Desperate times call for desperate measures, and fish that would not normally eat other fish will do so to survive, according to research to be published in a forthcoming issue of the Journal of Fish Biology.
The study by researchers from Norway and Russia studied the Vendace (Coregonus albula), an invasive species in Lake Ruskebukta in Norway.
The Vendace invaded the subarctic Pasvik watercourse in the border area between Norway, Russia and Finland (of which Lake Ruskebukta is a part) during the early 1990s after having been introduced to a tributary in about 1960. In much of the Pasvik watercourse as in elsewhere in its native range, the Vendace is known as a specialised feeder on zooplankton, but Sibylle Liso and co-authors demonstrate that the alien population in Lake Ruskebukta is capable of feeding on other fishes.
The authors caught 125 fish from the lake using multimesh gillnets and examined their gut contents. They found that other fishes (predominantly the Nine-spined stickleback Pungitius pungitius) constituted nearly 20% of prey abundance in the guts examined, and were found in 14% of the fish sampled. Surface insects also constituted a large proportion of the species’ diet (60% of prey abundance).
The authors hypothesised that the Vendace is eating fishes in Lake Ruskebukta, because an explosive increase in the numbers of the introduced species in the 1990s caused a rapid depletion of zooplankton. This caused the Vendace to switch to a diet consisting of predominantly insects and fish.
This ability to rapidly switch its diet may be the reason for the species’ continued success as an invader in this case, added the authors.
For more information, see the paper: S. Liso, Gjelland, KO, Reshetnikov, YS and P-A Amundsen (2011) A planktivorous specialist turns rapacious: piscivory in invading vendace Coregonus albula. Journal of Fish Biology DOI: 10.1111/j.1095-8649.2010.02831.x