PREDICTING BIOMASS OF ATLANTIC SALMON FROM MORPHOMETRIC LATERAL MEASUREMENTS

Previously biomass predictions have been derived from simple weight-le ngth relationships. This study measured a variety of truss and convent ional dimensions covering the lateral body profile of Atlantic salmon Salmo salar and, using regression analysis, developed a series of mult ifactor weight-lateral dimension relationships. Single-factor regressi on equations proved inadequate for predicting weight with percentage e rrors between real and estimated values ranging from -1.2 +/- 6.8% to 72.5 +/- 225.6%. Fifty-two multifactor regression equations were gener ated that predicted accurately the weight of individual fish to within +/-2% using combinations of conventional and truss measurements. Regr ession coefficients were found to be significantly different (P<0.05) between Scottish and Norwegian strains, indicating morphological diffe rences between the genetic groups. Norwegian fish were generally heavi er for a given length compared to Scottish strains. This suggests that morphologically different strains of S. salar would require individua l weight : lateral dimension relationships to be developed in order to predict biomass accurately to within commercially acceptable levels. (C) 1996 The Fisheries Society of the British Isles