A new study has revealed that juvenile mahi-mahi exposed to the Deepwater Horizon oil spill have demonstrated a decrease their overall swimming performance by up to 37%.

The study was led by the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science scientists.

“What our study shows is that even a relatively brief, low-level exposure to oil harms the swimming capabilities of mahi-mahi, and likely other large pelagic fish, during the early life stages,” said Edward Mager, UM Rosenstiel School postdoctoral associate and lead author of the study. “If you harm a fish’s ability to swim you also harm its ability to perform actions that are critical for survival, such as catching prey and evading predation.”

In a laboratory experiment, researchers exposed larvae and juvenile mahi-mahi to Deepwater Horizon crude oil to simulate environmental conditions during the 2010 oil spill.

Two groups of mahi-mahi were exposed to crude oil alongside controls exposed to clean seawater. One group was exposed for 48 hours during the embryonic-larval stage and then raised in clean seawater to the juvenile stage, while the other group was raised in clean seawater to the juvenile stage and then exposed to oil for 24 hours. The 48-hour embryonic-larval exposure group resulted in a 37% decrease in swimming velocity as juveniles, while juveniles exposed for a 24-hour period had a 22% decrease in swimming velocity.

Mahi-mahi, also known as dolphin fish, is highly sought after for sport fishing and commercial fishing. Fertilized eggs of mahi-mahi float near the surface of the northern Gulf of Mexico, an area coinciding with the spill zone, where they are believed to remain during their early stages of development.

Another recent study published in the journal of the Proceedings of the National Academy of Science (PNAS) showed that several Gulf of Mexico fish embryos developed serious defects in heart development following exposure to crude oil from the Deepwater Horizon oil spill. The study concluded that, “losses of early life stages were likely for Gulf populations of tunas, amberjack, swordfish, billfish, and other large predators that spawned in oiled surface habitats.”

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