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Days 5-6, Bouncing Between French Frigate Shoals and Gardner Pinnacles
Afternoon of May 24, 2006
by Dr. Malia Rivera

Swimming with hundreds of ulua at Rapture Reef. Photo by Malia Rivera.

A second day off the still waters off French Frigate Shoals proved fruitful for our team of scientists who were busy taking advantage of the calm weather. “Team Fish”, the group of four biologists studying population genetics of surgeonfish, butterflyfish, wrasses, blennies, and the introduced snapper Ta’ape gathered samples from Rapture Reef, one of the most beautiful sites of the entire Archipelago. The shark team also radio tagged a few sharks.

Rapture Reef. Photo by Luiz Rocha.

Because of the good weather and low winds, the Commanding Officer of NOAA Ship Hi‘ialakai, after being advised by chief scientist Randy Kosaki, decided to press onward to Gardner Pinnacles, a short 120 nautical miles northwest and just a night’s ride away. Notoriously rough with high currents, Gardner is a tiny rock shrouded by hundreds if not thousands of seabirds and wreaking of decades of guano buildup. Because of its small size, there is very little lee generated, making it extremely difficult for diving.

I spent the day with the shark team and had my first encounter with a Galapagos shark. When the fish team deploys, they tend to attract the curiosity of these stealth predators, who sneak in and out stealing peeks of our activities. As the dive went on, we spent the afternoon with one shark, then four, then over a dozen. Toward the end of the second dive, large Ulua started in, and combined with the unpredictable currents, we had to call the day early.

Invertebrate biology team preparing to dive at Gardner Pinnacles. Photo by Randy Kosaki.

The fish team, lead by Dr. Brian Bowen and accompanied by post-docs Matt Craig and Luiz Rocha are studying migration and gene flow of Hawaii’s reef fish. Much of the work on the NWHI at HIMB uses genetics to explore these types questions. Figuring out just how populations of organisms are moving from one island to the next, and the next, and ultimately across the entire archipelago, can be determined by looking at genetic relationships from fish sampled from these various geographic regions. Dr. Bowen’s lab back at HIMB extracts DNA material from tissues collected in the field, and using a technique call PCR, makes millions of copies of small pieces of the genome. The pieces, in large copy numbers to facilitate laboratory manipulation, are made for every single tissue specimen obtained from each fish, and then compared to each other. The more alike the genetic material, the more “related” each fish is. When you lay this type of data over the geographic areas they were sampled from along the archipelago, you can begin to piece together the puzzle of how close together or how far apart in space, or islands, each fish within a species lies. What this can tell us, and why it is useful for management, is just how far young fish larvae are traveling after they emerge from their eggs. Are they staying where their parents are from, or are they drifting far distances to grow up at a different atoll or island? With this type of information in hand, it will be easier to devise management strategies to protect reef fish resources.