Abstract

Relationships between density of mature adults and mating frequency in queen conch were observed at three sites in the central Bahamas including one no-take marine reserve (Exuma Cays Land and Sea Park) and two historically important fishing grounds (Berry Islands and Andros Island). No mating was observed in any one count with density < 47 adults/ha, which is consistent with the established occurrence of a mate-finding Allee effect in queen conch. The unfished reserve site had larger and older conch with 10% of adults mating, and mating frequency increased rapidly with adult density. Logistic modeling showed that a 90% probability of mating occurred at 100 adults/ha. Mating frequencies increased more slowly with density on the fishing grounds, with 5.9% of the adult population mating in the Berry Islands and only 2.4% mating at Andros Island. A 90% probability of mating required 570 and 350 adults/ha, respectively, at those fishing grounds. Higher densities required for successful mating in the fished areas were associated with numerical dominance by small but thick-shelled adults representing a shift in population structure that is likely the result of selection imposed by fishing pressure. Lower mating frequencies were observed in populations dominated by this small adult phenotype, compounding the density effect on reproduction. Because releases of hatchery-reared queen conch have not been successful, preserving the integrity of spawner density and population structure will be critical for conch conservation.