SIMULATION OF ALTERNATIVE ASSUMPTIONS OF FISH OTOLITH-SOMATIC GROWTH WITH A BIOENERGETICS MODEL

Three different assumptions of the otolith-somatic growth relation wer e simulated using an individual-based bioenergetics model. The LINEAR model assumed that otolith growth was directly related to somatic grow th; the TEMP-WT assumed that otolith growth was a function of ambient temperature and the weight of the fish; and the O2CON model assumed th at otolith growth was a function of oxygen consumption. Although the L INEAR model resulted in an otolith radius-total length relation most o ften observed in nature (linear), otolith growth in the model ceased a t temperatures and food rations that curtailed somatic growth, which c ontradicts some other studies. Model otolith growth continued at tempe ratures and ration levels that curtailed somatic growth in the TEMP-WT and O2CON model, however the resulting otolith radius-total length re lation 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 fis h had larger otoliths when growth was limited by temperature. Differen t geometries between the fish body and otolith resulted in different g rowth 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. (C) 1997 Elsevier Scienc e B.V.