WHALE & DOLPHIN FACTS




(Information Provided By: Monterey Bay National Marine Sanctuary)

Thanks to its nutrient-rich waters, the Monterey Bay National Marine Sanctuary, located along California's central coast, offers some of the world's best whale watching. The central coast of California is one of only five regions in the world where major upwelling occurs. Cold, nutrient-rich water is driven to the surface as a result of wind, the angle of the coastline, and the rotation of the earth. The cold, deep water is filled with nutrients and during the spring when the northwest winds blow, this rich water is brought to the surface, fueled by the sun, and creates surface plankton blooms. Plankton form the base of the food chain for all marine animals. Whales, dolphins, and seabirds concentrate in the waters off central California to feed on an abundance of krill, fish, and squid supported by these intense plankton blooms. This extremely nutrient-rich area is centered around the Monterey Submarine Canyon which runs through the middle of Monterey Bay.

During the winter and spring months the entire gray whale population migrates through the Sanctuary within three kilometers of the Monterey Bay coastline, traveling to their summer feeding grounds in the Bering Sea and to their winter breeding grounds in Baja. Gray whales are rarely seen feeding in central California. Gray whales, especially calves, fall prey to killer whales and these events sometimes occur within the Sanctuary. Though virtually all populations of large whales are greatly reduced, the gray whale population is an exception. In 1988 the population was an estimated 21,100-23,000 individuals, probably close to its historical numbers.

During the summer and fall months, blue whales and humpback whales migrate to the Sanctuary to feed on their primary prey of anchovies and krill. An estimated 2,000-2,250 blue whales occur off California, moving along the entire coastline searching for their prey. Blue whales have been observed feeding on dense swarms of krill near Monterey and the Farallones. Humpback whales are one of the most common large baleen whales seen in the Sanctuary, but California estimates are significantly lower than those for blue whales. Humpback whales are seen most frequently off central California during the fall, feeding primarily on krill.

Gray Whale
Though virtually all populations of large whales are greatly reduced, the gray whale population is an exception: the population in 1988 was an estimated 21,100-23,000 individuals (U.S. Marine Mammal Commission 1995), probably close to historical values. Because almost the entire population of gray whales passes by Monterey within 3 km of the coast (Reilly et al. 1980), population estimates have been based on counts made periodically since 1967 (Buckland et al. 1993). Between 1967 and 1988, the average annual rate of population increase was 3.3%. Gray whales migrate annually from summer primary feeding areas off Alaska (Nerini 1984, Oliver and Slattery 1985) and secondary areas from Canada to California (Guerrero 1989, Hawkinson 1992, Oliver et al. 1984, Sumich 1984) to winter breeding and calving areas off Baja California, Mexico (Jones et al. 1984). Rarely are gray whales seen feeding in central California (Sund 1975, A. Baldridge pers. comm.). Most feeding on benthic amphipods and mysids occurs off Alaska (Kim and Oliver 1989,Oliver and Slattery 1985, Oliver et al. 1983). Gray whales, especially calves, fall prey to killer whales (Morejohn 1968, Baldridge 1972, Goley and Straley 1994).

Blue Whale
An estimated 2,000-2,250 blue whales occur off California (Barlow 1994, Calambokidis and Steiger 1995; Table 2). Blue whales may move along the entire California coastline during fall searching for euphausiid prey. Euphausiid swarms are often seen in great concentrations in Monterey Bay, due in part to physical mechanisms (e.g. upwelling, fronts, canyons, vertical walls) which may concentrate euphausiid prey (Harvey 1978, Schoenherr 1991). Blues have been observed feeding on dense swarms of euphausiids (dominated by either Thysanoessa spinifera or Euphausia pacifica) near Monterey (Schoenherr 1988, 1991) and the Farallones (Rice 1977, Kieckhefer 1995).

Humpback Whale
Humpback whales are one of the most common large baleen whales seen in the MBNMS, though California estimates are significantly lower than those for blue whales (Barlow et al. 1995; Table 2). Humpback whales were seen three times more frequently than other baleen whales on shipboard surveys conducted July 1994 to February 1995 off Point Sur (Harvey et al. 1995). Humpback whales are seen most frequently off central California during fall (Dohl et al. 1983); feeding, primarily on euphausiid prey, has been well documented around the Farallon Islands (Kieckhefer 1992). Most evidence indicates that the humpback whales feeding off California have moved north from areas used during winter off Mexico (Baker et al. 1986).

