Prey preference for Asian carp and soft plastic lure ingestion by largemouth bass

Invasive bighead (Hypophthalmichthys nobilis) and silver carp (Hypophthalmichthys molitrix) have become established throughout much of the Mississippi River basin. In many areas, these two species comprise a significant proportion of the fish biomass. Despite their prevalence and potential for negative environmental impacts, to date, there has been no assessment of vulnerability to predation of Asian carp compared to native species. We sought to examine largemouth bass (Micropterus salmoides) predation on juvenile bighead and silver carp in relation to common native prey species. Prey species selection experiments in 2-m pools showed number of prey captures was highest for bighead carp followed by gizzard shad with lower capture rates for bluegill, golden shiner, and silver carp. Observations of prey and predator behavior were quantified in a 720-L aquarium and variation in anti-predator behavior explained relative differences in vulnerability to predation. Differences in vulnerability to predation may explain the greater invasion success of silver carp. Similar or higher vulnerability to predation of Asian carp compared to common native prey suggests that they may serve as viable prey for native predators mitigating the potential negative impacts on the native prey community. Soft plastic fishing lures (SPLs) have recently gained attention as a potential source of pollution in aquatic systems. A number of anecdotal reports have suggested that discarded SPLs are being ingested by wild fish and causing health problems including mortality. Few studies have been conducted concerning the effects of SPLs on fish. We designed a laboratory study to determine the effects of ingestion of three different shapes and two different materials of SPLs on consumption by largemouth bass. No effects on consumption were observed except on the first day after SPL ingestion. In three trials with 30 fish, all largemouth bass were ultimately capable of expelling the lures from their bodies. Field data were also utilized to determine the occurrence of SPL ingestion by largemouth bass in the wild. In two Illinois lakes, occurrence rates of SPL ingestion were < 1%. Bass sampled with SPLs in their stomach did not have significantly different body condition from fish that had not ingested SPLs. We conclude that discarded SPLs do not pose a significant threat to the health of largemouth bass. Nevertheless, we encourage efforts to responsibly dispose of SPLs in order to prevent pollution and any possible undiscovered consequences of their presence in the environment