“Too clean” Swiss lakes threaten fish stocks

The joys of fishing in Switzerland may be compromised by the fall in fish stocks Keystone Archive

Switzerland's annual fish catch has decreased by 10 per cent, despite improved water quality in Swiss lakes. The growing shortage of fish has been blamed on a lack of food for smaller species.

Last year’s fish catch of 1,700 tonnes was down by 10 per cent compared to the past decade’s average results, according to the Swiss Environment Agency.

Fishermen’s earnings also dropped by about one-third in comparison to the 1980s.

Erich Staub, head of the fisheries division at the agency, told swissinfo the decrease in fish had been caused by a lower concentration of phosphates in lakes. The scarcity of the substance, which stimulates the growth of algae, led to the reduction of food for whitefish.

Switzerland’s tighter pollution control laws, which have been applied since the 1970s, are said to be the main reason for change.

“Fifteen years ago, there was a reduction of phosphates in household washing powders, and this brought down the concentration of the chemical in lakes,” Staub said. “This reduction in nutrients also caused a reduction of the fish population.”

However, the agency pointed out that the fish population should soon increase. It said that while some fish, such as roach or tench, are becoming more scarce, others are likely to reappear.

Fritz Hulliger, vice-president of the Swiss Association of Fishermen, agrees with the agency’s assessment of water quality. He says Swiss lakes have become too clean.

“They’ve cleaned our lakes too well,” Hulliger said. “It’s not necessary that you clean all the stuff out of the water.”

However, Staub said the agency had no intention of cutting back on its efforts to control water pollution.

“From the ecological point of view, there’s no intention of going back,” he said. “Fishermen don’t want that situation either.”

The agency’s results are based on a study of fish catches from Switzerland’s 15 largest lakes.

The best catches were made on Lake Biel, with an average of 33 kilogrammes per hectare of lake surface. Lake Thun and Lake Neuchâtel also yielded above average results.

Two-thirds of fish caught in Switzerland last year were whitefish. Perch were the second largest category of fish caught.

swissinfo with agencies