Comparison of Encounter Model Predictions with Observed Size-Selectivity by Stream Trout
- 1 March 1987
- journal article
- research article
- Published by University of Chicago Press in Journal of the North American Benthological Society
- Vol. 6 (1) , 56-64
- https://doi.org/10.2307/1467524
Abstract
Observed size-selective predation on the amphipod Gammarus pseudolimnaeus by trout was compared with encounter model predictions based on drift and benthic samples over seven months. The generalized encounter model used predicts that the proportion (Fi) of prey size i in the diet will be: Fi=Liα· Ni/Σ Liα· Ni where Li = size (length) of prey group i, Ni = density of prey group i in the environment, and α = an exponent related to the reactive field searched. In five of seven months, the encounter model reasonably predicted prey-sizes consumed (percent similarities > 85%). For four of these months, benthic size-distributions resulted in the best predictions; the drift size-distribution resulted in best fit in August. Observed size-selectivity in May and July was greater than predicted with commonly used values of α, showing that factors other than encounter were also involved in prey size-selectivity.Keywords
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