Latitudinal variation in growth of young brown trout Salmo trutta

Abstract

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 eects of dierences in ambient temperatures and ®sh 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 ®eld 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 signi®cantly dierent from 1Á00 in eight rivers, but was signi®-cantly higher in eight, and was signi®cantly 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 signi®-cantly with increasing annual mean temperature. Observed annual growth was higher than predicted growth only in rivers with an annual mean temperature lower than 5Á1 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 eects of temperature and body size predicted by the growth model, annual growth rates were signi®cantly 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 73Á9 to 80Á6%.

The influence of hydroelectric power generation on the body composition of juvenile Atlantic salmon

“…Models for energy allocation in teleost fish use water temperature as a key factor, with both respiration and growth increasing with increasing water temperatures (e.g. Elliott, 1976;Elliott et al, 1995;Jensen et al, 2000;Jensen, 2003;Bacon et al, 2005). The traditional view is that when water temperatures drop below about 4-78C, investment into new tissues appears to stop for young salmonids (Elliott, 1976(Elliott, , 1991Elliott et al, 1995).…”

Latitudinal Variation in Sexual Size Dimorphism of Sea-Run Masu Salmon, Oncorhynchus Masou

“…Improved growth opportunities in fresh water lead to an increase in the incidence of male parr maturing in salmonids (e.g., Thorpe 1986). The deteriorated growth conditions in the fresh water at higher latitudes might therefore reduce the odds of parr maturation in the north (see Jensen et al 2000). In addition, many previous studies suggested that male parr exceeding a genetically determined threshold size go on to mature, and smaller male parr proceed to the ocean phase (e.g., Fleming 1996).…”

Effect of incubation temperature on growth performance in Atlantic salmon

“…Field studies on teleost fishes have revealed some evidence for the countergradient hypothesis, in particular, in studies on salmonids (Jensen et al 2000, Finstad et al 2004, Nicola & Almodóvar 2004. On the other hand, recent experimental studies have not supported either of the first 2 hypotheses , Jonsson et al 2001, Larsson et al 2005, but leave the third possibility open.…”