ABSTRACT
Dhofar experiences unique oceanic conditions during the SW monsoon from June to September. The ubiquitous tropical echinoid Echinometra mathaei was sampled at 6-monthly intervals from March 1988 to September 1989. Body indices were investigated to determine the effects of the monsoon on reproduction, growth and resource allocation. The results indicate that spawning occurs immediately before or during the monsoon when sea temperatures, depressed by upwelling, appear too low for gonadal growth. Gonad and body wall indices increase between October and April, when water temperatures are above 18°C and when suspended food is abundant. Lantern indices show a reverse trend but they increase as the next monsoon approaches, possibly as the animals prepare to shift from drift feeding to rock browsing. Gut indices did not show a conspicuous cyclical pattern. Tetracycline tagging was used to determine growth rate constants (K) for pre-and post-monsoon periods. K is significantly higher after the monsoon (K=0.57/yr) when food is more abundant and growth and reproduction are favoured.
