. Cetaceans of the Channel Islands National Marine Sanctuary / prepared for National Oceanic and Atmospheric Administration, Channel Islands National Marine Sanctuary and NOAA, National Marine Fisheries Service by Stephen Leatherwood, Brent S. Stewart, Pieter A. Folkens. Whales California Channel FIGURE 56. White-sided dolphins frequently ride on the pressure wave of migrationg gray whales. ^ Photo off Anacapa Island, February 1985 by S. Leatherwood.) within several miles of Anacapa and Santa Cruz islands on both coasts, west and south of San Miguel Island, around Santa Barbara, San
. Cetaceans of the Channel Islands National Marine Sanctuary / prepared for National Oceanic and Atmospheric Administration, Channel Islands National Marine Sanctuary and NOAA, National Marine Fisheries Service by Stephen Leatherwood, Brent S. Stewart, Pieter A. Folkens. Whales California Channel FIGURE 56. White-sided dolphins frequently ride on the pressure wave of migrationg gray whales. ^ Photo off Anacapa Island, February 1985 by S. Leatherwood.) within several miles of Anacapa and Santa Cruz islands on both coasts, west and south of San Miguel Island, around Santa Barbara, San Nicolas and San Clemente islands, in the San Pedro Channel and near the Coronado Islands. During the past several years we have also found stranded white-sided dolphins at San Miguel Island. Within their broad range, Pacific white-sided dolphins appear to fluctuate in abundance seasonally. Earlier researchers speculated that such fluctuations were evidence of shifts in population centers off Northern California, in the SCB and off Baja California's west coast. We have been unable to unequivocally demonstrate migration in any area, although observed peaks in abundance suggest regular seasonal influxes into waters north of 40 N in spring and summer and between 25 N and 30 N in autumn. Apparently the only two areas in the Northeast Pacific in which observed distribution patterns are clearly not an artifact of sampling effort are the waters off Baja California and those in the SCB. Evidence for seasonal use is most convincing off Southern California, where peak numbers occur inshore from November through April and lesser numbers for the remainder of the year. It has been suggested that such movements are related to changes in prey distribution and water temperature. Northern anchovy, Pacific whiting (hake), and market squid appear to be the most frequently consumed prey of white-sided dolphins. These dolphins apparently do most of their feeding at night in the epipelagic and, to a
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