Spatiotemporal variation in postlarval recruitment of the Caribbean spiny lobster in the central Bahamas: Lunar and seasonal periodicity, spatial coherence, and wind forcing

Abstract

A large-scale recruitment study of the Caribbean spiny lobster Panulirus argus in the central Bahamas identified (1) strong spatial coherence in settlement to inshore nursery habitats, (2) temporal variability due in part to stochastic wind forcing, and (3) lunar and seasonal periodicity in settlement. First, we quantified lunar variation in settlement on standardized artificial substrates to determine whether or not intra- and inter-annual variability in recruitment could be adequately described by measuring influx of postlarvae during the first quarter of each new moon, as suggested by previous studies. Next, we compared settlement data obtained from artificial surface substrates to concentrations of postlarvae in the water column and benthic settlement. Long-term (6 yr) spatiotemporal variation in postlarval settlement was then quantified at 8 sites spanning a longitudinal and onshore distance of 43 km and 11 kin, respectively. Lastly, we examined the relationship between postlarval settlement and environmental variables with time-series analyses. The key findings were that: (1) significant lunar (first quarter of lunar phase) and seasonal (fall peak) periodicities in settlement were consistent across sites; (2) postlarval settlement varied more across sites (~600%) than between years at a single site (~50%), and inter-site differences were consistent across time (i.e. some sites always had higher settlement than others); (3) settlement was correlated with along-shore winds blowing towards the southeast, but not with cross-shelf winds or water temperature; (4) floating, 'Witham-type' artificial settlement substrates yielded an accurate index of postlarval concentration and flux past a given point; and (5) floating substrates were a relatively poor indicator of benthic settlement, though the relationship between surface and benthic settlement may depend upon benthic habitat availability and postlarval supply. These results indicate that artificial settlement substrates provide a reliable index of postlarval supply to inshore nursery habitats, and that a combination of stochastic and deterministic forces influence recruitment over various scales of time and space.