Habitat effects on early post-settlement growth of intertidal clams,Venerupis philippinarum(A. Adams & Reeve, 1850)

Abstract

Understanding early growth is important for linking population dynamics with the ecological role played by bivalves in marine systems. Extensive literature exists for growth rates of juvenile and adults (>1 mm), but much less is known about growth rates during the period immediately following settlement in natural settings. In this study, growth rates from six cohorts of recently settled and metamorphosed (<300 µm) Manila clams (Venerupis philippinarum) are reported. Early post-settlement growth is compared over 2 years and from four intertidal sites in Baynes Sound, British Columbia, Canada, to assess how growth varies in response to local habitat (sediment chemistry and grain size) and conspecific abundance (Allee effects). Growth rates ranged from 2.8 to 5.3 µm d−1; instantaneous growth ranged from 0.005 to 0.007 d−1. Early post-settlement growth showed no density dependence relative to conspecific early recruit density or adult biomass. Average daily growth of early post-settlement clams was negatively correlated with inorganic carbon, organic carbon and nitrogen in the sediment, and growth tended to increase with increasing fraction of gravel. Early post-settlement growth rates observed here are less than those reported elsewhere for V. philippinarum, a discrepancy that may be explained by latitudinal differences and/or differences in settlement timing.