A Molluscan Population with an Unusual Size Frequency-Distribution

Abstract

THE toheroa (Amphidesma ventricosum, Gray) is a lamellibranch mollusc which occurs buried to a depth of several inches in sandy beaches mainly on the west coast of the North Island of New Zealand. This species, which is a prized table-delicacy, has generally been believed to confine itself to a strip of beach between low- and high-tide marks. However, abrupt fluctuations in population density which occur from time to time have cast some doubt upon the assumption that the intertidal beach zone is the only habitat of this mollusc.