Revisiting the restricted movement paradigm: the dispersal of Atlantic salmon fry from artificial redds

Abstract

The Restricted Movement Paradigm (RMP) asserts that stream fishes are sedentary, living much of their lives within a single reach. To test the RMP, we implanted eyed Atlantic salmon eggs (Salmo salar L.) into a total of 19 artificial redds, in seven salmon-free streams, in six years, and estimated summer fry dispersal through electrofishing surveys. As expected, most fry dispersed downstream, but an average of 35% moved upstream. Surprisingly, fry moved just as far upstream as downstream (medians = 403 and 404 m, respectively). Fry were larger at lower densities and farther from redd sites, consistent with density-dependent growth, and larger upstream than downstream, possibly indicating that larger fry were better able to move upstream against the current. Dispersal distances were normally distributed around all but two of 19 redds, and half of the downstream dispersal curves were best described by unimodal distributions, consistent with a homogeneous movement strategy. Our data suggest that salmon fry were more mobile and move upstream more than previously thought, which should facilitate their stocking or reintroduction to new habitats.

Upstream and Downstream Dispersal Behavior of Hard‐ and Soft‐Released Juvenile Atlantic Salmon

“…Taken together, these results suggest that the soft-release tactic does affect the short-term dispersal and potentially the spatial distribution of hatchery-reared Atlantic Salmon in the wild. The observed stronger site fidelity-less dispersal away from release site-for acclimatized fish is in line with previous acclimatization studies in salmonids (Cresswell and Williams 1983;Kaya and Jeanes 1995;McCormick et al 1998;Jonssonn et al 1999;Eisenhauer et al 2021). Previous studies have found that wild European Grayling are less likely to disperse from release sites than are their hatchery-reared conspecifics (Turek et al 2010).…”

“…Along with rate of dispersal, other common measures of movement behavior are dispersal patterns and spatial distribution (Egglishaw and Shackley 1973, 1980; Beall et al. 1994; Crisp 1995; Teichert et al 2011; Foldvik et al 2012; Eisenhauer et al 2021). Analyses of dispersal and spatial distribution can involve simply measuring movement in a single dimension (upstream and downstream; Eisenhauer et al 2021).…”

Captive-breeding and catch-and-release’s effects on the reproductive success of Atlantic salmon (Salmo salar L.)

“…obs.). These observations have also been reported in Garant et al (2001) and strongly suggests that females might have constructed multiple redds since fry generally have low dispersal ability (< 1.5 km, Eisenhauer et al 2020).…”

High summer temperatures are associated with poorer performance of underyearling Atlantic salmon (Salmo salar) in upland streams

“…to move a mean distance of 403 m both upstream and downstream, with a maximum mean dispersal distance of 1.23 km upstream and 2.14 km downstream (Eisenhauer et al, 2021). In the present study we were unable to separate migration and mortality using the data available, but there was no evidence for sites further downstream having higher densities (Figure 1c), suggesting that any such effect was minimal.…”