SEXUAL REPRODUCTIVE EFFORT IN THE MEDITERRANEAN GORGONIAN PARAMURICEA-CLAVATA

Sexual reproductive effort in the Mediterranean gorgonian Paramuricea clavata was studied from 1990 to 1993 in a population dwelling at a de pth of between 17 and 19 m off the Medes islands (northwestern Mediter ranean). Variations in polyp fecundity with sex, polyp position within the colony, and colony size were studied, as was interannual variabil ity. Onset of sexual maturity was on average delayed until colonies ha d attained a size of 20 (11 to 30) cm, i.e. an age of 13 (6 to 19) yr according to our estimates. Male and female colonies of P. clavata rip ened synchronously and bore fertile polyps on nearly all branch orders . However, the percentage of fertile polyps and the number of gonads p er fertile polyp decreased as branch order increased. Accordingly, rep roductive effort was highest for polyps on first-order branches, which contributed 85% of the entire production of gametes. Reproductive eff ort increased exponentially with colony size due to increases in the p ercentages of fertile colonies and polyps and in the number of gonads per polyp, at least to a size of 35 cm in height. No significant inter annual variation was detected over the 3 yr study period. The gorgonia ns present on a representative plot with a surface area of 1 m(2) prod uced, on average, 2 x 10(6) sperm sacs (9 g dry wt of male sex product s) and 7 x 10(5) eggs (7 g dry wt of female sex products). Total repro ductive effort was on the order of 9 g C m(-2) yr(-1).