Minke Whale
Numerous sightings of minke whales have been documented in nearshore waters of southern Monterey Bay, Carmel Bay and south to Point Sur (Stern et al. 1990, A. Baldridge pers. comm.). As sightings are usually of single individuals, they are easily overlooked and therefore underestimated in aerial overflights (Dohl et al. 1983). Minkes are observed in the MBNMS year-round, though less commonly during winter (A. Baldridge pers. comm.).

Sperm Whale
The largest toothed whale, the sperm whale, is not frequently reported in the MBNMS (Barham 1982), although it is the most abundant large whale in the eastern North Pacific (Gosho et al. 1984; Table 2). Areas of deep water, where they often are associated, are infrequently surveyed (Fiscus and Niggol 1965). Dohl et al. (1983) considered sperm whales undersampled and relatively abundant. Note that Fiscus and Rice (1974) described food habits of 552 individuals taken from 1959-70, many of these in or close to MBNMS waters. Many of the sperm whales observed are greater than 30 km from shore and in the vicinity of the MBNMS (Fiscus and Niggol 1965, Carretta and Forney 1993). Recently, numerous sightings have been recorded near Pioneer Seamount during aerial surveys (J. Calambokidis pers. comm.). Sperm whales and beaked whales do at times occur relatively close to shore in the MBNMS because the of the deep water associated with the Monterey Canyon.

Beaked Whales
Beaked whales, like sperm whales, are closely associated with deep water, because they feed primarily on mesopelagic species of cephalopods and fishes. They are infrequently observed in California (Table 2). In 239 trips (from 1950 to 1955) to a station 11 km northeast off Point Pinos, Barham (1982) never observed beaked whales. However, Baird's beaked whales have been recorded annually during fall in MBNMS waters beyond Barham's cruise track (American Cetacean Society Monterey Bay 1980-1995). Because beaked whales are rare, usually found farther offshore, and are less approachable, these species are rarely seen or studied.

Killer Whale (Orca)
Killer whales are relatively uncommon, transient inhabitants of the MBNMS (Table 2). Killer whales off California likely move continuously along the coastline of western North America. Recently, three killer whales observed attacking gray whales in Monterey Bay, were identified as individuals previously seen in Glacier Bay, Alaska (Goley and Straley 1994). Transient killer whales often prey upon marine mammals, and gray whales and California sea lions are their primary targets in the MBNMS (Baldridge 1972, Morejohn 1968, Ternullo et al. 1993).

Pacific White-sided Dolphin
Pacific white-sided dolphins are the second most common cetacean observed off California (Table 2), with the greatest concentration off central California (Fiscus and Niggol 1965, Leatherwood and Walker 1982). This species was the most frequently seen dolphin in Monterey Bay by Barham (1982), though it has recently been replaced in abundance by common dolphins (pers. obs.). Pacific white-sided dolphins are commonly seen near the shelfbreak (primarily within 15 km west of Carmel Bay and within 25 km southwest of Santa Cruz) during fall and least abundant during spring (Black 1995).

Risso's Dolphin
Risso's dolphins are relatively common off California (Table 2). They were considered abundant in Monterey Bay in the late 19th century, but were seen infrequently in the bay from 1959 to 1975 (Leatherwood et al. 1980). Fiscus and Niggol (1965) reported 10 sightings of Risso's dolphins off central California from 1958 to 1961, six of which were within the MBNMS. There seems to have been a significant increase in the number of Risso's dolphins in the MBNMS since 1973 (Baldridge pers. comm.), and they can often be observed west of Point Pinos (Harvey et al. 1995, American Cetacean Society Monterey Bay 1980-1995).

Northern Right Whale Dolphin
Northern right whale dolphins are usually observed with other species. This species is most frequently seen south of the MBNMS (Fiscus and Niggol 1965). Like the Risso's dolphin, the Northern right whale dolphin appears to have increased in MBNMS waters since 1973; the two species are frequently associated (A. Baldridge pers. comm.)

Common Dolphin
Two morphological forms of the common dolphin have been described as two separate species; the long-beaked (Delphinus capensis) found closer to shore and the short-beaked (Delphinus delphis) a more pelagic species (Heyning and Perrin 1991). These dolphins are the most abundant cetaceans off California (Table 2), and are most concentrated in the southern California Bight (Forney et al. 1995). The abundance of long-beaked common dolphin has have increased recently in the MBNMS (A. Baldridge pers. comm.).

Dall's Porpoise
The Dall's porpoise is the most pelagic of the porpoises in the MBNMS, and was the most frequently seen cetacean in surveys off Point Pinos (Barham 1982). A large proportion of the Dall's porpoise sightings from 1958 to 1961 were within the MBNMS (Fiscus and Niggol 1965). This species is often seen over the Monterey Canyon (Harvey unpubl. data).

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