Using modified length-weight relationships to assess the condition of fish

This paper develops a model to replace classical fish models used to assess weight and condition. Results from two classical models (M = KL3 and M = a L(b)) were compared to results from the proposed model (M = (BLH)-H-2) to f ind which one could be most accurately applied over the widest range of gen etic, morphological and physiological states. A large database of physical measurements was analyzed. The newly proposed model decreased the variabili ty in calculating weight by between 38 and 44% as compared to the conventio nal fisheries model M = KL3 and was consistently more accurate than M= aL(b ). Condition factor K of the two salmon species studied increased with fish weight, while the B factor was generally invariant. With regards to the sa lmonids, the B factor indicates a type of bodily streamlining, important fo r swimming functions. A low B factor indicates a fish has less cross sectio nal area per unit length than a high B value fish has. As well, the B facto r can be used to calculate girth. The new model can, therefore, be used to more accurately predict weight and physical state than other conventional m odels can. (C) 1999 Elsevier Science B.V. All rights reserved.