Sharks & Sharks With Flat Tails

We are at Pearl & Hermes atoll, in the middle of the last day of dive ops!  Tonight we will steam overnight to Kure and begin full days of dive ops tomorrow (Monday) morning.

Boat launch from the Hi’ialakai.

A number of technical and political issues are arising.  We expected this so are not too stressed, but we’ve had to be very flexible as our schedule changes all the time.  Most notably, the biggest dive boat (8 diver capacity) is out of commission, presumably for the rest of the cruise.  We are also learning what it is like to be at the very bottom of the planning and scientific food chain.  We are not NOAA divers (so we are here as guests), not paying for the cruise, and are also brand new to cruises in general and the leaders of this cruise in particular.

Lauren excited to see some pomacentrid damselfish. Pomacentrids are very loud – their ‘chirping’ can be clearly seen around dusk on Simon’s recordings.

Fortunately, and somewhat amazingly considering all that, we are still able to get out and collect data!  We had a full day of diving on Thursday, where we found a site in the lagoon (there were huge swells that prohibited any diving or small boat ops on the outside) and set up all of our equipment to record.  On the way out we encountered a couple of squalls with 40 knot winds!  Our small boat turned tail to the wind to ride it out, it was truly amazing to see.  I never thought I would be wearing full wetsuit along with foul weather gear and grateful for that combination.  Thanks mom, for buying me the nice raincoat that is both water and wind repellant!  I have truly used it on this trip.  The rain flattened out the swell and chop, it looked amazing and surreal.

Squall at Pearl and Hermes. All of a sudden, the rain hit us like hail and the winds were shrieking! Luckily its nice and warm.

On our off day, the sun finally came out!  We spent awhile on the bow watching for flying fish and seabirds.  We also went out Friday night to look for the meteor shower.  We only saw 3 shooting stars during about half an hour. There were reports that last night was more successful so we are hoping to try again tonight if we are not too tired.

A brown booby flies past the Hi’ialakai.

Yesterday was an amazing day.  We recovered all of the acoustic and camera equipment in record time, and had two full tanks to spare.  While we took a break for lunch, we saw what looked like a shark in front of the boat. Looking closer, Simon exclaimed that it was a shark with a flat tail! A pod of 40 or so dolphins were playing in the swells and in the bow wave of our boat.  At our coxswain’s suggestions, we jumped in on snorkel to check them out and spent a happy 20 minutes chasing dolphins, who were chasing our small boat to play in its wake, as it drove in circles around us.  Simon noted that he was glad they showed up after we pulled out the recorders since they would have corrupted all of the ambient noise he was trying to capture 🙂

Dolphins at Pearl and Hermes Atoll.

We did our final two dives at two new sites on our way back to the Hi’ialakai.  The first site was amazing, and was actually what we had been expecting all along.  There was a reef with relatively low, but clearly present, live coral cover.  As soon as we entered the water, we were surrounded by schools of giant trevally and watched 5-10 gray reef and Galapagos sharks cruise past.  None of this megafauna were remotely intimidated by us.  In fact, the trevally followed us around and wanted to check out all of our equipment.  Every time I turned around, I’d see 3-5 of the 30 – 50 kg fish behind me. Every time Simon left something on the bottom the trevally would swim around the object and ‘sniff’ it like a pack of inquisitive dogs. The sharks were slightly more cautious but still curious and rather sneaky. Oftentimes we turned around to see 3 or 4 sharks creeping up behind us, aware that we couldn’t see them. Although this might seem unnerving, none of the sharks were larger than about 6 ft. We left one hydrophone and one time lapse camera at this site. Hope they are still there!

Giant Trevally patrol one of our hydrophone sites.

The second site was a pinnacle that we had spotted on our first day, and marked on the way out on Saturday.  It is a piece of the outer reef crest/atoll edge that is eroding down (there is a gap along the atoll ‘ring’ in the northwest section of Pearl and Hermes).  It rises out of deep water, so we were very excited to check it out.  This site appeared rocky, although we suspect that the rock in question is fossil coral skeleton.  It was mostly covered in various algae, but also had single coral heads distributed about.  It was incredibly steep down to about 50 feet, where it leveled off to sloping sand.  We also saw several reef sharks and giant trevally here!  The coolest part of this dive was surfacing- we slowly swam around the pinnacle and hung out at 5 meters for our safety stop.  The upper part of the pinnacle was really cool, with lots of little caves, crevices, and archways.  We spotted a number of large ark shells (like giant mussels/scallops) and tons of little reef fish near the top.

Grey reef sharks were also interested in our activities.

Since the transit was so long to the first site, we also had a full day for recovery yesterday.  We have an extra day at Pearl & Hermes (4 instead of 3), so we made plans to move the two small hydrophones (which are still running) to a couple of sites closer to the ship.  We wanted data from more lively ecosystems than our original pick.  We planned to pick those up in a quick operation this morning and return the boat for someone else to use for 2/3 of the day.  This plan has changed, since the ship has moved to the south side of the atoll!  This usual lee was raging with huge swells for most of our stay but has finally calmed down today.  This means we’ll have another long transit today BACK to where the ship was originally stationed on the northwest side, and two quick dives to recover the hydrophones.  We will be on our way out after lunch!

Lauren with her photo quadrat. In the foreground is the ‘christmas tree’ – four time-lapse cameras are mounted facing the bottom. These take one photo every 5 minutes to create a series of images that reveal the nightly changes in benthic activity level.
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