Wildlife on the Tour du Mont Blanc: Fish in High Alpine Lakes

Lac Cornu. Fish in high alpine lakes.

Are there any fish in the high alpine lakes? Well yes!

Species that you might see swimming around are:

  • Common minnow – Phoxinus phoxinus
  • Rainbow trout – Oncornhynchus mykiss
  • River trout – Salmo trutta fario
  • Alpine char – Salvelinus alpinus
  • Brook trout – Salvelinus fontinalis

These species are particularly resistant to the intense cold of high mountain lakes. However, the growth of these fish is prevented and slowed down by the low temperatures of the water. After all, fish do not generate body heat, they are directly affected by the ambient temperature. That is why “mountain fish” are generally smaller than lower living specimens of the same species, but the cold-bloodedness also has its advantages. Since fish do not use energy to produce heat, they can survive on a minimal diet and in very difficult circumstances, such as in ice-cold lakes high up in the mountains.

Common Minnow - Phoxinus phoxinus
The Common Minnow, also known as the Phoxinus phoxinus. Photo credit: Adrien Pinot

How did these fish end up in high alpine lakes?

The first thing you might ask yourself when you see a fish swimming around in an alpine lake is: “how did these fish end up at such high altitudes?”. The answer to this question is simple: they have been released by humans. Due to the cold temperatures, fish can’t reproduce at high altitude. There is one exception: only the common minnow can produce offspring. The fact remains however that fish populations in alpine lakes depend on humans for their survival.

So why do humans go through all the effort each year of releasing fish into alpine lakes? Unfortunately, it’s for sport fishing purposes. Although it’s exciting to see fish swimming around when hiking past an alpine lake, the impact that these fish have on the fragile ecosystems in our alpine lakes does raise concerns.

Fish in mountain streams

In mountain stream you can also find fish. Species such as the common minnow, river trout and stone loach (Barbatula barbatula) are common. Thankfully, these species occur naturally in mountain streams and these populations are part of a healthy natural aquatic ecosystem!  

Read more about the lakes and their ecosystems on the Tour du Mont Blanc

Lacs de Chéserys – hotspot for alpine newts

Lac du Golliet – hotspot for dragon flies

Aguilles Rouges nature reserve – 22 lakes with unique aquatic ecosystems

Read more about wildlife on the Tour du Mont Blanc

Top 5 species


Reptiles and Amphibians

Simone van Velzen

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