4.5 Article

Small but voracious: invasive generalist consumes more zooplankton in winter than native planktivore

Journal

NEOBIOTA
Volume 78, Issue -, Pages 71-97

Publisher

PENSOFT PUBLISHERS
DOI: 10.3897/neobiota.78.86788

Keywords

Bythotrephes longimanus; Lake Constance; overwintering strategy; pelagic whitefish diet; planktivory; predator size; seasonal prey selection; stickleback invasion

Funding

  1. Deutsche Forschungsgemeinschaft (German Research Foundation) [298726046/GRK2272]
  2. Bavarian State Ministry of the Environment and Consumer Protection
  3. Public Scholarship, Development, Disability and Maintenance Fund of the Republic of Slovenia [11013-8/2021]
  4. grant SeeWandel: Life in Lake Constance -the past, present and future by the European Regional Development Fund
  5. Swiss Confederation

Ask authors/readers for more resources

In recent years, Lake Constance has been invaded by the three-spined stickleback, which has led to a decline in the native whitefish population. This study compares the diet of the stickleback and the whitefish in different seasons, and evaluates the threat of the stickleback invasion on the whitefish population. The results show that, despite their small size, sticklebacks can be serious competitors to native planktivorous fish.
In recent years, Lake Constance has experienced an invasion and domination of three-spined stickleback (Gasterosteus aculeatus) in the pelagic zone, which has coincided with a decline in the native whitefish (Coregonus wartmanni) population. Similar massive invasions of sticklebacks into pelagic zones have been recognized also in marine areas or small lakes worldwide. However, their diet overlaps with native species is rarely evaluated, especially in the winter season, which often presents a bottleneck for fish survival. In this study, we compared the diet of pelagic sticklebacks with the diet of the substantially larger native whitefish in different seasons, to evaluate the threat of the recent stickleback invasion on whitefish populations. By monthly sampling of zooplankton and both fish species diets, we could demonstrate that sticklebacks select similar prey throughout most of the year and consume more prey than whitefish during the winter. With relations between prey availability and prey selection, interspecific and intraspecific seasonal diet variability and indices like a prey-specific index of relative importance, we discuss the importance of zooplankton species traits and abundance for whitefish and stickleback predation. This study shows that sticklebacks, despite their small size, represent a serious potential diet competitor to native planktivorous fish. Sticklebacks quickly adapt to new environments, and thus we advocate precautions regarding their introduction into similar lakes as Lake Constance, as this could cause irreversible ecological changes.

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