Development and evaluation of a combined bioenergetics and organic chemical mass-balance bioaccumulation model for fish.

This study describes the development and evaluation of a new bioenergetically-balanced bioaccumulation (3B) model for organic chemicals in fish. The 3B model is developed from a large database of routine metabolic (oxygen consumption) rates comprising a range of species, body mass and temperature. The chemical uptake and elimination rates of the 3B model are compared against those from three existing bioaccumulation models. A time-variant version of the 3B model is evaluated against measured concentrations of five polychlorinated biphenyls in different size fish depurated over the course of a year including a 22 oC change in ambient temperature. The "generic" species 3B model predicts fish concentrations to within a factor of 3 of the measured data for the majority of observations (n = 438) and outperforms a previously published "species-specific" bioenergetics model derived from model calibration. Bioenergetics aspects of the 3B model are further evaluated by comparing predicted feeding rates and growth rates to measured rates obtained from diverse laboratory conditions (n = 572). While bioenergetics performance is acceptable, the 3B model generally performs better when ingestion rates are calculated from growth rates rather than the opposite. For field applications, parameterization of the activity multiplier remains a key uncertainty underlying the bioenergetics calculations.