Food habits and abundance of larval freshwater drum in a South Central Nebraska irrigation reservoir

Abstract

During certain times of the year high densities of larval fish can impact the aquatic community. The specific role of freshwater drum (Aplodinotus grunniens) is not known but larval freshwater drum can be abundant in some systems and have been shown to feed on zooplankton. To assist with understanding the role larval freshwater drum play in reservoirs, we investigated changes in peak abundance from 2003–2010 in addition to food habits and prey electivity in 2008 in a South Central Nebraska reservoir. We found that larval freshwater drum abundance varied 100-fold during this study. Cladocerans were an important food item for larval freshwater drum. Freshwater drum >10 mm total length selected for Daphnia spp. (46–80 % of organisms found in stomach), while freshwater drum ≤10 mm total length selected for Bosmina spp. (37% of organisms found in stomach), which is a less common group of zooplankton in this reservoir. All larval freshwater drum showed a negative selectivity for copepod nauplii (the Strauss index value of ≤−0.35 for all length groups). Based on the food habits described in this study, larval freshwater drum have the potential to compete with larval sport fish species for desirable zooplankton (ie, Daphnia spp.).