Modeling the oxygen consumption rates in pacific salmon and steelhead: An assessment of current models and practices

Bioenergetic models of fish have been used to study a large number of processes. Like most models, bioenergetic models require the estimation of numerous parameters. As a consequence, they have often relied on parameters borrowed from other species or values extrapolated from other life stages or size-classes. The magnitude of the biases associated with these practices remains largely unknown. The objective of this study was to determine whether or not metabolic rates could be extrapolated between closely related species and life stages. We focused on Pacific salmon Oncorhynchus spp. and steelhead O. mykiss, as the metabolic rates of these species have been well documented. Our analyses showed that models derived from closely related species did not accurately predict the metabolic rates of salmon, indicating that the practice of "species borrowing" should be avoided in assessing fish metabolic rates. Our work also showed that allometric equations of metabolic rates were not stable when measured over small size ranges and that biases could be introduced when these models are extrapolated to smaller or larger fish. In addition, we found that, except for steelhead, published models of Pacific salmon metabolic rates were inaccurate. Mean bias ranged from close to 0% to over 200% depending on size and water temperature, with about two-thirds of the bias values exceeding 20%. These biases could have large impacts on bioenergetic model predictions. Increased funding and scientific recognition of the need for additional basic research will be necessary to build more accurate bioenergetic models for Pacific salmon, especially models applied to the ocean phase of the life cycle.