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Eastern North Pacific species of the fathead sculpin genus Malacocottus Bean are assessed following examination of over 300 specimens collected from throughout the known range of the genus, from the west coast of North America around the Pacific Rim to Japan, including the marginal waters of the Salish Sea, Bering Sea, Sea of Okhotsk, and Sea of Japan. The results of this study demonstrate that two species of Malacocottus occur in the eastern North Pacific. Malacocottus zonurus is found in the North Pacific from Washington State around the Pacific Rim to Japan, and in all marginal seas. Malacocottus kincaidi Gilbert and Thompson is apparently endemic to the Salish Sea, known only from Puget Sound and the Strait of Georgia. These two species differ in preopercular spine morphology and gill-raker counts. Malacocottus aleuticus Smith, based on a single juvenile specimen, is a synonym of M. zonurus. This study includes redescriptions of M. zonurus and M. kincaidi, comparisons of both species with M. gibber, and a key to the three known species of the genus.
THE psychrolutid genus Malacocottus Bean contains seven nominal species, four of which have recently been considered valid: Malacocottus zonurus Bean, 1890; M. aleuticus (Smith, 1904); M. kincaidi Gilbert and Thompson, 1905; and M. gibber Sakamoto, 1930. Jackson and Nelson (1998) established the subfamily Malacocottinae for this genus, distinguishing it from their Psychrolutinae (Psychrolutes, Ebinania, and Neophrynichthys) by the presence of a rigid interorbital space and robust orbital ridge, and from other psychrolutids (Dasycottus, Eurymen, Ambophthalmos, and Cottunculus) by the absence of teeth on the vomer and reductions in the ossification of the cranial and infraorbital arches. Malacocottus is the only psychrolutid genus (sensu Jackson and Nelson, 1998) that has the combination of preopercular spines present and vomerine teeth absent.
Species of Malacocottus are generally deep-dwelling benthic fishes, though some have been collected in midwater trawls (Shinohara et al., 1992; Raring and Stevenson, 2010). The most widespread of these species, M. zonurus, is found from the west coast of North America around the Pacific Rim to Japan, as well as in the Bering Sea, Sea of Okhotsk, and Sea of Japan (Shinohara et al., 1992, 2009; Sheiko and Fedorov, 2000; Mecklenburg et al., 2002). In Japanese waters, the distribution of M. zonurus...