Bryan McAllister’s personal reference notebook
September 12, 2026Short & citedBlog
Civic Viewpoint.
A quiet encyclopedia with a personal desk
Kept by Bryan McAllister — short guides, clear facts, and the Canadian angle when it matters.
Field Notes • Biology

Bull shark

The bull shark (*Carcharhinus leucas*) is a species of requiem shark found in warm coastal waters, estuaries, and rivers.

Updated September 12, 20261 min readCited sources

The bull shark (*Carcharhinus leucas*) is a species of requiem shark known for its ability to tolerate both saltwater and freshwater. It is often associated with unprovoked attacks on humans, though such incidents remain rare.

What it is

The bull shark belongs to the requiem shark family Carcharhinidae. It is also known regionally as the Zambezi shark or Lake Nicaragua shark. Females generally grow larger than males, reaching typical lengths of 2.1–3.5 m and weights of 90–230 kg.

Where it lives

Bull sharks are euryhaline, meaning they can live in both saltwater and freshwater. They inhabit warm coastal waters, estuaries, and rivers worldwide, and can travel far upriver. This adaptability makes them one of the few shark species found in freshwater systems.

Why it matters

Bull sharks are widely described as aggressive and are among the shark species most often implicated in unprovoked attacks on humans. However, attacks remain uncommon relative to the number of sharks and human water use. For Canadian readers, the species is relevant through marine biology, shark conservation, and public interest in shark behaviour and safety.

In short

  • Bull sharks can live in both saltwater and freshwater (euryhaline).
  • They are found in warm coastal waters worldwide and can travel far up rivers.
  • Their diet is broad and opportunistic, including fish, rays, turtles, and other sharks.
  • They are often linked with human attacks, but such incidents are rare.
Canadian angle

Bull sharks are not native to most Canadian waters, but they are relevant to Canadian readers through marine biology, shark conservation, and public interest in shark behaviour and human safety.

Quick questions

How aggressive are bull sharks?
Bull sharks are widely described as one of the more aggressive shark species, but much of this reputation comes from their bold behaviour and frequent overlap with people rather than from frequent attacks.
Can bull sharks live in freshwater?
Yes. Bull sharks can tolerate both saltwater and freshwater and may spend long periods in rivers, estuaries, and lakes.
Are bull sharks dangerous to humans?
Bull sharks are considered potentially dangerous because they are large, powerful, and often live near people, but unprovoked attacks are still rare.

Sources

  1. IFAW — https://www.ifaw.org/animals/bull-sharks
    Supports: Freshwater and saltwater tolerance; dangerous to humans; general facts on habitat and attacks.
  2. National Wildlife Federation — https://www.nwf.org/Educational-Resources/Wildlife-Guide/Fish/Bull-Shark
    Supports: Freshwater tolerance; typical size; danger to humans; general biology.
  3. National Geographic — https://www.nationalgeographic.com/animals/fish/facts/bull-shark
    Supports: Aggressive reputation; habitat near shorelines and rivers; human interactions; diet context.
  4. A-Z Animals — https://www.a-z-animals.com/animals/shark/shark-facts/most-aggressive-sharks/
    Supports: Aggression claims and attack statistics cited in search results.
  5. Australian Geographic — https://www.australiangeographic.com.au/nature-wildlife/2021/07/bull-sharks-fact-from-fiction/
    Supports: Aggression explanation; curiosity versus targeted aggression; human encounters.
  6. Wikipedia — https://en.wikipedia.org/wiki/Bull_shark
    Supports: Scientific name; common names; broad habitat description; euryhaline nature.