Estimating food consumption rates of fish using a mercury mass balance model

Abstract

We present a simple method for estimating food consumption rates of fish in the field based on a mercury (Hg) mass balance model. This method requires the determination of fish age, size, and growth and Hg concentration in fish and their food. The model was validated using data obtained from a previously published laboratory experiment. A field test of the model showed that food consumption rates determined with the Hg mass balance model differed from independent estimates obtained with the 137Cs method by only 0.6-16.1%. The model was applied to fish from various lakes in Quebec and Ontario. Food consumption rates estimated with the Hg mass balance model varied significantly both among species and among populations. Furthermore, female fish tended to eat 30-40% more food than males, probably to meet the larger energy requirement associated with egg production. A sensitivity analysis indicated that the Hg mass balance model was mostly responsive to variables that can be easily measured in the field, such as fish size and Hg concentration in fish and their food. By providing a low-effort approach to quantifying food consumption rates of fish in the field, this method may help to refine our understanding of the environmental factors that influence the quantity of food consumed by fish.

Mercury Accumulation, and the Mercury-PCB-Sex Interaction, in Lake Whitefish (Coregonus clupeaformis)

“…To the best of our knowledge, our study was the first to assess the ratio of MeHg concentration to Hg concentration in lake whitefish. Typically, MeHg is the predominant form of mercury in fish [24,32]. However, only 16% of the Hg found in fillets of white perch (Morone americana) from the Hackensack River (NJ, USA) was MeHg, with the remainder of the Hg being inorganic mercury [33].…”

“…Typically, MeHg is the predominant form found in fish [32], but inorganic mercury can make a substantial contribution to Hg in some cases [33]. When modeling Hg accumulation in fish, all of the Hg found in the fish is often assumed to be MeHg [24].…”

Sex differences in contaminant concentrations of fish: a synthesis

“…The use of Hg mass balance models to estimate food consumption by fish has rapidly increased since 2000 [15, 16, 89, 90]. The Hg elimination submodel used in these Hg mass balance models was based on a regression model developed by Trudel and Rasmussen [41].…”

Seasonal shift in the effects of predators on juvenile Atlantic salmon (Salmo salar) energetics

“…The model, as adapted for stable isotopes and non-reproductive fish, is described in detail elsewhere (Kennedy et al 2004, Trudel et al 2000). Briefly, as fish accumulate methylmercury largely from the prey they consume, total prey consumption ( C , g•g −1 •d −1 ) can be estimated from initial methylmercury body burden ( B t , ng), the final methylmercury body burden ( B t+d where d is the number of days in the interval), the methylmercury concentrations in prey ( F , ng•g −1 ), and literature estimates for assimilation efficiency ( a , proportion) and elimination rate ( E , proportion).…”

“…This has long been technically challenging for field studies due to the practical difficulty in measuring time-integrated consumption rates of individual fish over days and weeks. We addressed this challenge by estimating prey consumption using a mass-balance model of methylmercury accumulation, an approach that yields robust, time-integrated individual consumption estimates over periods of weeks to months (Trudel et al 2000, Ward et al 2010a). This approach also allowed us to separate the effects of predators during the early critical period (ca.…”