Background. Fish introductions have been a common tool to increase efficiency of utilization of water bodies and diversification of aquaculture production. As a result of increased interest in aquaculture and recreational fishing, throughout the past 70 years, the number of non-native fishes in Bulgaria has dramatically increased. This paper reviews the history, current state, and tendencies of the fish introductions in Bulgarian freshwaters. Materials and methods. The statistical data about introductions and aquaculture production were provided by the National Agency Fisheries and Aquaculture (Ministry of Agriculture and Forestry). A part of the data for restocking activities was provided by Bulgarian Union of Hunters and Fishermen. The taxonomy of freshwater fishes was based on the review of Eschmeyer (2006). Results. At present, twenty-six exotic species have been intentionally or unintentionally introduced in Bulgarian inland waters. They represent 15% of Bulgarian′s freshwater fish fauna and provide more than 60% of aquaculture production. The most abundant are exotic cyprinids (Cyprinidae) and salmonids (Salmonidae), constituting 22% and 18% of all introductions, respectively. The most intensive import of non-indigenous fishes, namely East Asian herbivorous carps (Cyprinidae), into Bulgaria occurred in the middle of the 1960s. Only twelve species have been naturalized. Two of them (Lepomis gibbosus and Perccottus glenii) are considered invasive. Along with these fish introductions, parasites, bacterial and viral pathogens were imported. Conclusion. The results of different fish introductions into Bulgarian freshwaters are controversial. Along with the positive influence on the aquaculture development, some extremely negative consequences, such as introduction of pathogens and spread of invasive species were observed. New introductions of fish species should not be made without scientific analyses evaluating the potential effects of introductions. Research, education, and strict control are the key tools of any effort to prevent the spread of the alien fish species.

introductions, freshwater fish, Bulgaria, legislation