Remember Bruce the reformed shark that swore-off eating fish in the hit movie, Finding Nemo? He's quite a character, and new research from Australia seems to suggest sharks do have individual personalities much like people (and Bruce) do.

A first-of-its-kind study led by researchers at Macquarie University's Department of Biological Sciences has observed individual personality differences in Port Jackson sharks. These are ugly bullhead sharks with bulging foreheads and funny teeth found off the coastal regions of eastern and southern Australia.

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This type of shark isn't known to attack humans but instead eats marine life such as fish, hard-shelled mollusks and crustaceans. Its hard shelled diet explains its strange teeth.

Researchers found that individual Port Jackson sharks had distinct and consistent responses when exposed to an unfamiliar environment and stress. Researchers conducted trials to test the sharks' boldness to test this observation.

They said a shark's boldness measures its willingness to take risks. It also influences a shark's health through its correlation with stress hormones and associated physiological profiles.

The Port Jackson sharks were first placed in a tank provided with shelter and timed to see how long it took each shark to emerge from the shelter and into a new environment. The second behavior test saw each shark undergo a stressful episode before the sharks were released again. Researchers observed how quickly the sharks recovered from these stresses.

The results revealed each shark's behavior was consistent over repeated trials, indicating ingrained behaviors instead of chance reactions.

The trials showed some sharks were consistently bolder than others. It also revealed the sharks most reactive to handling stress in the first trial were also the most reactive in a second trial.

"We are excited about these results because they demonstrate that sharks are not just mindless machines. Just like humans, each shark is an individual with its unique preferences and behaviors," said Associate Professor Culum Brown.

He said the main thing that emerges from this work "is that each shark is an individual, with predictable behavioral responses to certain events. Brown said this means that when people and sharks interact, each shark is going to respond to that interaction differently.

"Our results raise a number of questions about individual variation in the behavior of top predators and the ecological and management implications this may have. If each shark is an individual and doing its own thing, then clearly managing shark populations is much more complicated than we previously thought.

"Understanding how personality influences variation in shark behavior -- such as prey choice, habitat use and activity levels -- is critical to better managing these top predators that play important ecological roles in marine ecosystems."

TagsPort Jackson sharks, Macquarie University, Culum Brown.