Bioenergetics and mercury dynamics in fish: a modelling perspective

The concentration of mercury in fish generally increases with age and size. Although a number of hypotheses have been invoked to explain this pattern, our understanding of the processes regulating the accumulation of mercury in fish is currently inadequate. In this study, we used a simple mass balance model to explore how the relationship between mercury concentration and fish age is affected by bioenergetics processes and prey contamination. We show that mercury concentration increases with fish age when older fish consume more contaminated prey or when metabolic costs associated with activity also increase with fish size. Our analyses further indicate that the relative importance of growth rate, activity costs, and consumption rates for mercury concentration can vary widely. We also show that changes in the energy density of fish and their prey with fish size could also affect the relationship between mercury concentration in fish and age. Application of this mass balance model indicates that bioenergetics models underestimate the activity costs of lake trout. A simple approach is presented to estimate activity costs of fish under field conditions.