Foraging in Non-Native Environments: Comparison of Nile Tilapia and Three Co-Occurring Native Centrarchids in Invaded Coastal Mississippi Watersheds

Abstract

We examined the diet of the alien Nile tilapia and bluegill, redear sunfish, and largemouth bass over a two-year period in coastal Mississippi. Nile tilapia diet was visually separated from the three natives based on group-average linkage cluster analysis. Sequential two-way nested analysis of similarities indicted there was no season effect (Global R = 0.026, P = 24.3%), but there was a moderate size class effect (Global R = 0.457, P = 0.1%) and a strong species effect (Global R = 0.876, P = 0.1%). Pairwise tests indicated species fed on different components of and locations within the environment, with bluegill, redear sunfish and largemouth bass (all R £ 0.683, P = 0.1%) having the most similar dietary components and Nile tilapia (all R ‡ 0.953, P = 0.1%) having the most distinct. Multivariate dispersion indicated that largemouth bass (1.425) and bluegill (1.394) had the most diverse diets compared to redear sunfish (0.906) and Nile tilapia (0.918). Similarities of percentages indicated that diets were separated based on prey: bluegill and redear sunfish consumed chironomids and insects; largemouth bass consumed fish and insects; and Nile tilapia fed most often on sediment resources such as nematodes, rotifers, bryozoans and hydrozoans. Nile tilapia had the highest frequency of mud, sand and detritus in their stomachs, suggesting they fed directly on bottom sediments. These data and the fact that Nile tilapia has a 1.3-7.6 times longer intestine on average than its body length, support our contention that this alien species feeds at the base of the food web and is well adapted to survive and proliferate in non-native environments.

Infection patterns of Nile tilapia (Oreochromis niloticus L.) by two helminth species with contrasting life styles

“…The positive correlation is explained by parasite accumulation in larger fish due to prolonged exposure and ontogenetic habitat and feeding shifts (Esch and Fernändez 1993;Paperna 1996;Marcogliese 2002). The prey size and diet of O. niloticus changes, although slightly, with size (Peterson et al 2006). This increases the chances of larger fish to ingest infected intermediate hosts.…”

Rapid digestion of fish prey by the highly invasive ‘detritivore’Oreochromis mossambicus

“…The long narrow tilapia gut is characteristic of both herbivore and detritivore fishes (Horn, 1989; Stevens & Hume, 1995) and is thought to increase the retention times and exposure to digestive processes of refractory compounds (German & Horn, 2006). This may also reflect an adaptation to consuming sediments and their contents (Peterson et al , 2006). The presence of cellulases in fish guts is also thought to characterize the diets of primary herbivores and detritivores (Prejs & Blaszczyk, 1977), and Saha et al (2006) described cellulase‐producing bacterial flora in the intestinal tract of O. mossambicus , indicating an adaptation to consuming plant cellulose.…”

A complete chitinolytic system in the atherinopsid pike silverside Chirostoma estor: gene expression and activities

“…In contrast, O . niloticus , which has a very long intestine (1·3–7·6 times its body length; Peterson et al ., ), has very active chitobiosidase and endochitinase activities in the stomach and intestine, but very low NAGase activity (Molinari et al ., ). This suggests that O .…”