The Channel Islands and surrounding waters support a great diversity of marine mammals, which can be divided into three groups: 1) whales, dolphins and porpoises (cetaceans); 2) seals and sea lions (pinnipeds); and 3) the southern sea otter.
Cetaceans live their entire lives at sea, while pinnipeds come ashore periodically to rest, breed, bear young, or molt. Pinnipeds depend on several haulouts and rookery sites throughout the Channel Islands. In California, sea otters normally spend their entire lives at sea, though some occasionally haul out on land. Marine mammals feed on fishes and invertebrates, which feed on other marine life in the Channel Islands region. The abundance and distribution of marine mammals is an important indication of the general health and ecological integrity of the sanctuary.
While all marine mammals are protected under the Marine Mammal Protection Act of 1972 (MMPA), some marine mammals are further protected under the federal and state Endangered Species Act. The Channel Islands provides an important habitat for at least 10 species of endangered marine mammals.
Whales, Dolphins And Porpoises
At least 33 species of cetaceans have been reported in the sanctuary region (Leatherwood et al. 1982; Leatherwood et al. 1987), of which seven are listed as endangered. Most of the reports involve live sightings although a few are known only from strandings. Common species found in the sanctuary include: Long-beaked common dolphin, Short-beaked common dolphin, Bottlenose dolphin, Pacific white-sided dolphin, Northern right whale dolphin, Risso’s dolphin, California gray whale, Blue whale, and Humpback whale. In winter and spring during the gray whale migrations, orcas are frequently reported in the region.
Seals and Sea Lions
The productive waters and relatively undisturbed environment of the sanctuary provides vital habitat for pinnipeds, offering important feeding areas, breeding sites, and haul-outs. Three species commonly found throughout or in parts of the sanctuary are the California sea lion, northern elephant seal, and Pacific harbor seal. Rare or uncommon species sighted within the sanctuary include the northern fur seal, the Steller sea lion and the endangered Guadalupe fur seal.
Sea otters were common in the Channel Islands until prolonged periods of hunting led to local extinction at the Islands and severe depletion along the mainland California coast. After an international treaty in 1911 banned sea otter hunting, the population has increased slowly, however with drastic fluctuations due to fishing gear entanglements, disease, shark attacks, shooting, and starvation. In 2007 the USGS Western Ecological Research Center sea otter spring survey found 106 independent sea otters and zero confirmed pups south of Point Conception.
Although long-term status of the sea otter population is unclear, the geographic range of the population has expanded to the north and south. The recovering California population of sea otters now ranges from Point Conception north to Año Nuevo Island in Santa Cruz County. As a result of threats to sea otters due to their small population and limited range, a translocation project to reintroduce otters to part of their historic range was started in 1988, yet met with limited success. Between 1988 and 1990, 140 otters were translocated to San Nicholas Island and while some stayed, many swam away, died, or disappeared and were unaccounted for. As of 2010 only 46 otters were found at the San Nicholas. Sea otters are now occasionally spotted in the sanctuary, however the possibility remains that they could reestablish their range within sanctuary boundaries (USFWS 2005). The southern sea otter is listed as threatened under the federal Endangered Species Act and fully protected under California state law.
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