February 2012 Expedition - Day 15 - More about BRUVs

We sadly left the northern atolls behind today.  Today belonged to the BRUVers.

The  Pacific Marlin set sail south, heading for some isolated seamounts just to the north of Diego Garcia.  The top of these seamounts are around 70-90 metres deep, so the diving teams have a much appreciated day off. 

Jessica tells the story -

“We left Egmont overnight for what the charts suggest is a field of shallow seamounts, rising from 1000m to less than 100m from the surface, to the northwest of Diego Garcia. We have identified four candidates that rise to between 63m and 94m of the surface ... but we’re not sure they are actually there!  We arrive at the first waypoint at dawn with the Marlin running a search pattern over the area.  Anticipation turns to quiet disappointment as we are unable to find it. But determined, we move to the next location.  Eyes still glued to the echosounder, pinging to 800m, there is a whoop of excitement on the bridge as we start to see the bottom shoaling.  Moving at 2.5 knots, we see in rapid succession 800m, 500m, 200m and then a plateau at about 65m.  We mobilise long ropes, the BRUV rigs and begin dropping across the plateau from the FRC (Fast Rescue Craft) which has been our workhorse throughout this trip in the able hands of Chief Engineer Les Swart.

Twelve BRUV deployments later, with our brawny but exhausted crew having hauled the BRUVS up from between 65m to 85m on a beautifully still but swelteringly hot day, the depths were revealed.  Crystal clear bright water greeted us even at 85m.  The top of this seamount hosted a garden of seawhips, soft corals, and sponges.  Inquisitive silvertip sharks were abundant, a large marbled ray ambushed one of our bait bags, and an abundance of emperors crowded the field of view, with trevally swooshing through.  Moorish idols, pennants flying, danced in and out, undisturbed by so many potential predators.  Our dive master David Tickler also completed a very quick blue-water snorkel which yielded a magnificent photo of six silvertip sharks suspended in a rich blue.  We are very excited about finding this feature as a preliminary assessment suggests it has not been trawled and, according to our Senior Fisheries Protection Officer Andy Deary, its proximity to Diego Garcia means poaching is unlikely.  A perfect place to study pristine fish and shark assemblages!