Seasonal variation in body weight of the bivalves Macoma balthica, Scrobicularia plana, Mya arenaria and Cerastoderman edule in the Dutch Wadden sea

Abstract

The paper deals with the seasonal and annual variations in the weight of the soft parts of four bivalve species, Macoma balthica, Scrobicularia plana, Mya arenaria and Cerastoderma edule from tidal flats of the Dutch Wadden Sea. The paper reviews methodology and points to error sources. The variation in ash-free dry weight between individuals of the same size collected at the same time and place could be attributed to age, parasitic infestation, gametogenesis, burying depth and siphon size. The allometric relations between weight of soft parts and size are given in equations, averaged per month. The body weight of all four bivalve species peaked in May and June at a level approximately twice the lowest value, which occurred in November to March. The extent of this seasonal fluctuation varied, however, from year to year. The presence of gametes explained a part of the peak weight in summer. Winter losses of body weight were less at low temperatures, due to reduced energy expenditure when the animals are inactive. No large differences were found between the seasonal changes in body weight in the Wadden Sea and elsewhere in the temperate zone.