engleski

FOOD WEB STRUCTURE AND FISH COMMUNITY RELATIONSHIPS IN PLITVICE LAKES NATIONAL PARK

Plitvice Lakes National Park in Croatia represents an ecologically significant example of a karstic dominated ecosystem. Despite its recognition as a UNESCO World Heritage site and its consequent protection, the aquatic environment continues to experience anthropogenic disturbances in the form of water quality deterioration and non-native species introductions (primarily European chub). The objectives of this study were to use stable isotope analysis to establish food web structure, and to identify important food sources and potential dietary overlap between native and non-native fishes. Representative members of the fish community, benthic macroinvertebrates (BMI), zooplankton, macrophytes, mosses, and terrestrial leaf litter were collected from two lakes (Prošće and Kozjak) in Plitvice between June and October of 2017. Samples were subsequently oven-dried prior to carbon and nitrogen stable isotope analysis. Results indicated that the food web structure in both lakes was very similar. Benthic littoral production, likely from allochthonous leaf litter, appears to be the primary energy source. Most BMI and fishes had carbon isotope ratio values between -30 and -35‰ indicating that the fish were primarily eating BMI with plankton contributing relatively little to fish biomass. Native brown trout and pike were the top predators in each lake, and isotopic signatures indicated strong dietary overlap with European chub

web structure, fish community, Plitvice lakes

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