Was there a mass extinction? Actually dominant fish species disappears from Lake Constance

At the beginning of the year, 90 percent of the fish in the open waters of Lake Constance were sticklebacks: Now the species has suddenly almost disappeared. Nobody is really sad about it, but the exodus is still a mystery.

The sticklebacks seem to be disappearing from Lake Constance. During a stocktake in the lake, researchers found only a few specimens of the fish that had made up the majority of the fish in the open waters of Lake Constance for years.

"We caught hundreds of sticklebacks during the last fishing trips, but now there are less than 50 in total," said Alexander Brinker, head of the fisheries research center in Langenargen, Germany.

The small silver fish with the scientific name Gasterosteus aculeatus was first recorded in Lake Constance in the early 1950s. From 2012, it had multiplied explosively and, according to the fisheries research center, still accounted for more than 90 percent of the fish in the open water at the beginning of the year.

And that is actually a problem. The stickleback eats the plankton of the whitefish native to Lake Constance and also preys on their eggs and larvae.

Cause unknown

The scientists cannot really explain the initial results of their inventory. Nothing pointed to a mass fish death in Lake Constance, said Brinker. A disease or a parasite are conceivable causes.

Neither researchers nor fishermen mourn the huge numbers of three-spined sticklebacks in Lake Constance: The species, which was probably introduced into the lake from aquariums, had been causing an imbalance in the ecosystem for years. The population of whitefish, which are actually the flagship species in Lake Constance, continued to decline.

"If the mass disappearance of sticklebacks is confirmed, this could be a real game changer for the recovery of whitefish stocks," said Brinker. The inventory already shows that the whitefish are doing somewhat better: "They no longer look so emaciated."

SDA