Individuals travelling through landscapes may use the presence of conspecifics to evaluate habitat quality. Juvenile Atlantic salmon (Salmo salar L., 1758) are usually territorial and exhibit some degree of density-dependent regulation in wild populations. They are also vulnerable to heat stress and may need to locate a thermal refuge to offset metabolic costs above certain temperature thresholds. During July 2010, a heat wave resulted in water temperatures in the Miramichi River system exceeding 30 °C. During this period, salmon parr were observed aggregating in cold-water refugia at densities several orders of magnitude greater than usual. We tested whether groups of wild-caught salmon parr held at high densities (160 parr/m2) would have an attractant effect on free-swimming parr at three sites differing in temperature between 16.5 and 24 °C. Although neither temperature nor site influenced the number of parr that we observed, there were significantly more parr in close proximity (<1 m) to the artificial aggregations than to the controls. These results suggest that social cues from high-density aggregations of conspecifics during extreme temperature events may advertise the location of thermal refugia to others. Understanding how heat-stressed salmon locate refugia may prove valuable to ongoing conservation efforts given the likelihood of increasingly frequent and extreme high-temperature events.

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Keywords Aggregations, Atlantic salmon, Heat stress, Information use, Parr, Salmo salar, Territoriality, Thermal refuge/refugia
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Journal Canadian Journal of Zoology
Elvidge, C.K. (Chris K.), Cooke, E.L.L., Cunjak, R.A., & Cooke, S.J. (2017). Social cues may advertise habitat quality to refuge-seeking conspecifics. Canadian Journal of Zoology, 95(1), 1–5. doi:10.1139/cjz-2016-0144