Simulation of alternative assumptions of fish otolith–somatic growth with a bioenergetics model

Abstract

Three different assumptions of the otolith–somatic growth relation were simulated using an individual-based bioenergetics model. The LINEAR model assumed that otolith growth was directly related to somatic growth; the TEMP–WT assumed that otolith growth was a function of ambient temperature and the weight of the fish; and the O2CON model assumed that otolith growth was a function of oxygen consumption. Although the LINEAR model resulted in an otolith radius–total length relation most often observed in nature (linear), otolith growth in the model ceased at temperatures and food rations that curtailed somatic growth, which contradicts some other studies. Model otolith growth continued at temperatures and ration levels that curtailed somatic growth in the TEMP–WT and O2CON model, however the resulting otolith radius–total length relation from the O2CON model was not as similar to naturally occurring ones. In all three models slower growing fish had larger otoliths than did faster growing fish of the same size when somatic growth was food limited. However, in the TEMP–WT and O2CON models, faster growing fish had larger otoliths when growth was limited by temperature. Different geometries between the fish body and otolith resulted in different growth rates between the two structures in terms of length, despite the fact that their growth rates in terms of weight were identical. This implies that a comparison between somatic and otolith growth needs to consider and specify the dimensions involved.