Oiled Sea Otter Capture Course


Following an oil spill, the decision to initiate a capture effort for sea otters must not be made lightly. The authorities legally responsible for conserving and protecting sea otters must be contacted. They will determine the best response option. For all oil spills, it is important to emphasize that the primary response option should be to prevent contamination of animals. Spill diversion and skimming techniques should be used to keep oil away from sensitive sea otter habitat – especially kelp beds, rafting areas, and intertidal mussel beds. Response options such as hazing, herding and other deterrent measures, have been unsuccessful for protecting sea otters (Davis et a1., 1988a), but additional research is warranted. If prevention measures fail, it may be necessary to implement a sea otter capture operation.

Factors that should be considered include: 1) influence of environmental, meteorological, and oceanographic conditions, 2) specific characteristics of the spill, such as the type, amount and distribution of oil, and 3) vulnerability of the sea otter population to the spill (Baker et a1., 1981; Siniff et a1., 1982). Local weather and marine conditions will also affect capture efforts and must be factored into any proposed field operation. Areas where effective capture efforts have taken place include embayments, protected waters, and kelp beds during calm weather. Weather and sea conditions must be safe for capture teams and the associated support operations. If safety can not be ensured, then the emphasis for protecting sea otters must be placed on prespill and preventative spill measures.

Once the above factors have been considered and the decision is made to capture sea otters, program effectiveness will depend on the spill size, timeliness of captures, and availability of rehabilitation facilities. During small spills, the most appropriate response may be limited to notifying trained personnel and basic preparation of equipment in case otters become oiled. A capture program may be unnecessary due to adverse environmental factors or movement of oil out of the sea otter area. Large spills may involve enormous numbers of personnel and, undoubtedly, most of the available response resources. In order to initiate the most effective capture effort, the risk of the spill to sea otters must be assessed and reassessed with respect to its size and direction of movement. All decisions to conduct a capture operation must balance the potential threat of the oil to otters and the risks associated with capturing and handling wild animals (Stulken and Kirkpatrick, 1955).

If the probability of sea otter contamination is remote, initial efforts should consist of daily surveys to determine the distribution of sea otters relative to the movement of oil. Selected areas should be surveyed daily for oiled sea otters and evidence of environmental contamination. Throughout the response period, these areas should be monitored for notable changes. Until the threat of oiling is past, any changes in sea otter behavior and significant population shifts with respect to the location of oil should be recorded. Only experienced biologists with knowledge about the natural behavior of sea otters should conduct these surveys.

When otters are in danger of oiling, preemptive captures may be considered. The term preemptive capture refers to the capture of healthy, uncontaminated sea otters preceding the spread of oil into their range. Uncontaminated otters are captured for their protection and placed in holding pens at predetermined sites or relocated to a safe habitat as determined by federal and state authorities. The techniques for conducting a preemptive capture include Wilson traps, dip nets, and entangling nets. Entangling nets are especially useful because they are capable of quickly capturing large numbers of healthy sea otters. Preemptive captures may be limited by weather conditions, inaccessible habitats, or during a catastrophic spill.

It is important to initiate capture operations quickly once oil moves into the sea otter’s habitat and animals become contaminated. Oiled sea otters captured in contaminated areas are designated contaminated captures. Attempts should be made to capture as many oiled animals as possible in order to: 1) remove contaminated animals and carcasses from the environment, 2) obtain immediate medical care for oiled otters, and 3) survey areas that appear to be threatened or heavily affected. Dip nets and entangling nets will generally be used for contaminated captures. Because contaminated areas are not safe for divers, diving operations should be suspended or limited to clean capture areas. Dip net techniques will be most effective in the early phase of a spill when the oil is most toxic. During this period contaminated animals will often be sick, lethargic and may exhibit a variety of unusual behaviors (Davis et al., 1988b). Aberrant behaviors include aggressive grooming by pawing and chewing at the skin, shaking the head violently, and floating low in the water. Otters may also haul out on land, presumably in an effort to reduce heat loss associated with decreased insulation in water (Costa and Kooyman, 1982; Williams et al., 1988). Heavily oiled sea otters will have pelage with a spiked or pointy appearance; they may be less attentive and more sluggish than healthy otters, and therefore, easily captured with dip nets. Moderately to lightly contaminated animals may not demonstrate significant differences in behavior or appearance.

The acute medical problems associated with oil contamination diminish as the more volatile toxic components of the spilled oil evaporate (see Chapter 4). This results in a decreased percentage of moribund animals. As sea otters become more active and more difficult to capture with dip nets, the effort should shift to entangling nets. The size of the spill and the number and distribution of otters still at risk will determine the number of capture teams needed.

Sea otters that do not appear to be oiled or show only a minor amount of oiling are occasionally taken during a capture operation. These captures are termed clean captures to differentiate them from preemptive captures and contaminated captures. This nomenclature facilitates record keeping and allows all animals to be categorized for the natural resource damage assessment process. Veterinarians in the field and at the rehabilitation facility will determine the health status of these animals. Examination results should be reported daily to the field personnel. This information will help capture teams decide the most appropriate capture areas and when to terminate capture operations.

Some animals will not need to be cleaned and may be moved directly to long-term holding facilities or released into suitable habitats. If the local environment is not safe and regulatory authorities permit, the otters may be translocated. If a significant amount of oil remains in or threatens an area, then clean otters may be captured and held until the threat is past. For example, beached oil may become resuspended in the coastal currents with each tidal cycle and poses a continuous threat. Oil that passes by one area can be redirected quickly by changing winds and currents. Thus, local clean areas cannot be considered safe havens. They must be constantly monitored so that capture operations can be initiated if a threatening situation arises. Such situations can occur days or even weeks after the immediate threat appears to have passed. Daily surveys conducted by federal and state resource agency personnel should be adequate for assessing the threat.

When oiled sea otter carcasses are recovered, the specimens must be documented and turned over to the appropriate agency’s law enforcement officers for evidence. The carcasses are retained for possible litigation and federal natural resource damage assessment. Carcasses should be designated as contaminated carcasses. Carcasses appearing unoiled should be retained for necropsy to determine the cause of death. All specimens should be documented and necropsied before they are turned over to law enforcement officers for evidence. Uncontaminated carcasses should be designated as clean carcasses and disposed of under the appropriate federal and state guidelines for marine mammals.