Invasive Species Compendium

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Abstract

Diet composition changes in tigerfish of Lake Kariba following an invasion by redclaw crayfish.

Abstract

The present study used a combination of stable isotope techniques and stomach content analyses to examine the diet and ontogenetic diet shifts of tigerfish, Hydrocynus vittatus, in the Sanyati basin of Lake Kariba, Zimbabwe. We compared tigerfish diet shifts in the presence of an invasive crayfish, Cherax quadricarinatus, with previous studies before invasion. Here, we assessed whether tigerfish now had a preference for C. quadricarinatus leading to a shift in its main dietary food sources from cichlids to crayfish. The dominance of cichlids has remained generally high when compared with historical assessments. Stable isotope analyses showed that tigerfish fed on a variety of food sources including those that may be temporarily unavailable. Results of stable isotope analyses also highlighted that C. quadricarinatus was now becoming an important food source across all tigerfish size classes. In conclusion, tigerfish in Lake Kariba showed remarkable dietary plasticity and ontogenetic shifts, identified by both stomach content and stable isotope analyses.