Aspects of the population dynamics of Chione stutchburyi in Ohiwa Harbour Bay of Plenty, New Zealand

Abstract

Current research has highlighted the importance of an understanding of small scale variation in population processes, in the interpretation of either observational or experimental data. The fine scale spatial and temporal variation of a Chione (Austrovenus) stutchburyi (Finlay 1927), (Veneridae: Bivalvia) population within Ohiwa Harbour, Bay of Plenty, New Zealand, is studied using descriptive and correlative techniques, for three years (May 1978 to December 1981) to identify factors influencing the demographic mechanisms of survival, recruitment and growth. This work follows pilot studies to determine the scale of local variation. The importance of fine-scale spatial variation is discussed and the temporal stability of small-scale population density mosaics analysed. Data shows that the chione stutchburyi population is spatially variable on a fine scale, but that these density contours are time-stable. The results of field experiments show that total density within cage structures is maintained at an equilibrium density that is site-specific on a local scale. The mechanism that maintains these density levels, under an apparently low level of predation on adult size classes, appears to be intraspecific competition, overlaid by spatially and temporally variable recruitment. The effects of artifacts induced by cage structures on the soft-sediment environment for a sheltered tidal harbour are examined.