Estimation of body condition in harbour porpoises, Phocoena phocoena

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Abstract
I examined the body condition of 220 harbour porpoises (Phocoena phocoena) killed incidentally in commercial fishing operations in the Bay of Fundy between July and September, 1985–1988. Condition was assessed using a direct measure (blubber mass) and two indirect measures (blubber thickness and girth). To compare condition among porpoises of different sizes, each measure was regressed against an appropriate measure of body size, and the residuals of these regressions were used as indices of condition. Mean residuals of blubber mass varied significantly among both reproductive classes and sampling years. Calves and nonlactating mature females had greater mean residual values for blubber mass than immature porpoises and mature males; lactating females possessed intermediate levels. Porpoises sampled in 1987 had greater mean residual blubber mass than porpoises sampled in other years. Although the residuals of girth and blubber thickness demonstrated similar trends to those of blubber mass, they were poorly correlated with the residuals of blubber mass and are not robust indices of condition in harbour porpoises.