Shark alarm in Lake Constance? Cuddly toy causes a sensation!

Shark alarm in Lake Constance? Cuddly toy causes a sensation!

On September 23, 2025, an eerie observation in Lake Constance caused a stir: a dark shadow in the water led residents and swimmers to suspect that a shark might be in the region. But the all-clear quickly followed when an attentive passerby revealed the supposed predator to be a harmless cuddly toy that was fished out of the water by a woman from Constance. This bizarre situation raised the question of whether sharks like the bull shark (Carcharhinus leucas) could theoretically live in Lake Constance.

The bull shark is a member of the requiem shark family and is known to thrive in both saltwater and freshwater. This extraordinary ability to osmoregulate allows sharks to regulate their salt balance, which also allows them to survive in rivers and lakes. In fact, bull sharks have been observed in waters such as the Mississippi, the Amazon, and the Zambezi, with them even being spotted in Gulf ponds in Australia. They also climbed numerous rapids in Lake Nicaragua via the Río San Juan and found a home there.

How dangerous are bull sharks?

Bull sharks reach a considerable size: females can grow up to 3.5 meters long, while males can reach around two meters. These sharks prefer shallow water, especially near the banks and at the mouths of rivers. They are opportunistic predators that hunt in murky water and are considered a threat to humans, especially in the summer months where they are responsible for many shark attacks. A total of 75 unprovoked attacks were documented, including 23 fatal incidents.

The appearance of the bull sharks is striking: gray-greenish in color with a white underbelly, they appear beefy due to their stocky body and wide snout. Their characteristic features include the almost rectangular dorsal fin and the absence of the interdorsal ridge. However, in the current discussion about safety in Lake Constance, the danger posed by bull sharks remains unfounded for the time being. Since Lake Constance is not connected to the oceans via major river systems, the risk of this shark species colonizing is extremely low.

Population status and importance of the bull shark

Despite their adaptability, bull shark populations are endangered worldwide. Experts estimate stocks are down by 30 to 50 percent, mostly due to habitat loss and overfishing. In Costa Rica, protective measures have already been taken to stabilize the populations again. Current challenges include, but are not limited to, the long-term recovery of stocks, which could potentially take 20 years or longer.

In summary, this incident in Lake Constance not only provides a dose of thrills, but also stimulates discussion about the settlement and protection of sharks in our waters. As we swim in the blazing waters of Lake Constance on hot summer days, we should be aware that marine ecosystems and their inhabitants, such as the bull shark, need our protection and play an important role in preserving biodiversity.