Marine monitoring program: placement of fixed transects

Carrying the concrete blocks

Arjan and Jennifer who work at GIF headquarters in Mahé landed on Denis Island last Tuesday to install fixed underwater transects for the marine monitoring program. Our aim was to set out transects at 4 site location around Denis Island to standardize collection of data on the reefs over the years. 

Unfortunately in typical island fashion; things didn't quite go according to plan. On Tuesday afternoon the boat engine failed which meant the survey would have to wait until Wednesday morning. We did however enjoy a few drinks on Tuesday night as the whole GIF team was together for the first time since Tommy and I had begun out volunteer placement (although we never really need a reason to have a few beers after work).

Manta tow to find the most suitable site

We met at the Dive Centre on Wednesday morning at 8am, which meant an extra hour in bed so no complains here. Luckily, there were no guests booked for a morning dive so we were allowed to use the dive boat which was an added bonus. Arjan, Jennifer, Martijn, Tommy and I set off for our first dive location ‘Batfish’ with our friendly skipper; fortunately I completed my Padi Open Water Qualification last year so I was able to assist with the marine work that required scuba diving. 

We used 2 concrete slabs to mark each end of the 50 metre transect, Jennifer took the tape measure at swam 50 metres out from the first marker point, I followed laying down a rebar every 10 metres and making sure the transect line was as straight as possible. Martijn and Arjan hammered in the rebar at each of the 10 metre intervals until we had finished. I was happy enough marveling at the expanse of coral and beautiful tropical fish that were swimming around.

Laying out the transect

As we were about to begin our ascent we saw a juvenile whale shark, somewhere between 5 and 6 metres long swimming majestically above us!  In the few seconds we watched the world largest fish swim by, I probably used up around a quarter of the air in my tank I was that excited. As the whale shark was beginning to pass by we noticed that the boat was heading in our direction. At first I figured the boat would drive the shark away but what happened next wouldn’t have looked out of place in a David Attenborough documentary. A pod of around 6 or 7 bottlenose dolphins had been following the boat and suddenly headed straight for the whale shark in an attempt to drive it away. The shark seemed completely relaxed and unimpressed as the dolphins’ actions as it slowly disappeared into the blue abyss.

Some more heavy lifting underwater

We lay out another 50 metres transect at the next dive site ‘Boulders’ before heading back for lunch. Everyone was buzzing to tell their own version of events that had occurred that morning. Tommy had seen the pod of dolphins from the surface so we had a story from all angles and no one seemed that tired of telling. Janske, who had been busy with a nature tour in the morning took my place for the afternoon as they lay down a transect at the final dive site ‘Aquarium’. It was nice for everyone to take part in the marine work as it was a welcome break from the usual routine. We also welcomed the arrival of Arjan’s father Jan (who is currently volunteering on Mahé) for his first visit of Denis.

On Thursday morning torrential rain prevented us from starting the last transect, but we did go on a short island tour to show Jan around. In the afternoon, when the weather had improved, we set up the final transect on ‘House Reef’ just out the front of the hotel. Although it was only about 2 metres deep we used the scuba equipment as we needed to stay under water for long periods of time. Jennifer, Arjan and I set up the transects with Tommy and Jan following behind in the kayak. The kayak was a blessing as it could carry all the heavy equipment such as the camera and the rebars to the site. The shallow water and strong current made it very difficult to hammer in the rebars and we were often fighting hard to stay in the same place whilst being aware not to damage any of the surrounding coral. 

Hammering in rebar

By the time evening came, everyone was exhausted but happy that all the transects had been set up. Early April marks 10 years since the start of GIF and given the entire team were on Denis it made sense to celebrate the anniversary a little early. We were invited to spend the evening at Janske and Martijn’s house. Janske and Jennifer as made cookies and baked a cake to mark the anniversary. Even Mr. Mason brought along a few rock cakes when he joined later on, Tommy and I were all too happy to drink as eat to our hearts content.

On Friday we said goodbye to Arjan, Jennifer and Jan as they flew back to Mahé, thus ending what was my favourite week on the island so far. At times the work may be tough and the mosquitoes are a pain but when you get the chance to swim up close with the likes of whale sharks and dolphins, nothing else seems to matter. 

Concrete block with marker buoy

Nick from England (GIF volunteer)