engleski

STRUCTURE AND CHARACTERISTICS OF THE FISH COMMUNITY IN THE NERETVA DELTA (CROATIA) AFTER THE INTRODUCTION OF LARGEMOUTH BASS, Micropterus salmoides (Lacepède, 1802)

Invasive species are one of the leading causes of biodiversity loss. Sport fishermen have recently introduced the largemouth bass (Micropterus salmoides) in the Neretva delta, which raises great concern about the possible impact on the endemic ichthyofauna. Largemouth bass has been introduced to many regions and countries due to its extreme popularity as a species for sport fishing. As early as 2011, it was discovered that in the streams and rivers of Spain and Portugal, it can adapt its eating habits allowing it to be a successful invasive species even in relatively stable aquatic food webs. Its reproductive traits, such as early maturation, relatively high fertility, group spawning, and parental care, are believed to facilitate successful settlement in various conditions. The largemouth bass was first recorded in the Neretva delta in 2016. Individuals reach sexual maturity in the Neretva delta at the age of one year. Spawning takes place in spring when the water temperature reaches 15.5˚C. The difference in the structure and abundance of the fish community after the invasion of largemouth bass in the Neretva delta habitat was investigated. Changes in stable food chains, reduction or disappearance of indigenous ichthyofauna, evident plasticity of the diet, as well as changes in the composition of benthos have been found in many places. The greatest issue in verifying the differences before and after largemouth bass introduction is information about the previous state of the ichthyofauna. In the case of the Neretva delta, we have had a good analysis of the ichthyofauna available twenty years before the invasion. In the year 2004 a field research in the lower course of the Neretva River and its tributaries, on the border of fresh and brackish biotopes, has recorded 38 fish species, of which 30 species are native and eight species are alien. The identified fish belong to 22 families, with the most numerous being the family Cyprinidae with 18 species, followed by the family Salmonidae with six species, Gobiidae and Mugilidae each with three species, and Petromyzontidae and Percidae each with two species. The remaining families are represented with only one species. In comparison with previous results, this study indicates that the number of most small fish species has drastically decreased.

alien species, invasive species, fish community, introductions of new species

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