Prior residency advantage for Atlantic salmon in the wild: effects of habitat quality

Abstract

Prior residency advantages have been explained by an asymmetry between the ‘owner’ and the ‘intruder’ in fighting ability (resource-holding potential) or motivation (value asymmetry (VA)). Here, we tested for the extent of prior residence effects in individually tagged Atlantic salmon juveniles being released in two bouts (4 days apart) during spring along a natural stream, and recaptured 3 months later. A prior residency advantage was detected both in terms of body growth, energy density and male gonad size. As we controlled for effects of initial body size, which correlates with dominance, these findings are in accordance with the VA hypothesis. The growth advantage of first arrivals also increased with local shelter abundance in the stream, which can be expected if a higher resource value of the habitat results in a higher defence motivation. We also found a prior residence effect on spatial distribution, with the second arrivals within each release site being recaptured further downstream. No effect on apparent survival rates was found. The observed reduced growth and energy density may have fitness consequences for the second arrivals, both in terms of lower winter survival rates and later age at maturity. For mature male parr, both decreased body and gonad growth may give an additional disadvantage through reduced fertilization rates during breeding. These costs may help to explain the tendency for stationary behaviour of stream salmonids, as the potential benefits of moving into less crowded areas would be reduced by the risk of becoming an intruder. Prior residence effects may therefore have influenced the evolution of movement behaviour in these organisms.

Natal movement in juvenile Atlantic salmon: a body size‐dependent strategy?

“…Furthermore, downstream movement would not be expected to be limited even in the absence of movement abilities since the fish could move passively with the water flow. An alternative explanation could be that individuals that move have to compete with individuals already present when settling in a new location and that the latter ones would have the advantage of prior residence (Kvingedal and Einum 2011). However, given the typical patchy distribution of Atlantic salmon spawners and the resulting patchiness of juveniles during the first summer , it seems reasonable to assume that in many cases movers should manage to locate vacant positions.…”

Farmed Atlantic salmon Salmo salar L. parr may reduce early survival of wild fish

“…An important factor in the odds to establish and hold a territory is the timing of emergence, as early emerging alevins may have a competitive advantage owing to the prior residency effect (Hodge et al , ; Cutts et al , ; Kvingedal & Einum, ; Skoglund et al , ). In this study, hatching and emergence of farmed and wild S .…”

“…The low numbers of parr remaining in each of the large stream channels at termination of the experiment (0⋅2-0⋅8 parr m −2 , compared with 4⋅0-33⋅0 parr m −2 in the confined stream channels) may indicate that the habitat conditions were unsatisfactory, i.e. due to little shelter, which is strongly correlated with carrying capacity (Finstad et al, 2009) An important factor in the odds to establish and hold a territory is the timing of emergence, as early emerging alevins may have a competitive advantage owing to the prior residency effect (Hodge et al, 1996;Cutts et al, 1999;Kvingedal & Einum, 2011;Skoglund et al, 2012). In this study, hatching and emergence of farmed and wild S. salar offspring were intentionally synchronized by manipulating incubation temperature, to exclude prior residency effects.…”

Territorial resource valuation deviates from habitat quality in an ecologically trapped, long-distance migratory bird

“…Interestingly, we controlled for the impact of prior territorial ownership on fight intensity (e.g., Kokko et al 2006;Kvingedal and Einum 2011) because all males were tested at a comparable stage of their breeding cycle (i.e., prelaying courtship period before the egg-laying stage), but at different times over the course of the season depending on their arrival and pair formation date. With this experimental setup, we can be sure, unlike previous studies in migratory birds (e.g.…”