Oil-exposed fish make dangerous decisions, study finds

Fish on a coral reef Image copyright Jodie Rummer
Image caption Oil-exposed fish are slow to respond to danger, the study found

Small amounts of oil can cause coral reef fish to engage in risky behaviours, according to a new study.

Researchers liken the responses of oil-exposed fish to being intoxicated, and say it endangers their lives.

The study found the fish often swim towards open waters, have trouble selecting suitable habitats and are slow to respond to danger.

Pollution impairs their ability to survive in key environments like the Great Barrier Reef, the authors said.

The international study monitored what happened when six species of fish were exposed to oil in their first three weeks of life.

The equivalent of even a few drops of oil in a Olympics-size swimming pool created "dramatic alterations" in behaviour, according to the researchers.

Image copyright Getty Images
Image caption The research involved fish living on the Great Barrier Reef

"Our oil-exposed fish were not making good choices," co-author Dr Jodie Rummer, from James Cook University, told the BBC.

"They were choosing [to settle in] open water or piles of dead coral. These types of choices would make them much more vulnerable to a predator."

Survival fears

When researchers simulated a predator attack, the fish were sluggish to respond and did not move in the right direction.

"The fun, quirky way that we have described this whole response is like being drunk - you are making poor choices," said Dr Rummer.

"That is exactly what these fish were doing."

Dr Rummer said such decision-making could compromise fish populations and the overall health of coral reef systems.

"The effects of the oil concentration lingered because we saw decreased growth rates and also a decrease in survival," she said.

"It is not like they got used to it - they did not up their tolerance for gin and tonic - they got worse over time."

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