Whitefish population on Lake Constance: Hope remains, but the situation is critical!

Whitefish population on Lake Constance: Hope remains, but the situation is critical!

There is currently a tense situation for fishermen and the whitefish population in Lake Constance. A fishing ban on whitefish has been in effect since January 2024, which applies equally to professional and recreational fishermen. The International Conference of Representatives for Lake Constance Fisheries (IBKF) issued this ban with the aim of protecting the severely decimated whitefish population after alarm signals appeared in June 2022. At that time, only 21 tons of whitefish were caught by 64 professional fishermen, a decrease of over 80 percent compared to the previous year. 20 years ago the catch was over 800 tons. Petri Heil reports that the causes for this dramatic decline are diverse, including the spread of sticklebacks and quagga mussels as well as increasing pressure from cormorants.

However, current studies also show bright spots: a series of studies by the Fisheries Research Center in Langenargen has found an increase in the whitefish population and an improvement in food quality. Despite these positive trends, the situation remains critical. The fishermen complain about empty nets and report skinny whitefish because they can hardly find any food in the cleaned Lake Constance. The fishermen are demanding re-enrichment with phosphorus, which was rejected by the International Water Protection Commission. Schwäbische points out that the intensive cleaning of the lake since the 1970s has ensured excellent drinking water quality, but is also responsible for a shortage of food resources for the fish.

The threats to the whitefish

In addition to feeding challenges, the invasive species are causing headaches for fishermen. The stickleback, which has been spreading in Lake Constance since 2013, eats whitefish larvae and their eggs. The quagga mussel, first spotted in 2016, also competes for food in the lake, which further worsens the situation for the whitefish. During the current three-year fishing ban, the high stickleback population is intended to be reduced, while stocking fish will only be introduced next spring when they are large enough for the sticklebacks to no longer eat. Petri Heil also reports that additional types of nets are permitted in order to diversify fishing species such as roach, perch, pike and catfish.

Looking ahead, it remains to be seen how much of an impact the fishing ban will have on the whitefish population. The long-term effects will not be visible until the end of 2026 at the earliest. The hope for recovery lies not only in protecting the whitefish, but also in checking food resources and the phosphorus issues already mentioned. There is lively discussion in fishing circles as to whether eliminating high levels of phosphate removal in sewage treatment plants could improve the growth situation of whitefish. Protective measures against cormorants are also repeatedly called for, as they represent one of the main threats to fish stocks. Ultimately, the situation for Lake Constance fishermen remains tense, and their calls for alternative courses of action are becoming louder and louder.