Monday, June 04, 2007

Close Encounters at Maug Islands

It was our first day at Maug, near the northern extreme of the Marianas Archipelago. The three wall-like (~800 ft tall) islands that comprise Maug form the rim of an ancient volcano, with three passages to a deep (to nearly 1,000 ft) lagoon or submerged caldera. These high islands are spectacularly scenic, with a pre-history feel. Our first dive was fairly routine- a seascape of large volcanic boulders, with small colonizing corals, scattered across black sand. The coral reef on our second dive, outside of North Island, was simply gorgeous- one of the best in the Marianas- high cover of diverse, large multi-colored corals, abundant fish of all sizes, and great visibility, nearly as good as it gets underwater. I was conducting stationary point counts of medium-large fish on the seaward reef slope, while my buddy did the same a short-distance shoreward. After recording a few large fish, I noticed a shark swimming straight at me. I didn’t realize its size till it turned just in front of me- a 5-foot gray-reef shark (Carhcarhinus amblyrhynchus), followed closely behind by another fat 6-footer, as well as a giant trevally (Caranx ignobilis). As I recorded these on my data sheet, I noticed them swimming around me. My first impression was- wow- great photo opportunity. As I prepared my camera I began moving backwards to fit them in the frame. The one closest to me was then swimming on its side with its body contorted and shaking. I then thought- poor thing, it must be sick or something. It had been some time since I had seen many grey reef sharks, as they seem to becoming rarer each year in the remote Pacific Islands. As I quickly fired a few shots with my camera, I had a flashback of my earlier years of diving with these grays in the Northwestern Hawaiian Islands: the shark was exhibiting aggressive pre-attack posturing behavior! As it opened its jaws wide while violently thrashing his head back and forth, I immediately began moving back toward my dive buddy. The sharks then left. The remainder of the dive was less eventful, with only a 5-foot white-tip shark (Triaenodon obesus) and several great barracuda (Sphyraena barracuda), plus all the other beautiful marine life that comprised this healthy coral reef ecosystem.

Text and photographs by: Bob Schroeder, Chief Scientist


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