Moorea Reef Sharks Day 4

October 23, 2103

Today was underwater construction day!  We started out with a snorkel in an area near the shark feeding site.  After about half an hour we had the right spot picked out.  We didn’t want to be right at the shark feeding site, but a ways off.  That way we wouldn’t see the effects of a lot of fish being attracted to bait and have to worry about the effects of the divers.  Instead we wanted to be far enough away to avoid those effects but still have higher shark abundances than more “normal” parts of the reef. 

We donned our SCUBA gear and descended with three stakes, a really heavy mallet, and a bag full of the camera housings that we will be attaching to the stakes tomorrow.  It was a good thing we did that test – one of the housings leaked!  But its nothing a bit of silicon can’t fix!  It took us about a half hour to put the three stakes –spaced several hundred yards apart - in at about 50’ depth.  During the dive it was obvious that we were at a good distance for the work.  We saw at least three blacktip reef sharks – a couple of them individuals that Johann recognized from his previous work.  He could tell based on their fin markings.  We also saw three female sickle fin lemon sharks.  They are quite a bit bigger than the blacktips and were cruising slowly along the reef slope.  One of them had fresh mating scars.

The reefs here on the northern coastline of Moorea aren’t what you might expect for a remote island in the tropical Pacific.  Instead of tons of living coral everywhere, on the forereef much of the coral is dead.  A combination of a crown-of-thorns starfish outbreak – which resulted in a lot of coral being eaten – and then a cyclone in 2010 really impacted the reef.  But, everywhere you could see new corals growing as the reef begins to recover.  And, although the coral wasn’t what it will be once it recovers the fish life was really amazing.  We saw what must have been dozens of species in our short dive.

We had to make a quick trip back to CRIOBE to switch tanks and to grab our shark-cam that we want to deploy soon.  This is our advanced camera that should get  60 hours or more of video so we need to make sure that it floats and test how far the VHF signal will go.  Of course, we also managed to squeeze in a nice pasta lunch that Jeremy made…hey, we needed the time between dives!

The second dive was to a site far from shark feeding, but the same depth, basic reef characteristics, and distance from the lagoon pass as the shark site.   It was another amazing dive with well over 100’ visibility (I can’t tell you how much over because I am used to less than 10’)!  We got the three poles in fast and had time for a bit of a tour around the area.  We saw plenty of fish but no sharks in a similar dive time to this morning.  I can’t wait to get the data from these two sites!

Since we had a little time left in the afternoon we tested the advanced shark cam – plenty of range on the transmitter and it floats perfectly!  It will be ready to go tomorrow if we have any luck.  However, we might try our less advanced (and, well less expensive) shark cam tomorrow to see how it goes.  I am excited about a final modification we made to it so it should get great images and data with no disturbance to the shark!

   

Jeremy doing hammering a stake into a small sand patch in the reef.  The bag floating above Johann has the housings for the cameras we will put on the stakes starting tomorrow!

Johann's turn.  

A sicklefin lemon shark cruises through. 

Mike's turn.

Blacktip reef shark.  You can identify individuals by the color pattern of their first dorsal fin.

Moorea Reef Sharks Day 3

October 22, 2013

Today was another amazing day on Moorea.  There wasn’t a breath of wind when we woke up and after organizing gear we were slipping under the bridge – more like squeezing through a tunnel (check out the picture … I am not kidding) - and were out on the bay.  We started out testing the shark-cam.  First step – make sure it floats.  That worked.  Second step – make sure we can hear the VHF transmitter from far enough away.  The VHF sends out a ping that we can hear with a special antenna and receiver that lets us figure out the direction to the transmitter.  Since we won’t be tracking the sharks while they wear the camera, we need a good range or else we might lose the camera.  Luckily it worked great and we had a strong signal more than 3 miles away so we should have no problem finding the package after it comes off a shark. 

The tunnel from CRIOBE to the lagoon

Tracking down the camera system

During the test we ran into a group of spinner dolphins.  There were a couple dozen around and some came over to ride on the bow wake of the boat while others were busy socializing and jumping out of the water, spinning.  The spinner dolphins here spend their days in the lagoon resting and socializing then head out to deeper waters to eat small fish and squid at night.

Spinner dolphins resting in the bay

Some dolphins came to bowride.

We were hoping to catch large blacktip sharks today for several studies.  First, we wanted to deploy the shark cam to see what we might learn.  Second, we wanted to flush the stomachs of sharks to determine what they had been eating.  Third, we wanted to collect blood samples and small clips from fins.  These samples will be used for genetic studies and “stable isotopes” which help us determine where and what the sharks might be eating.  They also give us an idea of whether they eat the same things all the time or if their diets switch as well as how different the feeding habits of different animals might be.  One of our big interests is how different the behavior and feeding is of sharks that visit sites where they are fed by people compared to sharks that don’t live in these areas.

