In Argentina, the Nototheniidae is represented by about 20 species, which mostly live in coastal waters of the continental shelf and slope. A few species inhabit inshore waters along the coasts of Patagonia and the Fueguian and Falkland (Malvinas) archipelagos and even reach rocky intertidal zones (Norman 1937, Hart 1946). Patagonotothen sima (Richardson 1844) is distributed in the Atlantic from the San Matías Gulf (around 42°S) to the Beagle Channel (54°50'S), inhabiting shallow waters including the intertidal zones. During faunal surveys in the rocky intertidal zone in Puerto Deseado, Santa Cruz (by A. Gosztonyi), it was noted that males of P. sima, one of the most common fish species in that habitat, appeared to have a higher second dorsal fin than the females.