Variability in performance in wild Atlantic salmon, Salmo salar L., fry from a single redd

Abstract

Dispersal and growth were studied in Atlantic salmon, Salmo salar L., fry from a natural isolated redd. The distribution of fry leaving the redd was strongly peaked, 80% being caught within a 2‐week period. Early in the dispersal period, all fry leaving the redd had remnants of yolk sac and had not fed; by half way through the dispersal period, no fry had any visible yolk, but 35% still had empty stomachs. Fry leaving the redd during the first half of the dispersal period tended to settle in different first feeding sites than those dispersing later. Predation on fry by larger salmonids was frequent, especially during dispersal. Coefficients of variation for length, weight and condition factor increased significantly over the study period and for individually recognised fry, growth rates varied markedly. Thus, individual salmon fry differ in physical status on emergence from the redd and these differences are amplified during the first few weeks after emergence.

Influence of energetic status on ontogenetic niche shifts: emergence from the redd is linked to metabolic rate in brown trout

“…However, this relationship is a consequence of the time spent under gravel, with early emerging fry having more un-metabolized yolk than later emerging conspecifics. This agrees with previous hypotheses for Atlantic salmon and brown trout (Garcia De Leániz et al 2000;Skoglund and Barlaup 2006). Our results also suggest that emergence from gravel is not triggered by energetic constraint: firstly, because all emerging fry had some yolk remaining at the time of emergence, and secondly, relative energetic content decreased through the emergence period.…”

Multigenerational hybridisation and its consequences for maternal effects in Atlantic salmon

“…Some authors use the percentage of body mass to total mass as an index of development to predict first feeding at 97% body wet mass (Thorpe et al, 1984). Yet, fry in the wild might start feeding in the gravel (GustafsonMarjanen and Dowse, 1983) and early emerging fry have externally visible yolks (Garcia de Leaniz et al, 2000). In our study, externally visible yolks were observed on some individuals upon dissection of fry.…”

Local-scale density-dependent survival of mobile organisms in continuous habitats: an experimental test using Atlantic salmon

“…During this period, the juveniles have a narrow range of microhabitats in which they can obtain positive growth, and thus only a small proportion of the total river habitat can be exploited (Nislow et al 2000). Furthermore, there appears to be a strong limitation to successful dispersal during this initial stage (Beall et al 1994;De Leaniz et al 2000;Webb et al 2001;present study). A limitation to dispersal may be caused by energetic costs and the lack of feeding opportunities during dispersal, which may eventually lead to starvation.…”

“…These studies highlight the importance of density dependence, but give little detail about its potential spatial scale. If dispersal abilities are limited during the early stages when density dependence occurs (e.g., Beall et al 1994;De Leaniz et al 2000;Webb et al 2001), and breeding within a population occurs on spatially separated patches of a suitable breeding habitat, one might hypothesise that the population-level stockrecruitment curve is a result of several more or less independent density-dependent relationships, each one being manifested within a spatial scale limited in extent by the maximum dispersal distance from patches of breeding habitat.…”