Hybrid Madtom Catfish, Noturus gyrinus x Noturus miurus, from Cayuga Lake, New York

Abstract

Three additional specimens of the hybrid combination Noturus gyrinus X N. miurus are described. Morphologically, they are similar to those previously reported by Trautman (1948) and Taylor (1969), being generally intermediate between the parental species. Hybrid vigor is indicated in one individual by its large size and robustness. All four specimens are females but only the largest appears to have been capable of reproduction. Ecological observations suggest that a combination of factors, including perhaps submarginal habitat and unequal numbers of the parental species, resulted in mismating to produce the hybrids. Madtoms may lack ethological barriers to hybridization which is characteristic of other ictalurids. INTRODUCTION Natural interspecific hybridization among the Ictaluridae appears to occur only rarely. Among catfishes, O'Donnell (1935) and Thompson (1935) reported possible hybrids between Ictalurus punctatus and Opladelus (=Pylodictus) olivaris from Illinois, but this identification is in doubt (Taylor, 1969). Trautman (1957) stated that the bullhead combination Ictalurus melas X I. nebulosus occurs commonly in Ohio, but he failed to include adequate descriptions. At least two cases of hybridization have been documented among madtoms. Taylor (1969) discussed a specimen from Oklahoma identified as Noturus exilis X N. miurus, mistakenly listed as Schilbeodes (=Noturus) miurus X S. nocturnus in Cross and Moore (1952). In 1930, Osburn et at., reported Schilbeodes nocturnus from western Lake Erie on the basis. of a single specimen, the first record of this fish from the Great Lakes drainage. After additional collections in the Great Lakes region failed to produce another example of that species, Trautman (1948) reexamined the original specimen and discovered it to be a hybrid, Schilbeodes mollis (z=Noturus gyrinius) X S. miurus. Taylor (1969) recently reported on four additional specimens of this combination from Indiana, Michigan and New York. Herein we describe three more gyrinus X miurus hybrids, all collected from Cayuga Lake, New York, and provide new information which may serve to explain the surprisingly high incidence of mismating among these two species. Aspects of the reproductive biology of madtoms are also discussed. MATERIALS AND METHODS All three hybrids were collected along the beach of Canoga Island, Cayuga Lake, Seneca Co., N. Y., by Brian J. Rothschild and associates. They are preserved in the Cornell University Fish Collection: CU