Development and Evaluation of a Bioenergetics Model for Bull Trout

Abstract

We conducted laboratory experiments to parameterize a bioenergetics model for wild Bull Trout Salvelinus confluentus, estimating the effects of body mass (12–1,117 g) and temperature (3–20°C) on maximum consumption (C _max) and standard metabolic rates. The temperature associated with the highest C _max was 16°C, and C _max showed the characteristic dome-shaped temperature-dependent response. Mass-dependent values of C _max (N = 28) at 16°C ranged from 0.03 to 0.13 g·g⁻¹·d⁻¹. The standard metabolic rates of fish (N = 110) ranged from 0.0005 to 0.003 g·O₂·g⁻¹·d⁻¹ and increased with increasing temperature but declined with increasing body mass. In two separate evaluation experiments, which were conducted at only one ration level (40% of estimated C _max), the model predicted final weights that were, on average, within 1.2 ± 2.5% (mean ± SD) of observed values for fish ranging from 119 to 573 g and within 3.5 ± 4.9% of values for 31–65 g fish. Model-predicted consumption was within 5.5 ± 10.9% of observed values for larger fish and within 12.4 ± 16.0% for smaller fish. Our model should be useful to those dealing with issues currently faced by Bull Trout, such as climate change or alterations in prey availability.

Received December 12, 2011; accepted August 5, 2012

ACKNOWLEDGMENTS

This paper is dedicated to the memory of our colleague and friend, James H. Petersen. Jim was a guiding force on this project, and it was a pleasure and a privilege to work under his tutelage. We thank Howard Schaller of the U.S. Fish and Wildlife Service for financial, scientific, and administrative support; Don Ratliff, Scott Lewis, Megan Hill, and personnel from Portland General Electric for their financial support and constant willingness to help in the field; Susan Gutenberger, Ken Lujan, and Mary Peters of the Lower Columbia Fish Health Center for their fish health screenings; the Eagle Creek (Estacada, Oregon), Spring Creek (Underwood, Washington), and Little White Salmon (Cook, Washington) National Fish Hatcheries, and the Eells Springs State Fish Hatchery (Shelton, Washington), for kindly providing us with prey fish; and Kyle Martens, Jason Ontjes, Brien Rose, and Joe Warren of the CRRL for field and laboratory assistance. Comments by Jason Romine, Bianca Streif, and two anonymous reviewers improved the manuscript. Partial funding for this project was provided by the Great Northern Landscape Conservation Cooperative under agreement 60181AN408. The Washington Cooperative Fish and Wildlife Research Unit is jointly sponsored by the U.S. Geological Survey, the University of Washington, Washington State University, the state of Washington Departments of Fish and Wildlife, Ecology, and Natural Resources, and the U.S. Fish and Wildlife Service. Mention of trade names does not imply endorsement by the U.S. Government.