The ecology of two sandy beaches in south west India. III. Observations on the population of Donax incarnatus and D. spiculum

The biology of two species of Donax, D. incarnatus Gmelin and D. spiculum Reeve on two beaches in south west India is described. Two year groups of D. incarnatus were present on both beaches, from settlements during the monsoon period in 1967 and 1968. At Shertallai, both groups were studied through the year, and data on growth, mortality and production are presented. At Cochin, the rate of growth was slower and the maximum size attained smaller, but mortality during the early monsoon precluded study of D. incarnatus through a full year. D. spiculum occurred at Cochin mainly during the pre-monsoon period, and at Shertallai during the post-monsoon. The species has a shorter life-span than D. incarnatus, but its irregular occurrence did not allow detailed production estimates.