Bull Shark

IUCN

Scientific Name：Carcharhinus leucas

Basic Information

Scientific classification

name：Bull Shark
Scientific Name：Carcharhinus leucas
Outline：Large Fish
Family：Carcharhinidae Carcharhinus

Vital signs

length：F 2.2–3.3 m; M 2.1–2.6 m (larger extremes)
Weight：Typically 90–230 kg (variable)
lifetime：c. 20–24 years (estimated)

Feature

Euryhaline—can inhabit fresh water; placental viviparous; coastal apex predator; estuarine nurseries; higher human‑conflict risk.

Distribution and Habitat

Tropical–subtropical coasts, estuaries, lagoons and rivers/lakes that are accessible from the sea.

Appearance

Stout, blunt‑snouted; large triangular first dorsal; grey above/white below with dusky fin margins; thick serrated teeth.

Details

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.

FAQ

Q1. Can bull sharks really live in fresh water? Yes. Their osmoregulatory physiology allows prolonged residence and feeding in fresh/brackish systems.

Q2. Are they dangerous? Risk is higher than for many pelagic species due to nearshore occurrence and size. Follow local advisories; avoid turbid/crepuscular periods.

Q3. Where are they found? Tropical–subtropical coasts and estuaries worldwide, plus major rivers and some lakes.

Q4. Why Near Threatened? Combined fishing pressure and nursery‑habitat degradation/fragmentation; declines documented in parts of the range.