Effects of gasteropod predation on the reproductive output of an overexploited deep octocoral

The study presented herein is aimed at quantifying the effects of the partial predation exerted by the gastropod Pseudosimnia carnea on the reproductive features of the highly valuable, slow-growing, and long-lived red coral, Corallium rubrum. Seventy-five colonies were collected just before annual spawning from a red coral population living between 85 and 90 m deep in the NW Mediterranean; of these, 35 % were affected by P. carnea. Female colonies were more frequently preyed upon than males (3:1 ratio). Overall, 1,100 polyps were dissected and examined for their reproductive content. The mean number of polyps per colony and the mean fecundity of female polyps and colonies were significantly reduced by gastropod predation, which affected colonies independently of their size; in particular, colony fecundity was reduced by 81 %. The consequent reduction in population reproductive output is likely to have long-term effects on preyed-upon populations and thereby limit their resilience to intense commercial harvesting.