Dispersion of Atlantic salmon (Salmo salar) fry from competing families as revealed by DNA profiling

Abstract

Minisatellite-based DNA profiling was used to investigate the dispersion of synchronously spawned families of Atlantic salmon (Salmo salar L.) fry from artificial nests in a natural stream. By the end of the summer, i.e., 17 weeks after hatching, detected dispersion was mainly downstream and less than 1 km. Within this distance, three families that had been stocked together showed different patterns of dispersion, with the relative abundance of each family changing systematically with distance downstream from the nest, but with no monopolization of any area or habitat type by any one family. The length of fry also changed systematically with distance downstream, with the patterns of change depending on family. For each family, fry were larger closer to the nest. Changes in habitat type had a common effect on the density and length of fry from all the families.

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.…”

Regional variability in Atlantic salmon (Salmo salar) riverscapes: a simple landscape ecology model explaining the large variability in size of salmon runs across Gaspé watersheds, Canada

“…We then tested whether salmon preferentially choose quality spawning segments within relatively close proximity (for adult, fall spawning displacements) upstream of a BC. Furthermore, the movement of young salmon juveniles is predominantly in the downstream direction (Johnston 1997;Webb et al 2001;Bujold et al 2004), and BC segments are characterised as being rich in both bouldersized sediment, deep holding pools and cooler, shaded waters. Hawkins & Smith 1986).…”

Spatial distribution of Atlantic salmon (Salmo salar) breeders: among- and within-river variation and predicted consequences for offspring habitat availability

“…Although some upstream dispersal from nests may occur, this is expected to be limited both with respect to frequency and distance during the initial stage (García De Leániz et al 2000), which is when competition and local density-dependent mortality is intense (Einum and Nislow 2005) and hence when the issue of habitat availability may be most important. Downstream dispersal has been observed to occur up to 1 km downstream of nests throughout the first summer (Crisp 1995;Webb et al 2001), but this appears to be rare, and utilization can therefore be expected to be low for the majority of habitat within such a long distance. Furthermore, long-distance dispersal is likely even less common during the first few weeks after emergence from nests, and Einum and Nislow (2005) reported a median absolute dispersal distance of 41 m (range 0-884 m) 1 month after emergence.…”

“…Thus, any aggregation of breeding will result in pronounced spatial heterogeneity in the distribution of eggs within populations. Because of limited dispersal of juveniles from nests (Beall et al 1994;Webb et al 2001;Einum and Nislow 2005), such heterogeneity in the distribution of eggs can influence the subsequent spatial distribution and growth of juveniles during their first summer, both over small spatial scales (tens of metres) in experimental situations (Einum et al 2008b) as well as over larger spatial scales (hundreds of metres) in natural populations (Foldvik et al 2010). Furthermore, the restricted mobility of offspring following emergence from nests (median dispersal distance < 100 m; Einum and Nislow 2005) can cause intense competition and local density-dependent mortality (Einum and Nislow 2005;Einum et al 2008b).…”