Effets de la densité sur la croissance du bivalve Macoma balthica (L.) en zone intertidale

Abstract

Experimental and descriptive field studies were conducted on an intertidal population of the infaunal bivalve Macoma balthica (L.) in the St Lawrence estuary in order to investigate the effect of density on growth and recruitment. The study of spatial variations in density and shell growth on the tidal flat was based on a stratified random sampling using three tidal level zones as strata. Mean population density over the whole area was 1302 · m −2; densities were higher and more variable near mean water level. Shell-growth rate and mean shell length of each generation increased with immersion time. There was a strong density effect on shell growth which increased with tidal level. The population was food limited in the upper two-thirds of the flat. The effect of density on shell growth was confirmed by a completely randomized block design experiment in the upper intertidal level. There was also a density effect on total tissue dry weight and on gonad size, but there was no significant effect of adult density on recruitment.