engleski

Status and characteristics of Croatian freshwater fish

The present study describes the status of protection, the structural and temporal abundance of fish communities in Croatian rivers. Data presented are results of surveys made by electrofishing on all major rivers. Zoographically Croatia is divided into two well-separated Danubian and Adriatic watersheds. Knowledge of freshwater fish of Croatia is insufficient despite that biodiversity and the number of endemic forms in the Dalmatian ichthyologic region is one of highest in Europe. Extensive parts of Croatian territory are not included in regular investigations and therefore areas of distribution for many species are still unknown. Some rare and data deficient species, subspecies and races are not described in detail and their ecology is completely unknown. The total number of fish species and subspecies in fresh waters of Croatia is 149. Twenty-one species live in freshwater as well as in saltwater habitats. Over the last decade, six new freshwater fish species have been described, and this number is not final. About 40 fish species are exploited commercially. Fish are influenced by many environmental factors, the most important being pollution, river regulations, damming, introduction of alien species, the huge demand of Croatian society for technical and drinking water, over fishing and tourism. Dams prevent migrations to spawning grounds, increase concentrations of nutrients. Over the last decades many species have disappeared or their populations diminished significantly. About 5 fish species either disappeared from Croatian waters or there has been no data on them for more than 40 years. Thirty-two species are endangered. In the near future they can also disappear if conservation measures will not be implemented. The status and biology of 14 rare fish species are poorly known. One of the most dramatic consequences of human impact on fish is the introduction of alien species in some regions. Fifteen invasive alien species have been adapted to our region. Effects of alien species on native communities are unpredictable.

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