Life History Dynamics of Menidia beryllina from Lake Texoma

Abstract

Life history calculations for Lake Texoma Menidia beryllina (Cope) show that female fecundity is size-dependent with egg numbers ranging up to ca. 2000 eggs per female per day of a 3-month breeding period. During that time female growth cannot be demonstrated and extensive mortality results in virtually no adults surviving to spawn a 2nd year. Growth is density-dependent and reproduction can occur if youngof-the-year achieve minimum spawning size before water temperatures exceed the maximum breeding limit of ca. 30 C. INTRODUCTION Detailed life-history summaries are available for few fishes, especially for small species with short life spans. Substantial background information is available on feeding and reproduction that can facilitate life-history calculations for Menidia beryllina (Cope) inhabitating Lake Texoma. Most of the published reports on Menidia in Lake Texoma reference the Mississippi silverside (Menidia audens); however, Chernoff et al. (1981) demonstrate extensive integration with the tidewater silverside (Menidia beryllina). I agree with their conclusion that the two morphs are conspecific and use the latter name to comply with scientific name priority. Lake Texoma was formed by Denison Dam in 1942 and filled to power pool level in 1945. At this level, the lake has a surface area of 36,000 ha and a shoreline of 933 km (Patten et al., 1975). When first filled, Lake Texoma had dense populations of the brook silverside (Labidesthes sicculus). The first reported collection of Menidia in Lake Texoma was in 1953 (Riggs and Bonn, 1959). By 1955 Menidia had attained population densities equivalent to those of Labidesthes in earlier years. It seems apparent that Menidia were inadvertently released into Lake Texoma in the early 1950s from an unknown source. This hypothesis of introduction is supported by the first known occurrence of Menidia in Oklahoma in 1949 (Moore and Cross, 1950) and by the absence of Menidia at inland locations in Texas prior to 1950 (Bonn and Kemp, 1952). Tilton and White (1964) demonstrate and document a spread of tidewater silversides in the Colorado River Basin in Texas. The Lake Texoma stock of Menidia was the source of the silversides stocked into Clear Lake, California (Carl D. Riggs, pers. comm.). Food habit studies by Saunders (1959), Elston and Bachen (1976) and R. Drenner (pers. comm.) have shown that the Lake Texoma stock of Menidia feeds extensively on copepods, cladocerans and chironomids. Elston and Brachen (1976) reported they feed mostly during daylight hours (0700-2000 hr) in August and they suggested a 1-hr stomach retention time. If so, they have ca. 14 daily feedings. If those feedings average only 1 % of total biomass, a daily ingestation of 14% of the biomass occurs. Observations during May, June and July 1980 (the Lake Texoma breeding period) suggest more nighttime feeding by Menidia (Michael Bleakley, pers. comm.).