Allometry of territory size and metabolic rate as predictors of self‐thinning in young‐of‐the‐year Atlantic salmon

• Published in: Journal of Animal Ecology
• Main Authors: Steingrímsson, Stefán Ó., Grant, James W. A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1999
• Subjects: Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1046/j.1365-2656.1999.00261.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-2656.1999.00261.x; https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2656.1999.00261.x; https://onlinelibrary.wiley.com/doi/full-xml/10.1046/j.1365-2656.1999.00261.x; https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2656.1999.00261.x

1. Self‐thinning is a progressive decline in population density caused by competitively induced losses in a cohort of growing individuals and can be depicted as: log 10 (density) = c − β log 10 (body mass). 2. In mobile animals, two mechanisms for self‐thinning have been proposed: (i) the space hypothesis predicts that maximum population density for a given body size is the inverse of territory size, and hence, the self‐thinning slope is the negative of the slope of the allometric territory‐size relationship; (ii) the energetic equivalence hypothesis predicts that the self‐thinning slope is the negative of the slope of the allometric metabolic rate relationship, assuming a constant supply of energy for the cohort. 3. Both hypotheses were tested by monitoring body size, population density, food availability and habitat for young‐of‐the‐year Atlantic salmon ( Salmo salar ) in Catamaran Brook, New Brunswick. The results were consistent with the predictions of the space hypothesis. Observed densities did not exceed the maximum densities predicted and the observed self‐thinning slope of −1·16 was not significantly different from the slope of −1·12, predicted by the allometry of territory size for the population under study. 4. The observed self‐thinning slope was significantly steeper than −0·87, predicted by the allometry of metabolic rate, perhaps because of a gradual decline in food abundance over the study period. The decline in density was more rapid in very shallow sites and may have been partly caused by a seasonal change in water depth and an ontogenetic habitat shift rather than solely by competition for food or space. 5. The allometry of territory size may be a useful predictor of self‐thinning in populations of mobile animals competing for food and space.