Marine Mammals in California
California's coastal waters harbor species from three of the four orders of marine mammals. The Order Pinnipedia includes sea lions and seals; Cetacea includes whales, dolphins and porpoises; and Carnivora includes sea otters.
The California sea lion is the most abundant pinniped species found in California. Its breeding range extends from San Miguel Island in the Southern California Bight south to Isla Margarita on the Pacific coast of Baja. During nonbreeding season, male California sea lions migrate as far north as British Columbia. The returning southward migration begins in early spring. California sea lion numbers have increased dramatically on mainland haul-out sites, for example the harbor breakwall at Monterey and Pier 39 in San Francisco, where the mammals represent both a tourist attraction and a nuisance.
Opportunistic feeders, California sea lions prey on a variety of fish: sea lions have learned to take fish directly off fishermen's hooks, wreaking economic loss on recreational fishermen and commercial salmon fishermen. At the Ballard Locks in Seattle, California sea lion predation has contributed to the threatened extinction of a run of steelhead.
Population trend: In 1986, scientists estimated the total west coast population at approximately 177,000, with about 87,000 sea lions in California. Per capita growth rate is estimated at 6.4 percent annually. At that rate, the California sea lion population in 1992 may have exceeded 126,000 animals in California. Annual pup production in 1990 exceeded 25,000. In ocean cycles like the recent El Nino, elevated population levels resulting from total protection intensify competition for limited food resources, causing starvation and stranding of pups, eventually leading to population die-offs.
The northern elephant seal's recovery from near extinction is a well- documented success story. From a remnant population at the turn of the century, the species has reoccupied traditional rookeries and hauling grounds, and may have expanded its range beyond historic limits. Mainland rookery sites now occupied may not have been available 100 years ago due to predation by wolves and grizzly bears, which are no longer present.
Nonbreeding elephant seals range as far north as the Gulf of Alaska and are seasonal visitors in Oregon and Washington. Original rookery grounds extended from Cabo San Lazaro, Baja California, northward to Point Reyes, in northern California. The species now breeds at several islands in Mexico, as well as throughout the Channel Islands, Ano Nuevo Island and Point, the South Farallon Islands, and Pt. Reyes.
Population trend: Growth rate is estimated at 8.75 percent per year. A 1988 population estimate found a minimum of 60,000 elephant seals in U.S. waters.
Another California success story is the recovery of the gray whale.
The eastern stock of gray whales, sometimes called California gray whales, migrates annually between summer feeding grounds in the Bering and Chukchi Seas and winter breeding grounds along the west coast of Baja California. The southern migration begins in early October, arriving in California by late November. The northward migration in California waters generally begins in mid-February for whales without calves, and March continuing through May for cows with calves.
A baleen whale growing to 46 feet in length, most gray whales calve in Mexican waters. The young are born underwater and are able to swim on their own immediately, although they depend on a milk diet for at least 6 months. Gray whales grub along the bottom for tiny crustaceans, the staple of their diet.
Population trend: The most recent population estimate, which is based on the 1987-88 migration census, is 21,113 gray whales. Thought to have surpassed historic population levels, gray whales were removed from the Endangered Species List in 1992.
The harbor seal is found from the Bering Sea in Alaska along the west coast to southern California. The species is abundant throughout the coastal and estuarine areas of Washington and Oregon. In California, harbor seals are abundant along the entire coast. Their smaller size, chunky shape, lack of external ears, and spotted coat distinguish harbor seals from sea lions.
Harbor seals feed opportunistically on fish, squid, and octopus. In Oregon, harbor seals congregate in bays and estuaries to gorge on salmon and steelhead runs. In California at certain times of year, harbor seals prey heavily on fish caught in nets. Early in the year, gillnetters for California halibut in many areas may lose up to 80% of their catch to harbor seals.
Population trend: Surveys in 1987 placed the California harbor seal population at about 20,000 animals. Harbor seal abundance is increasing at 6% per year.
Common dolphins are a pelagic species distributed worldwide in temperate to tropical waters (12 - 28C). In the northeastern Pacific, the primary range of the common dolphin is the California-Oregon border to Costa Rica. Two stocks of common dolphins identified in California waters are the northern temperate, found offshore from about Isla Cedros north, and the Baja neritic, found close to the coast from San Diego south.
Population trend: The common dolphin is the most abundant cetacean in California, often observed riding the bow wave of boats and "porpoising" out of the water. The Eastern Tropical Pacific may harbor over 5 million common dolphins, one of several species inhabiting that area. In California the largest herds are seen from summer to autumn -- more than 57,000 dolphins estimated in 1983. According to research by the Inter-American Tropical Tuna Commission, the population is stable.
