Reef-use and residency patterns of a baited population of silky sharks, Carcharhinus falciformis, in the Red Sea

Many shark populations are experiencing critical declines from overfishing, triggering potentially detrimental cascade effects on marine ecosystems. Silky sharks, Carcharhinus falciformis, have experienced some of the most severe declines, yet little information exists on their behavioural ecology to inform management decisions. In the present study, the movement patterns of a sexually segregated subpopulation of female silky sharks on reefs in the Central Red Sea were investigated using acoustic telemetry to characterise habitat-use and residency patterns. Frequent baiting of sharks at a particular reef-site significantly increased time spent in the vicinity, although no increases in use of other reef areas 5–10 and 50–60 km away were recorded, and regular use of all three reef areas persisted in the absence of bait. Observed residency patterns varied considerably, from being present almost year-round to visiting only intermittently. The sharks spent significantly longer times at study reefs during daylight hours, even within bait-free regions, suggesting the diel bias is normal. This pattern became less distinct nearer the full moon when there is more ambient light. The regular, perennial use of these reefs by mature and near-mature female silky sharks highlights the importance of this habitat in the Red Sea for recruitment into the local shark population.