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The Pyramids

During the period 2002 - 2003, the Bruneian Fisheries Department deposited a number of concrete pyramids on the seabed offshore Kuala Belait, Jerudong and Muara. The structures were grouped, and consist of two types: a tetrahedron about two metres high, and a five metre high vertically elongated triangular pyramid.

Ostensibly the purposes of these structures is to encourage fish life and to prevent trawling in prohibited areas. That the majority of the pyramids we visited have fishing net remnants caught on them, suggests the latter purpose has been very effective.

A brief note has been written for the benefit of the Bruneian Fisheries Department based on the text and observations below.

On 28th February 2004, at the end of the NE monsoon, Steve Holyoak, Steve Oakley and John Elder dived on Group 64 (Southern Group), a concentration of at least half a dozen of the pyramids lying about seven miles WNW of the Belait river mouth in 15 metres water (1.5 m tide). On descending towards the strong sonar image, we were confronted by that typical Bruneian phenomenon; clear surface waters giving way abruptly, about five metres from the seabed, to a turbid mustard coloured layer of disturbed bottom silt. Poking through this layer could be seen the apexes of several of the pyramids looking just like mountain peaks above a layer of cloud. We chose the closest peak and descended into the murk to investigate.

We had been concerned that this silty layer would reduce the potential for colonisation, however, the disturbed sediments must be rich in nutrient since the pyramids (in this group anyway) were covered in a dense marine growth of soft corals (Acanthagorgia sp.,), algae, barnacles, bryozoans and small anemones (below). Stinging hydroids (right) were abundant. Like the huge offshore installations of the BSP, there was virtually no space left on the surfaces of the structures where the substrate was still visible.

The seabed in this location (west of the SW Ampa Field) is muddy and easily disturbed. The numerous holes must be occupied judging by the occasional ejection of clouds of sediment, however, we never observed their residents. A crayfish, covered in silt, was living in the typical scour under the base of the pyramid, and a cuttlefish hovered slightly above. Schools of cardinal fish (Apogon sp.,) and black spot snappers (Lutjanus sp.,) hovered on the edge of visibility making photography challenging. (A challenge that this photographer has yet to overcome)!

On every pyramid visited (the group of six lie within 20 metres of each other and are easily covered in one dive), the distribution of species seemed similar. Nudibranches were quite apparent. They are not something that the author normally notices, however, on this particular dive I saw four. Perhaps their colour, and the close-up concentration caused by the poor visibility, bought them to my attention.

Rising to the top of the pyramids, fishing lines and nets hung down. Schools of yellow tail jacks (Caranx sp.,) swirled around, at one point totally obscuring the view! Strangely and subtley, the sharp barrier between the clearer surface waters and the murky depths would rise up and down, sometimes revealing the schools of fish rushing around the six peaks, and then plunging the whole scene into the clouds once more. Alone on one of the peaks, swam a minute juvenile Bannerfish (Heniochus acuminatus). It was the only example we witnessed of a genuine reef fish. Would it last long in that environment, or would it soon become food for sometime larger? Who knows, however, the pyramids are alive and well, and supporting a thriving ecosystem.

On 1st May 2005, we visited a more northerly group of pyramids (1.3 n.miles north of the Southern Group).

The conditions excited and disappointed, as crystal-clear surface waters gave way to one metre visibility on the pyramids, with just the tops poking through the bottom silty layers.

In addition, the cluster of half a dozen structures had been pulled over recently, since much life was covered in silt and the muddy bottom of the legs is now exposed (right). This is no way to treat a developing ecosystem. Trawlers prowled the border half a kilometre away. Was it one of them that destroyed this habitat ? What nationality were they ?

On 8th October 2005, a training exercise was conducted using the pyramids (group 64) as a datum. It also provided the opportunity to observe any changes since our last visit on 28th February 2004, some 19 months ago.

The visibility was reasonable being about 6 metres near surface below a Baram layer of a few metres, gradually dropping to about three metres at the seabed in 15 metres. On both dives, more than six pyramids and one toppled and smashed one were counted. Sonar readings were also taken and a map constructed based on these readings, and the underwater observations. It was reckoned that seven vertical five metre pyramids were in the group with an eighth one collapsed. Two other sonar echoes were obtained but more than 40 metres from this group that were spread over a NE-SW trending line some 40 metres long and eight metres wide (sketch).

The diversity of fish life was advanced compared to 19 month ago, the species seen being noted below. The pyramids were still covered by a strong growth of Acanthagorgia sp., with a small amount of Dendronephthya sp. Stinging hydroids that had been plentiful were absent.

Of particular note were white whip corals (>) of about 20 - 40 cm in length. They covered the horizontal beams lying on the seabed and were not there 19 months ago. On both dives, small sea snakes (Kraits - Laticauda sp.,) were observed (40 cm).

Fish species were Hawkfish (Cirritichthys sp.,), an inflated small porcupine fish (looking nervous - Diodon sp.,) a very defensive grouper (50 cm - Epinephelus coioides >), a pair of Angelfishes (Pomacanthus annularis - common on the platforms), schools of Gold-saddle Rabbitfish (Siganus guttarus), Red(?) Snapper Lutjanus sp., and Sweetlips (Diagramma pictum).

21st April 2007: Excellent dive on the Pyramids

The pyramids are our 'bail-out' or training site that we use when the weather is too poor to reach Chearnley. On Saturday, limited to the afternoon only, we decided to dive on the southerly cluster of seven pyramids (7 miles WNW of the Fairway Buoy). The vis. was good enough at 10 metres to see the peaks of three or four of the cluster, but near the sea-bed the vis. dropped to less than a metre. A chilly layer of water also dissuaded divers from venturing to the bottom. For the second dive we moved to the northern cluster about a mile away and what a difference! We last dived this group on 1st May 2005 and found that the pyramids had been toppled (presumably by trawlers). Since then, the bare structures have been covered by soft corals Acanthagorgia and Dendronephthya. This has attracted colonies of rabbitfish and batfish (Platax teira), whilst the normal denizens of a well-established platform, pufferfish and hawkfish patrol the shadows. Jacks, rainbow runners and a school of large, yellow-tail barracuda swirled around in the gloom. One metre-long barracuda surprised us as it emerged from within the tangle of concrete pillars.

On top of one of the pyramids, an orange crab had attached a piece of acanthagorgia to its head as camouflage!

It seems that the secret of this cluster's success is the fact that it was toppled and has subsequently collapsed into a shady jumble of pillars that provide all the nooks and crannies essential to the formation of a marine eco-system.

On a less enthusiastic note, a box jellyfish (poss. Caribdea alata grandis) was spotted by Mark and Mark. Certainly it's the jelly time of year, so cover that exposed skin when diving!