In the Pacific, harbor porpoise range from Alaska to central California. Their Atlantic relatives, a familiar species around the British Isles, were the first to be given the name "porpoise", derived from the Latin Porcus piscis, or "pig fish." In Great Britain porpoise are also called "herring hogs" for their practice of robbing herring nets.
Reaching 6 feet in length, harbor porpoise, as their name suggests, frequent bays, harbors, and other inshore waters, occasionally traveling up rivers. These porpoise usually feed on bottom-dwelling fishes, sometimes on squid, and occasionally on clams or crustaceans.
Population trend: Surveys conducted in the mid-1980's estimated harbor porpoise abundance from Washington to central California to be about 50,000 animals, with nearly 12,000 in northern and central California.
Department of Fish and Game (CDFG) observations of the halibut set net fishery in the San Francisco Bay area during the 1980's recorded unintentional taking of harbor porpoise. The fishing industry cooperated with CDFG and the Legislature to enact gillnet closures inside 40 to 60 fathoms from Point Reyes to the northern edge of Monterey Bay, and within three miles around the Farallon Islands. The closures curtailed the halibut gillnet fishery in the area; however, harbor porpoise mortality in the nets also declined sharply. Per capita growth rate for harbor porpoise is estimated at about 7 percent per year. The west coast population may be near its optimum level.
The historic range of sea otters extended from northern Japan across the Aleutian archipelago to Alaska and down the west coast to Baja California. By the early 1900's, intensive fur hunting had eliminated the species from most of its range, leaving remnant populations in a few Alaskan outposts and one small colony in California. In a remarkable comeback, sea otters have recolonized most of their Alaskan range. "Northern" sea otters are considered to be at their optimum sustainable population (OSP). In California the primary sea otter range extends from Point Ano Nuevo, south of San Francisco, to Santa Barbara County, stretching over 200 miles along the central coast.
The California sea otter recovery has sparked a controversy unparalleled in the annals of wildlife management. Scientists disagree on whether California sea otters are genetically distinct or the same as their Alaskan counterparts. An isolated population in any case, California's "southern" sea otters were listed as "threatened" under the Endangered Species Act in 1977 (the U.S. Fish and Wildlife Service classified them as a separate subspecies). Protective laws mandate the recovery of the California otters to OSP. However, fishermen protest that sea otters decimate valuable shellfish resources.
Indeed, the one point of agreement is the sea otter's voracious appetite. Lacking blubber, sea otters must consume 25 percent or more of their body weight daily to survive the ocean's chill. That's 10 to 15 pounds of shellfish a day for an average otter: the menu includes sea urchins, abalone, crab, clams, and spiny lobster. In a compromise designed to recover otters and conserve valuable shellfisheries, Congress passed a special law to translocate a colony of otters to San Nicolas Island in southern California, and at the same time, establish an "otter-free" management zone throughout the remainder of southern California, from which sea otters must be removed by all feasible non-lethal means.
Population trend: In 1938, the media heralded the "discovery" of a colony of about 50 sea otters at Bixby Creek, 15 miles south of Monterey. By the early 1940's, abalone divers were complaining about the loss of abalone in the sea otter range. By 1967 the herd was estimated at 600 animals, and a central coast abalone fishery that had sustained production averaging two million pounds a year since the early 1900's was on the wane. Commercial abalone diving on the central coast between Monterey and Morro Bay ceased in the early 1970's, as sea otters recolonized their central coast range.
In the early 1980's, sea otter population growth stalled. Sea otter mortality likely increased as the result of the 1982-83 El Nino: the warm-water cycle and winter storms uprooted kelp and caused abalone and urchin die-offs. Juvenile animals appeared emaciated; many likely starved. Moreover, CDFG observations on the gillnet halibut fishery operating on the central coast between Monterey and Morro Bay reported sea otters caught in the nets. The fishing industry worked with CDFG and the Legislature to enact a series of gillnet closures along the central coast. Nets are now prohibited inside 30 fathoms, and the closures have preempted the halibut fishery in the area. By 1988, sea otter numbers were again on the rise. The 1992 spring sea otter census counted 2,101 animals in the central coast range, including 291 pups. Growth rate is estimated at 5 to 7 percent per year. At that rate, scientists theorize that sea otters may recolonize the area between Point Conception and the Oregon border in approximately 22 years. Northern California waters harbor important fisheries for Dungeness crab and sea urchins, as well as a recreational diving fishery for abalone.