Waiting for the sharks during a brief rainstorm

We started chumming in an area far from the shark feeding site.  We hung a fish head over the side and waited.  After about 15 minutes we saw sharks over the shallow reef chasing fish.  Three sharks were near the surface, their fins out of the water, chasing schools of fish that were jumping to get out of the way.  Unfortunately, they were up-current and had no idea we had bait in the water.   It wasn’t too much longer before a ray showed up and then several blacktips.  We threw a bait to the sharks but we had to keep pulling it away from the ray.   It took a while because the sharks would turn away from the bait at the last second, but we eventually captured a shark - an adult male.  We quickly measured it, collected our samples, and Johann took a picture of its fin.  It turns out you can tell individuals apart by the markings on their fins because they are unique and don’t change over time.  When I tried to put the camera on we realized that we’d have to make some modifications to our soft clamp that holds onto the fin.  Clamps are great – you don’t need to put a tag into the shark – but you have to get them just right or they fall off. It turns out that blacktip fins are a lot thinner than we had thought!   The whole process took only a couple minutes and the shark was back in the water and swimming away powerfully.

We caught a second adult male blacktip reef shark later in the day.  We were able to collect all our samples also flushed its stomach (kind of like they do with people at the hospital if it is needed).  Unfortunately, the only thing that it had in its stomach was the bait it had just eaten!

Waiting for the sharks.

A shark considering whether to take the bait.

Jeremy with the shark that decided he wanted to eat the chum bag.

Collecting blood.

Measuring a blacktip reef shark.

During the day we also tried to catch sharks near the shark-feeding site, but it turned out to be impossible.  The second a bait was in the water it was immediately devoured by a huge swarm of small triggerfish.  The blacktips had no chance!  Jeremy managed to throw tiny scraps of bait in the water to distract the triggerfish for a few seconds but they quickly made their way back to the bait so we had to move back inside the lagoon.

After we got in from the water we worked on gear and samples.  The shark cam is ready to go now…really it is, believe me.  Jeremy and Johann got the samples from the day processed and started working on the stakes for mounting cameras on the reef.  That will make it easy to get a nice sample of reef fish dynamics near and far from shark feeding sites. 

We skipped the nursery area sampling tonight…the tides are way too low.  We will be back out at the nurseries in a couple of nights, though…including with our quadcopter that we are going to use to get counts of sharks. 

Day 2: Moorea Reef Sharks

June 21, 2013

Today was an incredible day.  Linda and I got to relax for a while this morning when Johann and Jeremy made a hardware store run to get supplies for attaching cameras to different parts of the forereef.  We’ll be setting up multiple stations close to shark feeding sites and then a number far from feeding sites.  Hopefully that will allow us to get an idea of how many sharks are in different areas of the reef and how they might influence reef dynamics.  But, before we get started on that we need to get our boat schedule set!   We did get a boat for a little while this afternoon and went for a recon snorkel of the lagoon site where whiprays and blacktip reef sharks get fed. 

It was an amazing couple hours including an awesome boat ride across crystal clear waters in front of stunning cliffs and forests.  When we got to the feeding point, the sharks and rays were waiting for us.  The sound of an approaching boat attracts them quickly and a bunch of rays and a couple sharks were swirling around the boat before the anchor was set.  We had a good time snorkeling with the animals – some of the blacktips were obviously pregnant - and planning our sampling protocols for feeding ecology studies and the cameras that we will be deploying on the sharks to investigate their behavior.  We have two camera systems that will be perfect for these smaller reef sharks!  But that will probably be a project for Wednesday or Thursday.

Once we got back it was time to grab some bait and get set up for another nursery area sampling effort!  Unfortunately the tide was super low so it didn’t work out, but there are plenty more nights to get the samples we need with Jeremy and Johann here for four weeks.  With any luck, tomorrow we’ll be doing our first captures of adult sharks offshore.

Arriving at the feeding site

The rays swarmed the boat before we set the anchor - little did they know we didn't have any food for them!

Whipray and blacktip reef sharks

One of our field vehicles...please pass the duct tape.

Setting up the net for nursery area sampling

A blacktip reef shark next to the restaurant where we had dinner.

Reef Shark Research in Moorea: Day 1

Greetings!  Over the next few days, we will be blogging from Moorea in French Polynesia!  We will be working on a variety of reef sharks – especially blacktip reef sharks, as we investigate their feeding, behavior, and importance to the health of reefs.   I’ll be working with Linda Heithaus, Jeremy Kiszka, and Johann Mourier.   We have a pretty impressive array of tools and goals so it should be a fun trip!  Hope you enjoy!

Mike Heithaus

October 20^th, 2013

Linda, Jeremy, and I were up early after a late arrival in Tahiti.  It took two cars to get us - and all of our gear - to the ferry, but by just after nine we were making the crossing from Tahiti to Moorea.  The water here is amazing – crystal clear– and the vegetation is incredibly lush.   After a bit of a drive, we met up with Johann at CRIOBE and got the lab set up.  Not that anything happened, but if anybody is coming to French Polynesia, remember that even though your iPod charger can handle 240 volts, American power strips usually can’t! 

Most of the day was spent settling in but around sunset we made it to one of the sicklefin lemon and blacktip reef shark nurseries where we will be working.  We set the net but a combination of low water and heavy wind conspired against us.  Still, we did see an adult blacktip reef shark and a ray cruise through after dark.   Tomorrow we should be able to really get started if we can get some bait early in the day!

Waiting in LA...almost time to go!

Waking up in Tahiti

Obviously we need more stuff

Jeremy, Johann, and Linda at the CRIOBE station

Waiting for the ferry

Jeremy and Mike almost to Moorea

Linda and Mike on the ferry

The view from our hotel

Setting the net to catch baby sharks

The local dogs were very interested in the fishing effort...