Biologists with the Division are currently attempting to determine preferred habitats of pelagic sharks along the U.S. West Coast, by analyzing fishery observer records, skipper bridge logs, and recreational fishing boat log data. The purpose is to determine the areas within the U.S. territorial waters (Exclusive Economic Zone or EEZ) that are occupied by our migratory pelagic sharks and necessary for feeding, spawning, breeding or growth to maturity. This work, still in the preliminary stages, is in support of the Pacific Fishery Management Council’s efforts in developing a Fishery Management Plan for highly migratory fish species
Blue Shark Habitat
Pups and juveniles occur in epipelagic, oceanic waters throughout the U.S. West Coast EEZ from the Mexico border north to the Canada border generally beyond the continental shelf (seaward of the 100 fm isobath).
Mako Shark Habitat
Oceanic and epipelagic from the U.S.-Mexico border northward to Washington; most common off California. Occurs from the surface to at least 150 m depth, with catches associated with sea surface temperatures ranging from 15EC to 25EC. Habitat off the coast is mostly occupied by juvenile fish and some small adult males; adult females and large males seldom occur in the EZZ except occasionally around the California Channel Islands and outer banks of the Southern California Bight in late summer. Nursery habitat utilization appears concentrated in the Bight south of Los Angeles.
White Shark Habitat
Along the U.S. West Coast it distributed sparsely along the coast with small groups of individuals observed near major pinniped rookeries, especially around colonies of the northern elephant seal. Most white shark interactions with seals and sea lions at the Farallon Islands rookery off central California occur in shallow water from 4-12 m (2-6.6 fm) deep. The majority of white shark capture records off the U.S. West Coast have been over bottom depths less than 80 m (44 fm) with the median depth 20.6 m (11.3 fm), though some were taken in water as shallow as 5.5 m (3 fm) and as deep as 366 m (200 fm). Documented white shark attacks on humans (1926-1983) are primarily close to shore, occurring from San Miguel Island, southern California, north to off Cannon Beach, Oregon. The Southern California Bight appears to be a nursery area for this species, while larger juveniles and adults occur more frequently north of Point Conception.
Until recently, white sharks off the US West Coast were thought to be restricted only to relatively shallow waters over the continental shelf as described. But recent satellite archival tagging by Boustany et al (Nature, Vol. 415, 3 Jan 2002) has revealed another oceanic pelagic and deeper water existence as well. Four white sharks tracked for 4-6 months experienced a near-shore phase, then moved offshore where they remained exclusively pelagic, one traveling 3,800 km to waters off Hawaii, and others southwestward to a region of the subtropical eastern Pacific off Mexico.
Common Thresher Shark Habitat
Prefers areas associated with high biological productivity and an abundance of the small schooling fishes upon which it feeds within the epipelagic zone above 200 m, often near or at the surface. The young pups occur off beaches, in shallow bays in nearshore waters from the U.S. Mexico border north to off Santa Cruz, CA, primarily in water less than 100 fathoms deep. Larger juveniles in open coast bays and offshore, ranging further north to off Pigeon Point, CA, and sometimes to San Francisco Bay during warm water years. Adult common threshers also occur off beaches and open coast bays, but tend to occur in deeper water and further north seasonally to Cape Flattery Washington. Preferred sea surface temperatures 56E-72EF ( 13EC to 22EC).
Pelagic Thresher Shark Habitat
The more tropical pelagic thresher shark generally moves into California waters during periodic warm water episodes relating to El Nino conditions, being more abundant to the south off the Pacific coast of northern Mexico. When it occupies epipelagic habitat within the U.S. West Coast EEZ, it usually does not range north of southern California waters. Associated with sea surface temperatures 21EC and warmer.
Bigeye Thresher Habitat
An epipelagic and mesopelagic species occurring off the U.S. West Coast from the Mexico border north to off cascade Head, Oregon. Ranges deeper than the other thresher species; to 723 m deep and can reportedly stay in cooler water for longer periods of time than other pelagic sharks. Population off California are predominantly adult males (71% of the observed catch). There is no evidence of nursery habitat within the U.S. West Coast EEZ.