| Abstract [eng] |
At present, one of the main reasons causing the loss of biodiversity is the rapid spread of invasive species. Alien crustaceans constitute more than a half of all known higher crustacean fauna in Lithuanian lakes. Most of them were intentionally introduced to Lithuanian lakes in order to enhanced fish or crayfish production. Although it passed more than 40 years after the initial introductions there are still many unanswered questions in relation to the introduced crustacean’s impact on local communities. The aim of this research was to evaluate the impact of alien peracaridans on fish diet and growth in lakes, to explore the trophic position of the alien higher crustaceans and to assess the impact of these crustaceans on the lake food web structure. Results showed most of alien crustacean species relied on the littoral carbon source and occupied the transitional position between the typical second and third levels in the lake food chains. Therefore, these species should be considered as omnivorous species in the lake littoral zone. Finally, this research showed alien crustaceans indeed influenced the feeding niche structure of benthic macro invertebrate assemblage in lakes. However, the feeding niche structure of fish community was not influenced by these crustaceans; it was more associated with abiotic factors, such as size, average depth or trophic status of a lake. Although the perch assimilated the introduced peracaridans into its diet, as did some other fish species feeding in the littoral zone, the collation of available data does not support the enhancement of perch and other fish production in Lithuanian lakes. Thus, the original rationale for introduction of the Ponto-Caspian peracaridan species into Lithuanian waters appears misguided. |
