Habitat selection by post-settlement juvenile stone crabs (Menippe mercenaria) and predation risk in shallow near-shore habitats

Abstract

Characterizing habitat selection of the stone crab Menippe mercenaria (Say) provides crucial information for the successful management of this commercially important fishery in Florida. The post-settlement juvenile stage of the stone crab lifecycle faces unique environmental, physiological, and survival challenges prior to becoming sexually mature, yet little is known about their preferred habitat. Our study focuses on post-settlement juvenile (< 1 year, 2–20 mm carapace width) habitat selection between structured artificial seagrass, structured oyster shell rubble, and non-structured sand habitats in the laboratory. Our laboratory experiments provided a unique opportunity to uncouple chemical and environmental cues from the structure of habitats, allowing the study to focus predominantly on the effect of structure on habitat selection. In the controlled laboratory environments, post-settlement juvenile stone crabs preferred structured habitats (artificial seagrass and oyster shell rubble) over non-structured habitats (sand). Survivorship across all trials was high (97%). The laboratory experimental results were complemented with a field predation risk experiment in comparable shallow, near-shore habitats. During the field experiments, predation risk was highest in structured oyster shell rubble and lowest in structured vegetated seagrass. In the seagrass habitat, post-settlement juvenile stone crabs experienced 33% mortality. The sand and oyster shell rubble habitats experienced 69.3% and 83.3% mortality respectively. The data presented here indicate that stone crab juveniles prefer structurally complex habitats and have higher survival in comparable natural habitats. Our results suggest that structurally complex habitats (i.e., seagrass beds) may provide better nurseries for post-settlement juvenile stone crabs and that seagrass restoration or preservation efforts may improve stone crab post-settlement survivorship possibly allowing new recruits to enter the stone crab fishery.