Multivariate experiments are used to study the effects of body size, food concentration,
and season on the oxygen consumption, ammonia excretion, food assimilation efficiency
and filtration rate of Mytilus edulis adults. Food concentrations and season affect both the
intercept and the slope of the allometric equation describing oxygen uptake as a function
of body size. Multiple regression and response surface techniques are used to describe and
illustrate the complex relationship between metabolic rate, ration, season and the body
size of M. edulis. Filtration rate has a relatively low weight exponent Q> = 038) and the
intercept for the allometric equation is not significantly affected by food concentration,
season or acclimation temperatures between 5 and 20 °C. Food assimilation efficiency
declines exponentially with increasing food concentration and is dependent on body size
at high food levels. The rate of ammonia excretion shows a similar seasonal cycle to that
of oxygen consumption. They are both minimal in the autumn/winter and reach a
maximum in the spring /summer