In a recent article, a new factor has been proposed to assess condition in
fish (Jones et al. 1999). It is based not only on body mass and length, but
also on body height. The new factor, B (= M/(L-2 x H); M, L and H = body m
ass, length and height, respectively), was tested against the traditional f
actor of Fulton, (K = M/L-3) using data sets for two salmonid species, and
it was found to be a better predictor of body mass from body dimensions. B
assumes that body thickness is better correlated with length than height. T
o test this, we compared K and B, as well as K' (= M/L-b; b derived from re
gression of Log[M] against Log[L]) and B '(= M/(L x H-2)), using data on mi
lkfish, Chanos chanos. The factor B' consistently gave the best results, an
d in larger fish K' was found to be a better predictor of body mass than B.
Regression analysis of body mass and height on length showed that body thi
ckness varies isometrically with height but allometrically with length, exp
laining why B' is better than B.