Aspects of the Ecology of the Hitch, Lavinia exilicauda (Cyprinidae), a Persistent Native Cyprinid in Clear Lake, California

Abstract

Growth, diet, and fecundity of Clear Lake hitch (Lavinia exilicauda chi) were investigated to see if any changes had taken place following the establishment of a large population of Mississippi silversides (Menidia audens) in the lake. No changes were found. Hitch seem to avoid competing with silversides for zooplankton by being limnetic in all except the early life history stages. Fecundity was found to be higher than that of Beardsley Reservoir hitch, but considerably lower than a previous estimate had indicated. The Clear Lake hitch (L. e. chi Hopkirk 1973) is one of only four (out of 12) native species that has managed to persist in large numbers in Clear Lake, Lake Co., California, following various environmental perturbations and the establishment of 16 exotic species (Moyle 1976). The hitch is a large (to 35 cm standard length), plankton-feeding cyprinid that spawns in the intermittent streams that enter the lake and is taken in small numbers by a commercial fishery. Although brief studies of its feeding habits were undertaken by Lindquist, Deonier, and Hanley (1943), and of its growth and reproduction by Murphy (1948), no studies have been undertaken since the establishment in the lake of the Mississippi silversides (Menidia audens) in 1967 (Cook and Moore 1967). The silversides is a small planktivore that now dominates the inshore areas. It has been introduced into reservoirs in Oklahoma and California and appears to be extending its range rapidly (Moyle 1976). An additional aspect of hitch biology needing to be examined was the extremely high fecundity (112,000 eggs/female) reported by Murphy (1948), which was in contrast to the much lower fecundities (about 3,000 to 26,000 eggs/female) reported by Nicola (1974) for L. e. exilicauda from Beardsley Reservoir, California. The purpose of this study, therefore, was to examine the feeding habits and growth rates of Clear Lake hitch, for comparison with pre-silversides studies, and to reexamine their fecundity. 1 Present address: Dept. Engineering Research, Pacific Gas and Electric Co., 3400 Crow Canyon Road, San Ramon, CA 94584.