Divers on the Reef: The Fish Get Used to Us — Sort Of

Shrimp, Pederson, Anemone Bon 08 4391

The study focused on Pederson’s cleaner shrimps like these that were associated with corkscrew anemones (not “giant” anemones like this one).  They observed the shrimps cleaning some 20 species of fishes. RF Photo.


SCUBA DIVERS HAVE AN IMPACT ON FISH BEHAVIOR when they dive on tropical reefs, but the fish get used to it – somewhat, a study has found.

While most research on animal behavior involves direct human observation, it’s supposed to have neutral impact on the behavior. A question is whether this can be the case underwater, where scuba divers arrive suddenly on reefs with noisy, bubble-spewing air systems. An assumption has generally been that the fishes and other reef life become accustomed to it and carry on as normal.

A team of scientists in the U.S. and U.K. decided to test this, focusing on cleaning behavior at two reefs in the Bay Islands off Honduras — a long-dived reef at the island of Utila and a reef protected from divers in the nearby Cayos Cochinos Marine Protected Area (CCMPA). They took three approaches in their fish-watching: up-close observation, observation at a distance and remote video recording.

Short Answer: Diver presence does affect behavior. The animals they observed up-close on the frequently dived reef did engage in cleaning behavior four times as much as at the protected reef, suggesting the animals had acclimated. But the rate of cleaning interactions at the Utila reef was still significantly lower when divers were present than when they were absent.

Their findings were published in PLOS One, the online research journal. To read this study, click on: Do Reef Fish Habituate to Diver Presence? Evidence from Two Reef Sites with Contrasting Historical Levels of SCUBA Intensity in the Bay Islands, Honduras,” Benjamin M. Titus, Marymegan Daly and Dan A. Exton, Published: March 25, 2015 DOI: 10.1371/journal.pone.0119645.