La Grand Assiette de Lac Léman

Lake_Geneva_Sept13

Lake Geneva / Lac Léman from the marina at Thonon-les-Bains in the early morning.

From Lyon, I travelled about 200 km along the course of the Rhône to Thonon-les-Bains, a resort beside Lake Geneva (“Lac Léman” in French) to join a meeting of diatom specialists.  There are few more appropriate places for me to give a talk on the need for intercalibration as we were just 500 metres or so from a large water body shared by two countries.   And this is not just a theoretical exercise as the many restaurants bordering were proudly serving lake fish.   Management of the lake, therefore, has direct consequences for local livelihoods.

Remember, too, that this lake is bordered by some large communities, most notably Geneva itself (just under 200,000 people), so there have been substantial inputs of pollution over the years.   As far back as 1880 Switzerland and France shared a common fisheries management policy but this broke down in 1911, after which a combination of overexploitation and pollution hit the fisheries hard.  Indeed, the most highly-prized fish in the restaurants in Thonon-les-Bains was “fera”, a member of the genus Corygonus, a member of the salmon family that is found in only a few lakes in the UK.  Corygonus fera, which was indigenous to Lake Geneva is, in fact, thought to be extinct.  It had a very distinct habitat in the deeper waters of the lake but as pollution increased, so the oxygen levels in these regions decreased.

Pollution levels have now decreased again and, since 1980,  Switzerland and France again have an agreement on management of the fishery.  The fera we were eating last week was a testament to the success of this policy.   It was not C. fera, but a close relative that had been introduced. The sheer quantity that was available around the lake suggests a highly productive fishery although it did lead me to wonder whether this would be sustained if the lake quality continued to improve.

Grand_Assiette_Lac_Leman

La Grand Assiette de Lac Léman from Le Beau Rivage restaurant in Thonon-les-Bains, featuring a salmon tartare, smoked fera and a mousse also made from fera.  Plate of frites just visible on the right hand side of the picture and a glass of Chimay behind.

Think of the pollution in the lake as being equivalent to the manure you put on your garden.   In the lake this “feeds” the algae which, in turn, are eaten by the zooplankton, the main food of Corygonus.   If there is too much pollution/manure, the lake/garden suffers as the bacteria suck the oxygen out of the water/soil.   However, if lake / garden had just the “natural” nutrients, there would be a much lower quantity of produce available for the fishermen / gardener to remove.   Somewhere in between, there is a state with just enough nutrients to support a productive fishery / garden.  It may not be “natural”, but it does represent a balance, of sorts, between nature and economy.  I can’t, in other words, extol the beauty of the environment, and the virtues of conservation and, simultaneously, praise the local delicacies without at least a minor twinge of conscience.

References

Buttiker, B. (2005). Evolution of fish and crayfish, and of fishery in Lake Geneva.   Archives des Sciences 58: 183-191.

Laurent, P.J. (1972). Lac Léman: effect of exploitation, eutrophication, and introductions on the salmonid community.   Journal of the Fisheries Research Board of Canada 29: 867-875.

Lake Geneva / Lac Léman also feature in William Boyd’s recent novel Waiting for Sunrise.

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