Fishing - Stickleback invasion in Lake Constance: initial explanations
The stickleback is considered the enemy of the endangered whitefish in Lake Constance because it has long since left the shore area and now lives in the open water of the lake. There it finds a better food supply, as the Langenargen Fisheries Research Center (FFS) announced on Wednesday. The result: in the open water, the stickleback competes with the whitefish for food and eats their offspring.
A study by the FFS in collaboration with the Technical University of Munich has now investigated the question of why the sticklebacks once left their long-established territory. Sticklebacks from the open water are significantly better supplied with long-chain omega-3 fatty acids than their conspecifics on the shore. The explanation for this lies in their diet, as the sticklebacks in open water can eat significantly more copepods, which in turn contain high amounts of these important fatty acids.
Shore sticklebacks, on the other hand, have to increasingly switch to water fleas, which are deficient here, according to the press release. The food in the open water is therefore of significantly higher quality and offers a plausible explanation for the extremely unusual migratory behavior of sticklebacks in Lake Constance.
The scientists also provide an answer to the question of why such an invasion of open water has only been described for Lake Constance so far. "The sticklebacks in Lake Constance, which were introduced by humans, are of marine origin," Jan Baer from the Fisheries Research Center was quoted as saying in a press release. In the sea, these omega-3 fatty acids are almost abundant in food. In fresh water, however, the situation is different, as certain essential fatty acids are unevenly distributed. "This is probably the reason for the migration of the Lake Constance sticklebacks into open water, as they can reach the important omega-3 fatty acids much better there," concluded Baer.
According to the press release, the sticklebacks only moved into open water in 2012. There is also an explanation for this: at that time, the density of fish in the open water, especially whitefish, was unusually low and competition for food and space in the open water was low. The sticklebacks possibly took advantage of this for their invasion and took over the whitefish's habitat, much to their chagrin.
Fisheries Research Center Baden-Württemberg
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Source: www.stern.de
