Relationship between Spring Snow Depth and Growth of Brown Trout, Salmo trutta, in an Alpine Lake: Predicting Consequences of Climate Change

Abstract

Growth of brown trout in the alpine lake Litlosvatn, 1172 m a.s.l. on the Hardangervidda mountain plateau in western Norway, has been studied in relation to annual variations in accumulated spring snow and date of ice-breaks during the period 1991–1998. The annual growth was negatively correlated with the spring snow depth. During the years 1992–1995, a period with mean spring snow depth at 275 cm, the observed average annual growth of the age-classes 6–8 was 3.5 cm, or a reduction of about 50% compared to years with much less snow in spring (1991 and 1996). Average spring snow depth during the period 1990–1999 was 220 cm, while the average for the period 1930–1979 was 169 cm. A further increase in winter precipitation, resulting in even more accumulated spring snow compared to the 1990–1999 level, would result in further reduction in growth of brown trout in the lake. Thus, the present catchable size of brown trout would probably not be reached, due to increased population density and an additional density dependent growth. A climate change, resulting in more snowfall in the whole alpine region of West Norway, as predicted by climate models, may therefore have an important negative effect on fish production and fisheries in a whole region.