Intestinal content analyses of pumpkinseed Lepomis gibbosus (Linnaeus, 1785) in five small reservoirs – central Serbia

Abstract

Lepomis gibbosus (pumpkinseed) was first recorded as a non-native fish in Serbia in the 1930s in the Tisza River. The species currently inhabits almost the entire region of the Black Sea basin in Serbia, but has no economic value. The current range of the pumpkinseed covers more than 50% of the total Serbian area and is also naturalised in Serbian waters. The pumpkinseed feeds on bottom fauna, small fish, fish roe and juvenile fish, which together with competition for habitat and spawning sites can have a negative impact on native species. The most common prey of younger specimens is zooplankton, while adult specimens feed on larger organisms such as larvae and pupae of insects, molluscs or crustaceans. The composition of the prey varies seasonally and depends on the composition of the community. The main objective of the study was to analyse the differences in the feeding habits of pumpkinseed in five reservoir. Samples were collected from five reservoirs in central Serbia (<200 asl, Markovačko, Topola, Vlaški Do, Jatagan, Kudreč) using standard electrofishing equipment. All sampled reservoirs had mud substrate, except Jatagan Reservoir, which had gravel substrate. The sampled fish were identified on site based on morphological characteristics using identification keys. The sampled fish were measured using total body length and weight. The total sample consisted of 354 pumpkinseed individuals whose body weight ranged from 3.66–9.52 g and body length from 6.01–8.41 cm. The number of individuals with intestinal content was 282, while the number of individuals with empty stomachs was 72. The following macroinvertebrate taxa were identified during the examination of the gut contents: aquatic insects (Chironomidae, Chironomidae-pupae, Diptera, Ceratopogonidae, Trichoptera, Ephemeroptera, Odonata, Heteroptera, Coleoptera), Gammaridae, Mollusca, Bivalvia, Gastropoda, Nematoda. Undetermined terrestrial insects were also recorded. Most prey were found in the Kudreč Reservoir, and the greatest diversity was in the Topola Reservoir. Jatagan Reservoir had the lowest number of prey items, which may be due to the substrate type. The high number of aquatic insect taxa could be explained by the small surface area of the reservoir and the presence of aquatic vegetation.