Settlement and growth of the intertidal gastropod, Melarhaphe neritoides, on the south coast of Ireland

Abstract

Settlement and growth of Melarhaphe neritoides (L. ) were studied on two rocky shores, at Carnsore Point, County Wexford and Tragumna, County Cork, on the south coast of Ireland during the years 1977–1978 and 1983–1991 respectively. Settlement occurred in each year but varied in timing and density, with maxima of 30,000 m-2 at Tragumna and 3,800 m-2 at Carnsore Point. Recently settled individuals occurred in pools in the Verrucaria zone and on open rock below this level. Growth of the 0+ and 1+ cohorts was determined by analysis of length frequency distributions. Growth of older snails was estimated by measuring growth increments in marked animals. Recruits grew to less than 2 mm in shell height in their first year. Larger snails (>2 mm shell height) grew 0. 2–0. 3 mm shell height per year. It is estimated that M. neritoides takes over five years to reach a shell height of 3 mm at Tragumna.