Sommen charr

[2] Survival of Arctic charrs at the southern edge of their natural range is explained by Lake Sommen having a great depth (53 metres (174 ft)) with cold and oxygen-rich bottom waters.

[2] Sommen charr may also draw benefits from the lake's richness in fish species and the complex ecology it implies.

[3] Lek locations lie chiefly along the eastern shores of Norravifjärden and around Malexander in the north-central parts of the lake.

[3] Studies have shown that the substrate in most lek places is bedrock, boulders, gravel and pebbles while only a minority are on sand.

[3] Other nearby populations of Arctic charr are found in the lakes Vättern, Ören and Mycklaflon.

[5] Albeit experiments show that at low temperatures (4 °C (39 °F)) Arctic charrs from more northern lakes grow faster.