Food Selectivity of the Black Bullhead (Ictalurus melas, Rafinesque) in Lake Poinsett, South Dakota

The food habits of young-of-the-year, subadult and adult black bullheads were studied in Lake Poinsett, South Dakota, from March, 1970, to April, 1971. Two hundred twenty young-of-the-year (37-87 mm total length) fed primarily on limnetic cladocerans and copepods. Leptodora and Diaphanosoma comprised 86.5% of the total food volume. Chironomid larvae and pupae made up 5.6% of the total. Other benthic organisms and littoral cladocerans together contributed less than 1%. Stomach contents of 608 subadult and adult black bullhead (143-304 mm total length) indicated significant seasonal vairaiton in diet. Daphnia pulex and chronomid larvae were important food items in winter. Bullheads fed primarily on chironomid pupae. Dphnia pulex, and crayfish, in the spring. Fish and Leptodora were the principal organisms consumed in summer and fall. Food selectivity of young-of-the-year and adult bullheads for seven major species of zooplankton and adults for five categories of benthos was determined using the index described by Ivlev (1961). Adults and young-of-the-year positively selected limnetic cladocerans. Selections was greatest for leptodora and Daphnia pulex. Copepods were least selected by bullehads of all age groups. All chironomid larvae were negatively selected by adult bullheads while chronomid pupae (99% Chironomus spp.) were strongly selected (+0.75). Selectivity index for all organisms appeared to be dependent on their abundance, size, degree of exposure, and ability to avoid ingestion either by outmaneuvering their predators or by retreating into the bottom sediments

Food and Food Selectivity of the Black Bullhead, <i>Ictalurus melas</i>, in Lake Poinsett, South Dakota

Food habits and food selectivity of the black bullhead (Ictalurus melas) in Lake Poinsett, South Dakota, were studied from March to November 1970. The black bullhead preyed upon a wide range of food sources in the limnetic, littoral, and benthic zones and seasonal differences in diet occurred in response to availability of prey species. The total food volume in stomachs of 558 black bullheads (143–304 mm total length) comprised about 32% planktonic crustaceans, 25% chironomids, 27% fish, 9% crayfish, 2% filamentous algae, and 5% miscellaneous organisms. Planktonic crustaceans made up 94.4% and chironomids made up 5.6% of the volume of food ingested by 220 young-of-the-year black bullheads. Black bullheads were most selective for the largest cladocerans available, Leptodora kindtii, Daphnia pulex, and D. galeata mendotae, and for Chironomus spp. pupae. Black bullheads were least selective for Diaphanosoma leuchtenbergianum, copepods, and chironomid larvae. The black bullhead in Lake Poinsett was primarily a selective planktivore throughout its life history. </jats:p