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The silky shark, Carcharhinus falciformis (Müller and Henle, 1839), is a large circumtropical, oceanic, and coastal-pelagic species whose spatial ecology is not well understood. In Cuba, silky sharks are captured in local fisheries and are subjects for shark-based diving tourism off the Caribbean coast. Our study tracked three female C. falciformis (ranging 174-200 cm precaudal length) using satellite-linked tags to characterize the movement patterns and behavioral ecology of this species off the southeast coast of Cuba. Field work was conducted in the Jardines de la Reina (Gardens of the Queen) archipelago and utilized a novel inwater method for attaching pop-up satellite archival tags to free-swimming sharks. Results from both archival and position-only tags suggest the sharks traveled <30 km from the tagging site during the month-long deployments. The depth and temperature ranges recorded for two specimens were 0-640 m and 11.5-27.5 °C. Time-at-depth/temperature data revealed preferences for the upper-mixed layer (down to 150 m) and a temperature range of 24-27 °C. A diel vertical movement pattern was observed with silky sharks spending greater time at depth during the day than at night. Plasticity of vertical habitat utilization was noted with occasional forays to depths in excess of 550 m during both day and night. Daytime forays to surface waters were also observed and were most common during the morning hours between 09:00 and 11:00, possibly due to the ecotourism industry's use of bait during that time to attract sharks to the dive area. [ABSTRACT FROM AUTHOR]

Dispersal varies among species according to different biological and environmental factors. It is known that there is strong genetic division between the Ocean Surgeonfish ( Acanthurus tractus) and the Barber Surgeonfish ( Acanthurus bahianus) in the Caribbean and southern Atlantic biogeographic provinces with relation to the Amazon-Orinoco outflows. We analyzed cytb gene sequence diversity from 149 individuals collected at five localities around Cuba between October 2006 and February 2010. As expected, most individuals had haplotypes identical or closely related to those previously reported for the Caribbean. However, south Atlantic lineage haplotypes were also found in all surveyed localities with frequencies around 5 %. This finding suggests that A. bahianus has dispersed in recent times across the Amazon-Orinoco barrier, probably because environmental perturbations have aided dispersal. [ABSTRACT FROM AUTHOR]