Researchers at James Cook University in Australia have found a simple and useful way to determine which coral reef fish species can live across the greatest range of depths, according to a release. The key to finding the difference, they say, lies in the shape of a fish’s tail.
Specifically, the caudal fin aspect ratio, a measure of the shape of a fish tail, was found to be the best predictor of the range of a reef fish species. Scientists found that fish with the greatest ranges, or those able to live in both shallow and deep reef habitats, most commonly have forked tails.
Though the researchers are not yet completely certain as to why fork-tailed fish seem to have the greatest ranges, they hypothesize that the difference in tail shape may help to make them swim more silently when compared to fish with non-forked tails. The need to remain stealthy in deeper areas, they note, is incredibly important because of predatory fishes’ reliance on things other than waves or visual cues, brought on by light, to capture prey.
The findings are useful in the face of discoveries of deeper reefs existing in the ocean’s “twilight zone,” an area up to 150 meters deep.