Editor’s Note: Cocos Island National Park, Costa Rica is located 350 miles from the mainland in the Pacific Ocean and is a U.N. World Heritage Site. The waters of Cocos are highly diverse and have one of the highest biomasses of fish found anywhere in the world. It is also an important no-fishing sanctuary for many species of highly migratory species including large populations of hammerhead and other sharks. Turtle Island is involved in a study of its marine fauna focusing on sharks and turtles. This is blog 3 of 4 from the expedition. Photos and videos provided by Edwar Herreno. Read blog 1, and blog 2.
Some of the most fascinating places underwater are fish cleaning stations. These are locations where fish and other marine life congregate to be cleaned of parasites, dead skin cells, and bacteria by other marine species, often by smaller fish. Shark cleaning stations are one of the highlights of diving Cocos, where, in specific locations, butterfly fish and angel fish congregate and wait for hammerhead and other sharks species to come in for a thorough cleaning. It sometimes seems that hammerheads, Galapagos, and black-tip sharks line up for their morning clean-up and display specific behavior by greatly slowing swimming speed and/or nearly becoming motionless, flaring their gills to allow cleaner fish access and opening their mouths. This cleaning process is an example of mutualistic symbiosis, meaning that both parties (the cleaned shark and the cleaner fish) benefit from the interaction.
These are also excellent opportunities for researchers to tag these sharks, who seem to hovering in bliss, allowing us to get close enough (approximately two feet) to attach acoustic tags using a “Hawaiian sling” spear pole.
Summary of Data Collected: Over our 7-days/21-dive research schedule, we managed to tag eight hammerhead sharks, two Galapagos sharks, and one silky shark. We also collected nine tissue samples for genetic and stable isotope analysis from hammerhead and white-tip reef sharks, and photographed and videotaped hundreds of sharks for photo-id analysis. Shark and ray relative abundance surveys were also conducted on nine dives as part of our long-term monitoring protocol. Only two turtles were observed: one hawksbill being targeted by a tiger shark; and one unidentified species that surfaced briefly to breathe and then quickly disappeared. Mark Stabb identified 91 different species of fish on this trip, including one not currently listed as occurring at Cocos Island.
Interested in joining our next expedition? Learn more here!