GROWTH-RATES IN OUTBREAK POPULATIONS OF THE CORALLIVOROUS GASTROPOD DRUPELLA-CORNUS (RODING 1798) AT NINGALOO REEF, WESTERN-AUSTRALIA

Mark and recapture experiments were used to estimate the size-at-age relationship of the coral-eating gastropod Drupella cornus at Ningaloo Reef, Western Australia. Animals 15 mm long increased in length by 5.2 mm in six months at a site in an early stage of an outbreak, but by only 3.8 mm at a site within an established outbreak. Snails larger than 35 mm grew very little. Based on observed growth rates fitted to a Richards function growth equation, snails 28 mm long judged to be reproductively mature would be 2.5 to 3.5 years old, suggesting that local outbreaks represent no more than one or two generations of recruits. Indirect evidence indicates that growth is more rapid in the earlier than in later stages of outbreaking populations. The growth and timing of life-history transitions of D. cornus are not unusual among other muricid species.