Swiss native fish in troubled waters

More than half of Switzerland’s native fish species are threatened with extinction or are already extinct within the country’s waters, a new assessment showed Wednesday.

Out of 71 native fish and jawless fish, 34 are under threat of extinction in Swiss waters, like the critically-endangered European eel, and nine are no longer found within Switzerland, the Federal Office for the Environment (FOEN) said.

The study of around 70,000 fish in landlocked Switzerland’s rivers and lakes categorized the native species according to the International Union for Conservation of Nature’s criteria, under which threatened and extinct species appear on the Red List.

The update, completed in 2022, is the first since 2007.

Nine native species have had their domestic threat category raised, including the European eel, the stone loach, and the European grayling.

But there was better news for the common carp, the Wels catfish and the telestes muticellus, which saw their threat category drop.

The number of native species assessed has widened from 55 to 71—including five for which there is insufficient data to make a threat conclusion.

However, the number of threatened species is up from 24 to 34.

“The 2007 Red List already showed a precarious situation for fish,” FOEN deputy director Franziska Schwarz said in the update.

“This revised list unfortunately shows no reversal of the trend: overall, the number of threatened fish species continues to increase, thus contributing to an erosion of fish biodiversity.”

Global warming cited

Switzerland is known for its big lakes like Geneva, Constance, Neuchatel, Maggiore and Lucerne, and rivers like the Rhine, Rhone and the Aare.

The report said human activities were threatening fish, especially water pollution, degradation of habitat and hydroelectricity generation.

Meanwhile global warming and competition from non-native species were also putting on the pressure.

“Considerable efforts” to stop heavy pollution and improve wastewater treatment have had a positive impact, though small rivers in intensive agricultural areas have a lot of micro-pollutants.

The nine native species now considered extinct within Switzerland are the European sturgeon, the allis shad, the huchen, the European river lamprey, the weatherfish, the sea lamprey, the Atlantic salmon, the sea trout, and the Salvelinus neocomensis deepwater trout.

Any European sturgeon caught in the Swiss basins of Lakes Maggiore and Lugano “probably come from fish farms or private ponds in Italy”, the report said.

© 2023 AFP