Latitudinal Variation in Growth of Young Brown Trout Salmo trutta

• Published in: The Journal of animal ecology Vol. 69; no. 6; pp. 1010 - 1020
• Main Authors: Jensen, Arne J., Forseth, Torbjorn, Johnsen, Bjorn Ove
• Format: Journal Article
• Language: English
• Published: Oxford British Ecological Society 01.11.2000; Blackwell; Blackwell Scientific Publications; Blackwell Publishing Ltd
• Subjects: Agnatha. Pisces; Animal and plant ecology; Animal ecology; Animal, plant and microbial ecology; Animals; Autoecology; Biological and medical sciences; British Isles; Denmark; Freshwater ecology; Freshwater fishes; Fundamental and applied biological sciences. Psychology; Human ecology; Marine fishes; Modeling; Norway; Population growth; Population growth rate; Salmo trutta; Spain; Trout; Vertebrata; Young animals; Norway; Europe; Salmonidae; Temperature; Growth rate; Latitudinal variation; Growth; Twilight; Environmental factor; Anadromous species; Corporal biometry; Latitude; Young animal; Vertebrata; Salmo trutta; Migratory; Pisces; Body size; Density dependence; Geographical variation; Adaptation
• ISSN: 0021-8790; 1365-2656
• DOI: 10.1046/j.1365-2656.2000.00457.x

1. A new laboratory-based growth model for brown trout (Salmo trutta) was used to explore latitudinal variation in growth among natural populations. The model included the effects of differences in ambient temperatures and fish size among populations. Annual growth rates of anadromous brown trout parr from 22 Norwegian populations at 61-70⚬N were compared with predictions from the growth model. Published field data from one Spanish, 15 British and four Danish populations at 44-58⚬N were included in the analysis to increase the latitudinal range. 2. Among the Norwegian populations, the ratio between observed and predicted growth rates was not significantly different from 1.00 in eight rivers, but was significantly higher in eight, and was significantly lower in six. Observed growth was highest, relative to predicted growth, in the coldest rivers. In Spanish, British and Danish rivers, observed growth did not exceed predicted growth. 3. The ratio between observed and predicted annual growth rate decreased significantly with increasing annual mean temperature. Observed annual growth was higher than predicted growth only in rivers with an annual mean temperature lower than 5.1⚬C, and this indicates that some kind of thermal adaptation may occur in trout populations in the coldest rivers. 4. Regression analyses showed that besides the direct effects of temperature and body size predicted by the growth model, annual growth rates were significantly related to annual mean temperature, densities of juvenile salmonids, duration of twilight (average for May-August) and latitude. Adding these variables to the original model increased the explanatory power from 73.9 to 80.6%.