EFFECTS OF ARTIFICIAL LIGHTING AND PRESENCE OF MENIDIA BERYLLINA ON GROWTH AND DIET OF LABIDESTHES SICCULUS

Abstract

Two atherinid species, Labidesthes sicculus (brook silverside) and Menidia beryllina (inland silverside), often co-occur in North American reservoirs. Menidia beryllina is a superior competitor for zooplankton and has displaced Labidesthes in a number of reservoir habitats. In Lake Texoma (Oklahoma-Texas), Labidesthes was thought extirpated from the reservoir after introduction of Menidia in the 1950s, but several recent populations were discovered in down-lake coves with established marinas. Artificial lighting from marinas might benefit Labidesthes by attracting terrestrial insects in these habitats. We conducted a field experiment to test effects of artificial lighting and abundance of Menidia on growth and diet of Labidesthes. Dry weight of Labidesthes at the end of our experiment was significantly higher in artificially lit treatments than in dark treatments, but there was no significant effect of Menidia abundance on weight of Labidesthes. We concluded this effect was attributed to greater availability of dipterans, which dominated the diet of Labidesthes, under artificial lights. Whereas Menidia is a more efficient planktivore than Labidesthes, increased abundance of dipterans near marinas likely promotes the coexistence of these 2 species. RESUMEN—Dos especies Atero ´nidos, Labidesthes sicculus y Menidia beryllina (charal de marea), suelen co- ocurrir en los embalses norteamericanos. Menidia beryllina es un competidor superior para zooplancton