Invasive Species Compendium

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Abstract

Seasonal abundance and feeding patterns of the invasive racer goby (Babka gymnotrachelus) in the littoral zone of a lowland European river.

Abstract

The racer goby (Babka gymnotrachelus), a Ponto-Caspian gobiid, has successfully established in several European rivers since the 1990s, and its range is expanding; however, information on its biology in invaded environments is still limited. Understanding the population dynamics and feeding ecology of this species may assist in predicting its potential impact on native ecosystems. The seasonal abundance and feeding of racer goby were studied in the littoral zone of a lowland river flowing into the Kaniv Reservoir (Dnieper River). The abundance of this goby in the sampling reach displayed significant inter-annual and seasonal fluctuations, which depended on water temperature. Mean lengths of racer goby also varied during the year, and the largest fish were observed mainly in January to April and in September to November. Age-0 fish started appearing in catches at the end of May. Almost all juveniles reached adult size in October of the same year. Overall, 72 prey organisms were identified in the gut contents of racer goby. The most abundant prey were chironomids followed by cladocerans, copepods, and water mites. Chironomids included 25 taxa, the most abundant of which were Polypedilum convictum, Glyptotendipes sp., and Chironomus sp. Among 18 identified cladoceran taxa, the most abundant were Disparalona rostrata, Pleuroxus aduncus, and Alona affinis. Based on the diet composition, which included both bottom-dwelling and macrophyte-associated organisms, it can be concluded that racer goby feeds in a large variety of microhabitats including open non-vegetated areas, on substrates near macrophyte beds, and possibly on macrophytes.