Limiting factors for queen conch (Lobatus gigas) reproduction: A simulation-based evaluation

Queen conch are among the most economically, socially, and culturally important fishery resources in the Caribbean. Despite a multitude of fisheries management measures enacted across the region, populations are depleted and failing to recover. It is believed that queen conch are highly susceptible to depensatory processes, impacting reproductive success and contributing to the lack of recovery. We developed a model of reproductive dynamics to evaluate how variations in biological factors such as population density, movement speeds, movement restrictions, rest periods between mating events, sexual facilitation, and perception of conspecifics affect reproductive success and overall reproductive output. We compared simulation results to empirical observations of mating and spawning frequencies from conch populations in the central Bahamas and Florida Keys. Our results confirm that low probability of mate finding associated with decreased population density is the primary driver behind observed breeding behavior in the field, although additional factors also play important roles. In particular, sexual facilitation and perception of conspecifics may explain observed lack of mating at low densities and differences between mating frequencies in the central Bahamas and Florida Keys, respectively. Our simulations suggest densities greater than 200 adults/ha are needed for high levels of spawning output, supporting the suggestion that effective management strategies for queen conch should aim to protect high-density reproductive aggregations and critical breeding habitats.