Did a widespread extinction event occur in Lake Constance?
Since the 1950s, the three-spined stickleback became a common sight in Lake Constance. But since 2012, its population has been escalating rapidly. Unfortunately, this once abundant species is now becoming hard to find. Researchers have proposed two potential explanations.
For a considerable period, it dominated the population of free-swimming fish in Lake Constance. However, a recent assessment of the lake revealed a drastic decrease in their numbers. According to Alexander Brinker, lead researcher at the fisheries research station in Langenargen, they caught hundreds of sticklebacks during their last fishing operations, but now there are barely 50 left.
The silver fish, scientifically known as Gasterosteus aculeatus, was first spotted in Lake Constance in the 1950s. Its numbers had been growing exponentially since 2012, making up over 90% of the free-swimming fish at the start of this year. It feeds on the plankton that the native whitefish relies on, and also preys on their eggs and larvae.
Disruptive non-native species
The sudden disappearance of sticklebacks has left researchers puzzled. No signs of a mass fish die-off were found in Lake Constance, said Brinker. Instead, a disease or parasite could be to blame.
Neither researchers nor fishermen lament the loss of the three-spined sticklebacks in Lake Constance. This presumably introduced species has been wreaking havoc on the ecosystem for years. The whitefish population, which should be the dominant species in the lake, has been declining steadily.
"If the decline in sticklebacks is confirmed, this could significantly aid the recovery of whitefish populations," said Brinker. Preliminary data suggests that whitefish are showing signs of improvement: "They no longer look as malnourished."
The three-spined stickleback was once a dominant species in Lake Constance, known for its large population of this fish. However, recent assessments show a striking decrease in their numbers, leading to concerns among researchers.
Despite being a common sight in Lake Constance since the 1950s, the once abundant three-spined sticklebacks are now becoming hard to find, potentially aiding the recovery of the native whitefish population.
