Bull shark (Carcharhinus leucas) is a large coastal requiem shark famous for its ability to live for extended periods in low‑salinity and even fresh water. It regularly ascends river systems and may occupy inland lakes (e.g., Zambezi River, Lake Nicaragua). Its proximity to human use areas elevates conflict risk. Global IUCN status: Near Threatened (NT).
Ecology & Reproduction
Placental viviparous; females use estuaries, lagoons and shallow coasts as nursery areas. Reproductive cycle ~1–2 years, gestation ~10–11 months, litters 1–13 (often 6–10). Diet broad: bony fishes, elasmobranchs, crustaceans, cephalopods, birds and small marine mammals.
Identification
Stout body with a short blunt snout; large triangular first dorsal fin; grey dorsum and white ventrum with dusky fin margins. Teeth thick with fine serrations for cutting.
Osmoregulation
Maintains osmotic balance across salinities via kidney/rectal gland function and urea/TMAO regulation, enabling long residence in fresh water—rare among large sharks.
Threats & Conservation
Fishing pressure: target and bycatch in longlines/gillnets; fin and meat trade.
Habitat loss: pollution and dams altering estuaries/river connectivity and mangroves.
Human–shark conflict in nearshore waters leading to culls or lethal control.
Priorities: spatio‑temporal protection of nurseries, gear modifications (mesh size/weak links), best‑practice live release, and targeted risk communication in high‑use river/estuary reaches.
