engleski

Interactions of native and non-native fishes in eutrophic lakes Bara and Jamarice in Croatia

Ecological impacts of invasive species being prerequisite in recent times due to their most significant threats of local ecosystems, in this study for the first time structure of native and non-native fish species and their feeding interactions of Bara and Jamarice lakes were displayed. Specimens were collected by electrofishing from both lakes of eutrophic character, muddy bottom and surrounded by low aquatic vegetation located in continental part of Croatia in the Sava River basin. The abundance of Jamarice lake was dominated by stone moroko (Pseudorasbora parva) (42.80%) followed by rudd (Scardinius erythropthalmus) (23.8%), pike-perch (Sander lucioperca) (19%) and black bullhead (Ameiurus nebulus) (14.3%). The species composition of Bara lake was considerably different from the former one. Of the overall number, introduced species were dominant, such as pumpkinseed (Lepomis gibbosus) (50.70%), pike-perch (2.9%) and stone moroko (1.41%) ; although in biomass native species were dominated such as roach (Rutilus rutilus) (13%), perch (Perca fluvialitis) (13%), freshwater bream (Abramis brama) (13%), Alburnus arborella (2.9%), ide (Leuciscus idus) (2.9%) and pike (Esox Lucius) (1.5%). To determine the dietary preferences, stomach contents were analyzed and expressed as 27 prey items comprising the most preferable food such as Chironomidae, Oscillatoria, Copepoda, Daphnia, Bosmina etc. Chironomidae has had the most part in the diet of stone moroko and pumpkinseed indicating on food competition with the native species. Perch and roach have showed the higher feeding interspecific competition. The decline in some native fishes was found with the increasing numbers of invading species and the feeding behavior between them.

fish composition; non-native fishes; feeding interactions

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