Distribution, growth and seasonal changes in biochemical composition for the bivalve Donax vittatus (da Costa) from Kames Bay, Millport

Abstract

The bivalve Donax vittatus (da Costa) occurs in Kames Bay, Millport, Scotland,only intermittantly. Successful settlements may occur with a frequency of no more than two in twenty years. There was one such settlement in the summer of 1962. The distribution in 1967 of survivors from this settlement was mainly just below L.W.S.T. Shell ring measurements indicated that the maximum mean size was reached in 5–6 years. Seasonal changes in body weight and biochemical composition are associated with the processes of reproduction, growth, and storage and utilization of reserves. The main period of increase in reserves and of gametogenesis corresponded with the spring peak of diatom abundance. The autumn peak of phytoplankton abundance is apparently less well utilized, although there is some increase in carbohydrate reserves. Spawning, which occurs in the early summer, produces a marked fall in the mean body weight, and a slower fall during the winter months is the result of elimination of reserves to meet the metabolic demands of the animal when food is scarce.