July 18, 2017 — Just as one too many cocktails can lead a person to make bad choices, a few drops of oil can cause coral reef fish to make poor decisions, according to a paper published today in Nature Ecology & Evolution. A team of fisheries biologists led by Jacob Johansen and Andrew Esbaugh of The University of Texas Marine Science Institute have discovered that oil impacts the higher-order thinking of coral reef fish in a way that could prove dangerous for them—and for the coral reefs where they make their home.
Examining six different species of coral reef fish, Johansen and the team found that exposure to oil consistently affected behavior in ways that put the fish at risk.
During several weeks when coral reef fish go through their juvenile stages of development, they are especially vulnerable. Even in healthy populations of reef fish, typically less than 10 percent of embryos and larvae reach adulthood. Those who survive must learn to identify friend from foe and adopt protective behaviors, such as traveling in groups, minimizing movement in open waters and swimming away quickly from danger.
In experiments, the scientists found that juvenile fish exposed to oil struggled on all these counts.
“In several different experiments, the fish exposed to oil exhibited very risky behavior, even in the presence of a predator,” said Esbaugh, an assistant professor of marine science.
The scientists also found that oil exposure negatively affected the fishes’ growth, survival and settlement behaviors (their ability to find a suitable habitat).
Oil concentrations are found in oceans worldwide, but until now little has been known about the impact of oil exposure on coral reef fish. Earlier research that explored how oil affects the physiology of fishes has demonstrated developmental heart deformities and associated cardiac functions, but this is the first study to demonstrate that oil exposure affects behavior in a way that increases predation and reduces settlement success.