Great Arctic charr in Lake Vättern
In this research project we study several of the suggested causes for the decline of great Arctic charr, using a combination of field experiments, analysis of historical data and analyses of mathematical models.
Lake Vättern, together with a handful of other south Swedish lakes (e.g. lakes Sommen, Ören och Mycklaflon), is home to a large-bodied form of Arctic charr, called great Arctic charr (Salvelinus umbla). This species matures late and can reach an age of up to 25 years, weigh up to 11 kg and reach a length of 85 cm.
Great Arctic charr is today redlisted as Critically endangered and even though the population in Lake Vättern still is the largest remaining in Sweden, the stock has decreased dramatically since the 1950's when yearly record catches of more than 70 tons were landed by the local fishermen.
Many suggested causes for the decline of the stock have been put forward, among those overharvesting, competition from introduced alien species (such as Atlantic salmon and signal crayfish), environmental toxins, reduced nutrient levels and climate change. In this research project we study several of the suggested causes for the decline of great Arctic charr, using a combination of field experiments, analysis of historical data and analyses of mathematical models.
The knowledge gained can be useful for improving the management of lake Vättern's unique stock of Arctic charr so that the recovery of the stock is ensured.
Tomas Jonsson (Associate professor at Skövde university and researcher at the Swedish university of agricultural sciences)