Multiple central‐place territories in wild young‐of‐the‐year Atlantic salmonSalmo salar†

Abstract

Summary 1.The space use of central-place foragers, animals that forage from and return to a single central place such as a nest, burrow or sleeping site, is well documented. Limited data, however, exist for multiple central-place foragers that alternate among several central places. 2. The conventional view of stream-dwelling salmonids suggests that they conform to the centralplace territorial model (CPTM) by (i) attacking prey and intruders from one primary foraging station, and defending (ii) small (iii) exclusive areas that (iv) increase with body size. 3. Recent studies suggest greater variability in salmonid space-use than would be expected by the CPTM, but tend to focus on the time allocated towards different activities rather than their distribution in space, especially for young-of-the-year (YOY) fish that are hard to tag and monitor in the wild. 4. In this study, the validity of CPTM was tested by mapping the daily space use of 50 YOY Atlantic salmon in a natural stream via repeated observations of tagged fish in diverse habitats, and by comparing these to earlier estimates of territory use in YOY salmonids. 5. The 50 YOY Atlantic salmon were multiple central-place foragers. All fish visited more than one foraging station (median = 12·5 stations), visited most stations (68·5%) repeatedly, showed limited fidelity to a particular station and typically attacked prey only while holding a position at a station. 6. The multiple central-place territories of the 50 fish were large (mean = 0·932 m 2 ) compared to earlier territory size estimates (mean = 0·107 m 2 ) for salmonids of similar size and, surprisingly, did not increase with body size. Focal fish attacked intruders from similar distances as reported earlier for much smaller territories, suggesting that large territories are less exclusively defended at any given time. 7. Overall, this study provides a new view on foraging and territoriality in stream salmonids, and on the small but diverse literature on multiple central-place foragers. Further studies, however, are needed to clarify the evolutionary benefits and population consequences of multiple central-place space-use in mobile animals.

The spatial scale of competition from recruits on an older cohort in Atlantic salmon

“…In many of these species, juveniles originating from several potentially competing cohorts live in sympatry. These fish usually defend a single spatial location against intruders at any given time, although individuals may move among different patches of space through time (Steingrimsson and Grant 2008). Behavioural observations suggest strong body size effects on the ability of salmon parr to control access to space (Cutts et al 1999).…”

Modelling brown trout spatial requirements through physical habitat simulations

“…Such variations may result from differences in habitat selection patterns or metabolic requirements between species. In addition, salmonids can behave as single or multiple central-place foragers, and the proportion of individuals switching from one to another pattern of space use varies across species and populations (Steingrímsson and Grant, 2008). Furthermore, we also detected intraspecific differences, since trout in our study area had significantly larger territories than equally-sized individuals of the population described by Elliott (1990).…”

Quantification and comparison of individual space-use strategies in foraging drift-feeding fish using fine-scale, multidimensional movement analysis

“…Trout with a higher horizontal UD50 were using two, or more, clearly defined positions, which corresponds with what has been described as multiple central-place territories by Steingrimsson and Grant (2008). This space-use strategy was displayed by a majority of the trout monitored (66%), and could reflect social status, as the use of multiple positions has been associated with subordinate social status in other salmonids (Nakano 1995).…”