Evaluation of Bioenergetics Models for Predicting Great Blue Heron Consumption of Rainbow Trout at Hatcheries

Abstract

Abstract We predicted consumption of rainbow trout Oncorhynchus mykiss by great blue herons Ardea herodias by combining a population estimate of predators with bioenergetics models of (1) existence metabolism (ME), (2) existence metabolism plus reproductive costs (MEBreeding), and (3) field metabolic rate (FM) for individual great blue herons. We then compared predicted consumption to directly estimated consumption by a free-ranging population of great blue herons foraging at a fish hatchery. Although the FM model predicted annual population consumption rates similar to observed annual consumption, model predictions differed significantly from directly estimated consumption for 6 months. Monthly consumption predicted by the existence metabolism models agreed with directly estimated consumption from October to June. During the breeding season (May–July), directly estimated consumption was higher than predicted by the ME model for nonbreeders but was lower than predicted by the MEBreeding model. This result...