Rehabilitation and management of stunted fish populations

Many lakes in northern Norway harbour fish populations that suffer from overpopulation and stunting, having a high density of slowly growing, skinny and highly parasitized fish. This situation is particularly common in lakes with Arctic charr or whitefish populations, and several ecological processes that are related to this phenomenon have been explored through our investigations. Whole-lake density manipulations of fish populations have been central in these studies, which have integrated large-scale ecological experiments with practical fish stock rehabilitation and management.

Long-term ecological studies have been implemented in relation to these whole-lake experiments in order to explore the impacts of the intensive stock reductions. The food resource supply of the fish has in particular been addressed, combined with studies of growth, age and size structure, maturation and recruitment. Interactions with other fish species through competition and predation, as well as parasite infection, are central aspects of these long-term studies.

A practical goal is to develop management strategies that may prevent the development of overpopulation and stunting in fish populations. Several sub-projects have been carried out, including also a number of master and PhD projects.