Negative Consequences of Allee Effect are Compounded by Fishing Pressure: Comparison of Queen Conch Reproduction in Fishing Grounds and a Marine Protected Area
Abstract:Relationships between density of mature adults and mating frequency in queen conch (Strombus gigas Linnaeus, 1758) 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–1, consistent with an earlier study suggesting a mate-finding Allee effect in queen conch. The unfished site had larger and older conch, and mating at that site increased rapidly with adult density, reaching an asymptote at 12%–14% of the population mating at highest density levels. Logistic modeling showed that a 90% probability of mating occurred at 100 adults ha–1. Mating frequencies increased more slowly with density on the fishing grounds; asymptotic mating frequencies were 6.3% in the Berry Islands and just 2.3% at Andros Island. In contrast to the marine reserve, 90% probability of mating required 350 and 570 adults ha–1 at Andros Island and the Berry Islands, respectively. Higher densities required for successful mating in the fished areas were associated with numerical dominance by small, thick-shelled adults. The small phenotype in adults appears to result from selectivity imposed by fishing pressure, and those adults had low mating frequencies, 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.
Document Type: Research Article
Publication date: January 1, 2012
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