Exxon Valdez oil spill.” In Proceedings of the Exxon Valdez oil spill symposium. Anchorage, Alaska, Feb 2-5, 1993.

Garrott, R. A., L. L. Eberhardt, and D. M. Burn. 1993. Mortality of sea otters in Prince William Sound following the Exxon Valdez oil spill. Marine Mammal Science 9:343-59.

Garshelis, D. L., A M. Johnson, and J. A. Garshelis. 1984. Social organization of sea otters in Prince William Sound, Alaska. Canadian Journal of Zoology 62:2648-58.

Garshelis, D. L., and D. B. Siniff. 1983. Evaluation of radio-transmitter attachments for sea otters. Wildlife Society Bulletin 11:378-83.

Jameson, R. J. 1989. Movements, home range, and territories of male sea otters off central California. Marine Mammal Science 5:159-72.

Jameson, R. J., K. W. Kenyon, A. M. Johnson, and H. M. Wight. 1982. History and status of translocated sea otter populations in North America. Wildlife Society Bulletin 10:100-107.

Kenyon, K. W. 1969. The sea otter in the Eastern Pacific Ocean. North American Fauna 68:1-352.

Monnett, C., L. M. Rotterman, C. Stack, and D. Monson. 1990. “Postrelease monitoring of radio-instrumented sea otters in Prince William Sound.” In Sea otter symposium: Proceedings of a symposium to evaluate the response effort on behalf of sea otters after the T/V Exxon Valdez oil spill into Prince William Sound, Anchorage, Alaska, 17-19 April 1990. K. Bayha and J. Kormendy, eds. U.S. Fish and Wildlife Service Biological Report 90 (12): 400-409.

Ralls, K., D. B. Siniff, A Doroff, and A. Mercure. 1992. Movements of sea otters relocated along the California coast. Marine Mammal Science 8:17884.

Ralls, K., D. B. Siniff, T. D. Williams, and V. B. Kuechle. 1989. An intraperitoneal radio transmitter for sea otters. Marine Mammal Science 5:376-81.

Rappoport, A. G., M. E. Hogan, and K. Bayha. 1990. “Development of the release strategy for rehabilitated sea otters.” In Sea otter symposium: Proceedings of a symposium to evaluate the response effort on behalf of sea otters after the T/V Exxon Valdez oil spill into Prince William Sound, Anchorage, Alaska, 17-19 April 1990. K. Bayha and J. Kormendy, eds. U.S. Fish and Wildlife Service Biological Report 90 (12): 375-84.

Rathbun, G. B., R. J. Jameson, G. R. VanBlaricom, and R. L. Brownell, Jr. 1990. “Reintroduction of sea otters to San Nicolas Island, California: preliminary results for the first year.” In Endangered wildlife and habitats in Southern California. P. J. Bryant and J. Remington, eds. Memoirs of the Natural History Foundation of Orange County 3:99-114.

Riedman, M., and J. A. Estes. 1990. The sea otter (Enhydra lutris): Behavior, ecology, and natural history. U.S. Fish and Wildlife Service Biological Report 90(14).

Sharpe, E. 1990. “Sea otter release site selection and post-release activities along the Kenai Peninsula, Alaska.” Sea otter symposium: Proceedings of a symposium to evaluate the response effort on behalf of sea otters after the T/V Exxon Valdez oil spill into Prince William Sound, Anchorage, Alaska, 17-19 April 1990. K. Bayha and J. Kormendy, eds. U.S. Fish and Wildlife Service Biological Report 90 (12): 421-27.

Spraker, T. R. 1990. “Hazards of releasing rehabilitated animals with emphasis on sea otters and the T IV Exxon Valdez oil spill” In Sea otter symposium: Proceedings of a symposium to evaluate the response effort on behalf of sea otters after the T/V Exxon Valdez oil spill into Prince William Sound, Anchorage, Alaska, 17-19 April 1990. K. Bayha and J. Kormendy, eds. U.S. Fish and Wildlife Service Biological Report 90 (12): 385-89.

Thomas, J. A., L. H. Cornell, B. E. Joseph, T. D. Williams, and S. Dreischman. 1987. An implanted transponder chip used as a tag for sea otters (Enhydra lutris). Marine Mammal Science 3:271-74.

U.S. Fish and Wildlife Service. (In prep) “Sea Otter Response Plan.” In Alaska region oil and hazardous substances spill response contingency plan.

VanBlaricom, G. R., and J. A. Estes, eds. 1988. The community ecology of sea otters. New York Springer-Verlag.

Wilson, D. E., M. A. Bogan, R. L. Brownell, Jr., A. M. Burdin, and M. K. Maminov. 1991. Geographic variation in sea otters, Enhydra lutris. Journal of Mammalogy 72:22-36.

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Chapter 11 – Introduction

During an oil spill, large numbers of sea otters may arrive simultaneously at rehabilitation centers. Because facilities and veterinary personnel often are not equipped to handle more than five oiled animals at one time, it becomes necessary to develop a quick, straightforward system for evaluating animals and establishing priorities for treatment. This chapter presents criteria for evaluating large numbers of animals and for developing a triage program during a large scale emergency. Two types of large spills are considered, a short-term event such a tanker spill and a long-term event as occurs with an oil platform blowout.

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Triage for Oiled Wildlife

A triage program allows the rehabilitation team to classify and treat contaminated wildlife in a systematic manner. If all members of the team are familiar with the criteria or priorities, it provides the basis for providing the best care for the largest number of animals. Some animals may require immediate lifesaving procedures, while others may benefit from a period of stabilization. Critically ill animals with little chance of survival may create an unreasonable demand on veterinary resources. In these cases, euthanasia should be considered.

