The amazing trout of Lac Leman


Trout might be in the salmon family, but the two fish have fairly distinctive behaviours. Trout tend to get territorial in rivers and lakes, while salmon start in rivers, head to sea and then head back upriver to spawn, leaping spectacularly upstream and sometimes into the mouths of waiting grizzlies.

Lac Leman (Lake Geneva) is no sea, but it is pretty big, and it grows big trout. And low and behold, come the beginning of winter these trout head upstream leaping through the rough water of the short Jura streams like packs of salmon. No grizzlies, but at the Aubonne River weir they are likely to to encounter fishers dreaming of defying the out of season timing or all this leaping or photographers rising to a different challenge.

The photography challenge

The leaping trout of Lac Leman

And a difficult challenge it is too. These fish erupt suddenly from the water and move very fast - movement blur at 1/3200 of a second is not unheard of. To get that speed, you are playing with wide open apertures and narrow depths of field, so you are not always focussed on the right bit of stream when a fish emerges and you jab the button.

A mystery


But there is a mystery involved. Rivers like the Aubonne are already full of trout, as far as can be discerned, of identical species to the lake trout. These river trout behave like any other river trout and stay put, letting their generally larger cousins migrate back and forth from lac to upstream and back over the top of them.

A couple of fish biologists are pondering the issue. Check back later and we might have a bit more detail on their ponderings.