Young humans aren't the only animal to engage in reckless behavior when exposed to controlled substances. Young fish do, too!

A study published this week in the Proceedings of the National Institute of Sciences (PNAS), shows that clownfish and damselfish larvae exposed to elevated levels of carbon dioxide in their larvae state are heedless to the scent of proximate predators.

Scientists are unsure if this behavior stems from CO2 masking the scent of predators in the water, or if the gas actually alters the scent receptors in the fishes' brains.

Regardless of the means by which the behavior is produced, it is the behavior's effect that alarms scientists.

The mortality rate of the test fish skyrocketed due to their increased inability to avoid predators' attack.

If current levels of carbon dioxide persist or worsen, scientists fear many species of fish will face extinction.

Read more:

• High CO2 concentrations can turn fish into daredevils (Ars Technica)
• Replenishment of fish populations is threatened by ocean acidification (PNAS)