The Status of Lavinia ardesiaca, a Cyprinid Fish from the Pajaro-Salinas River Basin, California

Abstract

HE Pajaro and Salinas rivers form the principal tributaries to Monterey Bay, along the coast of central California. The fish fauna of the Monterey basin has been treated in detail by Snyder (1913), who has shown that the strictly fluvial fishes are all derived from, and mostly identical with, those of the Sacramento River system to the north. During the routine identification of collections made by my father and me in the Pajaro and Salinas rivers in 1939, I noticed that my fin-ray counts for Lavinia ardesiaca Snyder (1913: 58-61, fig. 1), one of the endemic minnows, did not agree with those published by Dr. Snyder. His data showed that ardesiaca frequently had 9 dorsal and 9 anal rays, whereas my counts for these fins never fall below 10 (Tables V and VI). The range of variation given by Snyder (1913: table, page 59) in the dorsal and anal rays seems unusually extended for ardesiaca, as compared with exilicauda. In the two forms, the dorsal varied from 8 to 12 and 10 to 12, and the anal varied from 8 to 13 and 11 to 13, respectively. This led me to suspect that Snyder's material of ardesiaca did not comprise a genetic unit. In 1941, a preliminary analysis of critical material (kindly collected by R. G. Miller and W. I. Follett and donated to the University of Michigan) disclosed the probable source for Synder's low dorsal and anal ray counts. In those collections, hybrids between the Lavinia and another local minnow, Hesperoleucus symmetricus subditus2 Synder (1913: 67-70, fig. 3), were found. As demonstrated herein, the Hesperoleucus usually has 8 dorsal and 7 anal rays, in contrast to 10 or 11 dorsal and 11 or 12 anal rays in the Lavinia, whereas the number of rays in these fins in the presumed hybrids bridges the gap between those counts (Tables V and VI). The number of gill-rakers is also intermediate (Table VII). Circumstantial evidence for a hybrid interpretation of such intermediates is strong. This paper presents data showing: (1) that ardesiaca is preoccupied by Lavinia harengus Girard, described from Monterey; (2) that harengus cannot be specifically separated from Lavinia exilicauda Baird and Girard; and (3) that Lavinia and Hesperoleucus hybridize in the Monterey basin. The genus Lavinia (regarded herein as monotypic) is elsewhere known only from the Sacramento River system. The genus Hesperoleucus has a somewhat greater range for it is found from the Cuyama River basin (where introduced?), the next river system south of Monterey Bay, northward to the Navarro and Gualala rivers, throughout the Sacramento basin, and in the Warner Lakes drainage of south-eastern Oregon (Snyder, 1913: 63-70; Schultz and DeLacy, 1935: 379). The record for the Cuyama drainage is based on material at the University of Michigan. In both the original account of Lavinia harengus (Girard, 1856: 184),