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Doctoral thesis, 2002

Thermal performance of Arctic charr : intraspecific variation and competitive ability

Larsson, Stefan

Abstract

Under experimental conditions, I have studied and compared the thermal performance of several geographically separated wild Arctic charr populations. In addition, I have studied the preferred temperatures of charr and brown trout. Fish were reared both singly and in groups. The data were analysed and fitted to baseline models in order to estimate the growth efficiency as well as the lower, the upper and the optimum temperatures for growth and feeding of charr. Overall, the optimum temperature for feeding and growth of charr was found in the range 14-17°C and only slight differences was found between populations. The lower and upper limit for feeding and growth were estimated at about 2-3°C and 21-22°C, respectively. The upper limits and the optimum temperatures for growth and feeding are clearly higher than suggested in previous studies. The unexpected high lower limit may result from fish being acclimatised to summer conditions and the rather short (14 days) experimental periods. Charr had remarkably high growth efficiency that varied between 40-60%. The growth efficiency was only moderately affected by temperature. The preferred temperature of charr was found to be 11.4°C, which is about 3.5°C lower than the temperature for maximum growth. This was significantly lower than for trout, which selected a temperature of 16.0°C. Thus, charr thermoregulation strongly contradicts the general rule of coincidence of preferred temperature and optimum temperature for growth of fish, while brown trout obeys it. This finding might partly explain why charr and trout are niche segregated, when they exists in sympatry. The summer temperature in the littoral of lakes containing sympatric charr and trout generally exceeds the preferred temperature of charr, which then will move to cooler and deeper areas. Today, the Arctic charr in Scandinavia appears to be on the southern edge of its distribution. Perturbations of the thermal environment of charr (e.g. hydroelectric power plants, nuclear power plants or forestry actions and global climate change) might escalate the erosion of charr habitats. The findings of this study can be used as a tool in order to identify and manage threatened habitats and populations. Furthermore, this basic knowledge of the thermal performance of charr could be used to improve the management of charr under farming conditions.

Keywords

thermal adaptation; Salvelinus alpinus; Salmo trutta; growth model; diet; food conversion; thermal limits

Published in

Acta Universitatis Agriculturae Sueciae. Silvestria
2002, number: 251
ISBN: 91-576-6335-1
Publisher: Swedish University of Agricultural Sciences

Authors' information

Swedish University of Agricultural Sciences, Department of Aquaculture

UKÄ Subject classification

Fish and Aquacultural Science

URI (permanent link to this page)

https://res.slu.se/id/publ/107404