| Summary: | Increasing water temperatures from novel climate change may alter freshwater fish life history strategies, especially those of fish populations in northern latitudes. Fish species life history strategies are reflected by their environments and increasing water temperature may alter the most favorable strategies considering growth and reproductive patterns. In this study, life history traits of a fish community will be investigated to reveal any supposable climate change effects on life history strategies of a subarctic lake in northern Norway. Length, age, and maturity data from three periods of sampling over a 23-year period is used to model and compare changes over time of two life history traits: growth and age-and-size at maturation. The current lake has experienced a community-shift, with decreased relative contribution of the cold-water adapted species Arctic charr (Salvelinus alpinus) and burbot (Lota lota) and a corresponding increase of the cool-water adapted species brown trout (Salmo trutta) and grayling (Thymallus thymallus). At the same time, there has been a mean annual water temperature increase of 1 degree. The growth parameters, L∞ and Gi, are modelled with a modified von Bertalanffy equation. There was in increase in Gi for all species, except for Arctic charr, and an increase in L∞ for all species, except for the burbot during the period of study. These findings suggest that the fish species benefit somewhat of climate change, to this day. The calculated maturation patterns reveal decreased A50 and L50 for both cold-water adapted species, which could indicate a negative temperature effect. The effects of climate change on life history strategies are difficult to distinguish. As there are many factors affecting life history traits in a complex fish community in a heteromorphic lake. Climate change seems to affect life history traits both directly and indirectly through various mechanisms.
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