Abstract
The black bullhead is an invasive species that forms dense populations and has a negative impact on the native ichthyofauna. Recent studies indicate that it is one of the most dominant invasive fish species in Serbian waters. Feeding habits based on stomach contents of individuals caught in Lake Sava were analyzed as a first step towards evaluating its possible negative impact on the native fish fauna of the lake. The following indices for diet analysis were applied: vacuity index, frequency of occurrence, numerical abundance and prominence value. Trophic niche breadth and seasonal trophic diversity were calculated using the Shannon?s index. The diet spectrum comprised 16 different prey categories from five groups: Mollusca, Crustacea, Insecta, Teleostei and plants. Fish were the main prey in all seasons, followed by aquatic invertebrates. Plant material and terrestrial insects were used as food in relatively small quantities. Predation on fish eggs was also detected. Our research confirmed that this species is an opportunistic generalist. An ontogenetic diet shift was also detected. The lowest value of trophic diversity was found in age 1+ individuals (H=1.39), while the highest was found in age 3+ individuals (H=2.00). The widest niche breadth was recorded in spring 2011 (H=2.12).
Highlights
According to the International Union for Conservation of Nature (IUCN) [1], the impacts of non-indigenous invasive species are immense, insidious and usually irreversible, and can be compared to the loss and degradation of habitats on the global scale
Feeding habits based on stomach contents of individuals caught in Lake Sava were analyzed as a first step towards evaluating its possible negative impact on the native fish fauna of the lake
The black bullhead, Ameiurus melas (Rafinesque, 1820), which is native to North America, is one of the most abundant and successful non-native fish species in European freshwater ecosystems [9,10,11]
Summary
According to the International Union for Conservation of Nature (IUCN) [1], the impacts of non-indigenous invasive species are immense, insidious and usually irreversible, and can be compared to the loss and degradation of habitats on the global scale. Freshwater ecosystems are inhabited by many non-indigenous fishes [7], which causes behavioral shifts in native species and completely rearranges food webs, leading to the potential extinction of entire faunas [8]. The black bullhead, Ameiurus melas (Rafinesque, 1820), which is native to North America, is one of the most abundant and successful non-native fish species in European freshwater ecosystems [9,10,11]. Seasonal feeding habits and ontogenetic diet shift of black bullhead (Ameiurus melas) in Lake Sava (Serbia).
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