Field data and growth model for mussels Mytilus edulis in Danish waters

Growth rates of blue mussels, Mytilus edulis, in suspended net-bags were measured in field experiments conducted in Limfjorden and Great Belt, Denmark, for extended periods of time (22 69 days) with up to 8 intermediate data samplings during the period. The resulting time series of growth of different overlapping size-classes of M. edulis were analysed individually and after being assembled to cover the full range of sizes, as full time series in terms of weight specific growth rate (μ = (1/W) dW/dt,% day^-1) as a function of dry weight of soft parts (W, g). The results were compared to a simple bioenergetic growth model for mussels (μ = aW^b, a = 0.871 x C - 0.986, b = -0.34), and observed power-law relations of growth data were in good agreement with the model, which takes into account the prevailing average chlorophyll a (chl a) concentration (C, μ g chl a l^-1) at field sites. Thus, the b-values of data were close to the predicted -0.34 while the
a-value was in one case lower than estimated due to suboptimal conditions during part of the growth period. As a supplementary interpretation the growth data have been expressed in terms of the time to double the dry weight of soft parts for a given size of mussel and at a given experimental site.