Newly discovered deep-water nursery and spawning habitats of the queen conch Aliger gigas in Puerto Rico

The queen conch Aliger gigas is a large marine gastropod and sustains one of the most important fisheries in the Caribbean. Overfishing of queen conch has led to shifts in the distribution and abundance of this species in some Caribbean countries; as a result, fishing effort has been redirected to deeper waters (>25 m), where fishers have largely switched from harvesting conch by snorkeling to using SCUBA. Advances in technology such as camera sleds have been used to identify, measure, and study queen conch in shallow habitats, but only sparingly in deeper habitats that may serve as refugia. To define deep-water habitat use and composition, we used a camera sled to quantify siphonal length, life stage, and environmental characteristics of the queen conch on the west coast of Puerto Rico. We conducted multiple 2 h transect surveys at 25-45 m depths during summer 2018. Queen conch densities ranged from 2.6 to ~3000 ind. ha -1 , with relative abundance highest at the 27 m depth interval. A novel finding was the discovery of deep-water nurseries and aggregations of juvenile queen conch in association with deep-water spawning grounds at the 27 m depth interval. Densities in deep-water habitats rivaled those in shallower habitats and indicate that deep-water nursery and spawning habitats warrant management measures for sustainable exploitation as well as integration of these habitats into metapopulation dynamics.