Líffræðifélag Íslands - biologia.is
Líffræðiráðstefnan 2017

Erindi/veggspjald / Talk/poster E56

Effect of food abundance on territory size in stream salmonids: A review

Höfundar / Authors: Stefan Ó. Steingrímsson (1) James W.A. Grant (2), Laura K. Weir (3)

Starfsvettvangur / Affiliations: 1. Department of Aquaculture and Fish Biology, Hólar University College, Sauðárkrókur, Iceland, 2. Department of Biology, Concordia University, Montréal, Canada, 3. Department of Biology, Saint Mary’s University, Halifax, Canada

Kynnir / Presenter: Stefán Óli Steingrímsson

How the density of territorial animals responds to changes in food abundance depends on the flexibility of territory size. Stream salmonids are an ideal model system for investigating flexibility in territory size, because food abundance can be quantified in the field and manipulated in the laboratory. We conducted a meta-analysis to test whether territory size decreases with increasing food abundance, and to test among three competing predictions: with increasing food abundance, territory size will be (1) fixed – the slope of a regression of log territory size vs. log food abundance = 0; (2) flexible and decreasing, as if individuals are defending a fixed amount of food – a slope = -1; and (3) initially compressible, but with an asymptotic minimum size – a slope between 0 and -1. We used data from 16 studies that reported both food abundance and territory size of age 0+ salmonids; 10 were laboratory experiments, but six were observational field studies. Overall, territory size decreased with increasing food abundance; the weighted average correlation coefficient was -0.31. However, the estimated slope of the relationship between log territory size and log food abundance was only -0.23, significantly different from 0, but also shallower than -1. This suggests that attempts to increase the density of territorial salmonids by increasing food abundance and reducing territory size will be inefficient; a 20.4 fold increase in food would be required to double population density.