It is the responsibility of the rehabilitation team to assign treatment priorities for the different categories of contaminated wildlife. The triage system described here was developed for subadult and adult animals. Because sea otter pups require specialized care, they should be directed to nursery areas for immediate, full-time attention (see Chapter 9). The criteria used for ranking adult animals in different triage categories are based on: 1) toxicity of the oil encountered, 2) degree of external oiling, 3) stability of the animal, and 4) general medical condition.

Factors for determining these criteria are presented in Chapter 4 and Chapter 5. The condition of each otter arriving at rehabilitation centers depends on many unknown factors, such as the duration of oil exposure and the animals’ general health before the spill. However, triage criteria necessarily are limited to physiological and behavioral assessments of the animal once it arrives at the center.

For evaluating adult otters, we recommend the five-category triage rating system established for the treatment of war casualties (Bowen and Bellamy, 1988): 1) urgent, 2) immediate, 3) delayed, 4) minimal, or 5) expectant.

Urgent

Animals in this category require urgent intervention to prevent continued contamination or death. Their survival will depend on quick and efficient treatment. Heavily oiled otters contaminated early in the spill are placed in this category. The primary goal is to remove oil quickly and to avoid systemic contamination due to dermal absorption, inhalation, or ingestion during grooming. Fresh crude oil often irritates the otters’ sensitive membranes; excessive biting and scratching can lead to permanent damage of the cornea and interdigital webbing of the flippers. Animals displaying hypoglycemic shock and hypothermia fall within this category regardless of the spill phase. Treatments include washing (Chapter 6) and immediate medical attention (Chapter 5). Rewarming hypothermic animals, cooling hyperthermic ones, and administering fluids are indicated when appropriate. If presented with several animals in this category, animals displaying emergency medical conditions should be treated first.

Immediate

This group requires immediate washing and treatment of minor medical problems. Usually, survivorship is high if treatment is quick. Heavily oiled animals contaminated late in a spill and showing few medical abnormalities fall into this category. Also, moderately oiled animals captured during all phases of the spill, and animals showing moderate respiratory distress, mild hypoglycemia, or hypothermia require immediate attention. These animals are temporarily stable and tolerate short waiting periods as long as they are supervised. They should await treatment in thermal environments that allow them to maintain normal body temperatures and do not induce panting or shivering. Because of complications associated with anesthetic agents (Chapter 3), they should not be fed unless treatment is delayed for more than three hours.

Delayed

These animals can tolerate and will probably benefit from a period of rest before treatment. Moderately oiled otters contaminated late in the spill and showing no clinical or behavioral signs of distress should be placed in the delayed category. Other animals in this category include lightly oiled or unoiled otters with minor clinical signs (periodic agitation or shivering, etc.). These animals often will accept food; food, water, and rest are recommended while they await treatment. The period of stabilization can range from twelve to twenty-four hours with little adverse effect. These animals are treated after Urgent and Immediate Care animals are handled.

Minimal

Animals in this category require minimal or no cleaning and often only require a general physical examination. A stabilization period of twenty-four to thirty-six hours is recommended. Food and water should be offered to alert animals every three hours throughout this period. The animals must be supervised during stabilization. Tests may be necessary to determine if the fur is oiled; treatment and washing will be based on the results of these tests. If the results for oiling are negative and the veterinary staff has determined that the animal is healthy, then we recommend moving these animals quickly to long-term holding areas. Lightly oiled and unoiled otters showing no clinical signs of distress comprise this category.

Expectant

This category includes all animals that behaviorally and clinically have little expected chance of survival. They should be made comfortable during a brief period of observation. The primary criteria for placement in this category is severe subcutaneous emphysema as determined by palpation. Usually the condition is irreversible and is associated with other severe medical conditions. During the Exxon Valdez oil spill (EVOS), otters with subcutaneous emphysema that displayed diaphragmatic and agonal breathing rarely survived twenty-four hours in the rehabilitation center. A veterinarian should be consulted to determine if euthanasia is the most humane alternative for animals in this category.

ch11-Short-Term versus Long-Term Spills

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Short-Term versus Long-Term Spills

The assignment of animals to one of the five triage categories will change with the phase and type of spill. In a catastrophic spill, oil is released in a single event and degrades relatively uniformly with time. As a result, the degree of contamination and the associated medical problems of wildlife decline with time and subsequent weathering of the oil. This was observed for sea otters following the EVOS (Table 11.1). The highest percentage of urgent care animals arrived during the first three weeks of the spill. Later in the spill, a greater proportion of animals required only minimal care.

Chronic spills, such as oil platform blowouts and incidents like the Persian Gulf spill, involve the long-term release of fresh oil into the environment. A consequence of chronic spills is prolonged contamination of wildlife by oil containing the highest concentrations of aromatic compounds. Because these compounds are considered the most toxic components of oil, a chronic spill may lead to a prolonged, high incidence of medical problems. Triage will be more difficult during a chronic spill because most animals will require urgent or immediate care until the release of oil is stopped.

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Summary

A triage program provides a systematic approach for sorting large numbers of contaminated wildlife for medical care. This program depends on the phase and type of oil spill. During spills of short duration, Early (less than three weeks post spill) and Late (more than three weeks post spill) Phases are easily distinguished. In contrast, the distinction between phases of a chronic spill will be more nebulous and will depend on several factors including the duration of oil release. For either type of spill, the greatest number of urgent care animals arrive during the Early Phase. The Late Phase is characterized by increased numbers of animals requiring minimal care.