The Taxonomic Significance of the Kype in American Salmonids

Abstract

large heads and jaws which often are associated with the development of a pronounced hump in the back just posterior to the head. In the genus Oncorhynchus, the upper jaw elongates more than the lower jaw to form a snout. In Salmo and Salvelinus, the lower jaw elongates more than the upper jaw and often develops a hook at its tip which fits into a groove in the upper jaw to form a kype. Among American species of Salvelinus, or charrs, the kype reaches its maximum development in large males of the stream-spawning or anadromous forms, S. malma and S. fontinalis, whereas it is hardly discernible or is absent in large males of the lake-spawning or nonanadromous forms, S. alpinus and S. namaycush. Recent evidence of a kype developing in the anadromous or stream-spawning form of Arctic charr may indicate that the Salvelinus alpinus complex should be split into 2 species in America, a lake-spawning or nonanadromous Arctic lake charr, and a stream-spawning or anadromous Arctic brook charr.