In Pursuit of Hammerheads

Aug 2001, by Simon Rogerson DIVE
Cocos Island and Malpelo are two of the wildest and most isolated dive sites in the world. Simon Rogerson joined a trip that aimed to explore both islands on a single, ambitious charter

If such a thing as slack tide ever existed at Malpelo Island, we had definitely missed it. Fists clenched around the anchor line, the current ripped at us as we dragged ourselves down through a layer of green water. Somewhere below was an unexplored sea mount: no one had ever been there before, and I was rapidly finding out why. Malpelo – a remote and inhospitable hunk of rock in the eastern Pacific – is famed for its challenging diving conditions, and this was a suitably violent baptism.

At the surface it was a balmy 28ºC, but at 9m the water danced before my eyes as a cooler current enveloped me. Scalloped hammerhead sharks turned and wheeled, flickering shadows at the limits of visibility. At 26m, a second thermocline kicked in, cruelly lowering the temperature to 15ºC. Here, beneath the upper layers of soupy bath water, it was exceptionally clear, but dark, like cave water. I looked across the expanse of the sea mount, at fellow divers dragging themselves over the current-blasted rock, their bubbles twisting behind them in agitated patterns.

I hauled myself to the drop-off and peered into the void. Malpelo is probably best known for its schools of scalloped hammerhead sharks, which tend to cruise the upper thermoclines at 8–12m. But in this deeper, cooler water, other predators reign. Squeezing into the shelter of a crevice, I heard what sounded like distant thunder, and looked up to see a pack of monstrous almaco jacks swooping close around my head. They were really pleased to see me.

I have witnessed curious behaviour in predatory fish, but nothing as bold as that being displayed by these almacos (more than a metre long, they were far larger than textbooks suggest – everything is bigger than it should be at Malpelo). They seemed to want to brush their bodies against my scuba equipment.

I was being used as a back-scratcher, so I did what any self-respecting diver would do in the circumstances: I tried to take a photograph. Past experience has shown that the simple action of putting an eye to the viewfinder is sufficient to send most fish packing: entire schools have fled the vicinity before my hand has so much as twitched towards the aperture control. But the almacos (see photograph, right) were unperturbed, and continued to circle at high speed, refusing to flinch even as the powerful flashgun fired directly in their expressionless faces. Annoyingly, the diver in front of me was using a rebreather (the manufacturer of which claims it will get you closer to nature), but the fish weren’t dive-bombing him.

Surfacing from any dive at Malpelo, the barren immensity of the island looms large. Actually, it seems misleading to refer to Malpelo as an island, when it’s simply a very big rock. However, the Colombian government has gone to some lengths to get it legally recognized as an island, to secure territorial rights to the surrounding waters. To back up its claim, they keep a permanent Navy presence on the rock.

There is absolutely nowhere to land a boat of any size. When supplies are landed, vessels must draw up beneath a crane that is suspended from the rock face. A rope ladder is then thrown to the deck. For the visitor, Malpelo doesn’t offer many topside attractions. There are birds, and views of the Pacific. Otherwise, the Colombians hole up in their quarters – perched on one of the rock’s level sections – and wait to be relieved. I only hope they have satellite television.
For divers, Malpelo is an altogether more adventurous prospect. The rock was born from the same volcanic hot spot that gave birth to Cocos Island and the Galápagos archipelago. Malpelo is approximately four million years old, Cocos a sprightly 2.5 million and the Galápagos a relative whippersnapper, spewed out a mere million years ago. Like the other two, Malpelo attracts pelagic fish in great numbers.

I was on board the liveaboard Sea Hunter which was on one of its occasional charters that visit both Malpelo and Cocos Island. Running a diving operation at Malpelo is fraught with difficulties. There’s no sheltered anchorage, so the skipper has to choose the most protected side of the island (north, in our case), and lay anchor close to the cliff face. Crew members take it in turns to keep watch through the night, in case the ship drifts too close.

In the water, divers are treated to a concentration of schooling hammerheads possibly even greater than at Cocos Island. The crew thinks this may be due to the fact that Malpelo is smaller than Cocos, so you see the same schools again and again. Unlike other tropical shark sites, the hammerheads are typically seen in the shallows, where the warm surface water meets the first of the thermoclines.

Malpelo owes the complexity and richness of its ecosystem to the many ocean currents and counter-currents that converge there. Of these, the Peru Coastal or Humboldt current is probably the most important, bringing a bounty of nutrient-rich water. It is also quite chilly. Choosing the right wetsuit is a practical impossibility at Malpelo: a 5mm steamer may appear to offer too much insulation at the surface, but by the time you’re hunting for ugly/beautiful critters such as the rosy-lipped batfish at 40m, you’ll wish you had a 7mm or even a drysuit. Hoods and gloves are essential.

Most of our dives were carried out over a stretch of coast on Malpelo’s north side, which carries fitting site names such as The Freezer, The Fridge and Freezer Wall. We saw hammerheads on pretty much all of our dives here, but visibility in the surface waters was uniformly poor, averaging 10–12m. The sharks simply weren’t seen in the cold, clear water below, although looking down, we occasionally saw sand tiger sharks lurking at 70m. There’s a lot of debate about these giant sharks: could they be a new, distinct species? Received wisdom now has it that they are a hitherto unknown population of small-toothed sand tiger sharks, also found in the Med.

There are some hefty swells at Malpelo, and several of our group were thrust on to the ubiquitous sea urchins when they failed to take its unrelenting force into account. Finding space to settle can be a challenge in itself, as much of the real estate is taken up by moray eels. The eels are the first thing you notice about Malpelo: they are everywhere, sneering from their lairs and undulating over the reefs.

Two American photojournalists on board the Sea Hunter – husband and wife team Stuart and Michele Westmorland – were especially prone to bumps and scratches when distracted by their work. Michele even received a warning nip from a moray (a nasty scratch, through several layers of neoprene), after accidentally settling over its home, but nothing could have prepared them for the unholy experience that awaited them at a site known as the Cathedral. This cavern is the Hong Kong of eel cities: scores of fanged faces leer at visiting divers, mouths agape in early-stage threat postures (some eel species, such as the jewel moray, open their mouths to breathe, but the Sea Hunter’s guides believe the speckled morays of Malpelo use the gesture as a threat).

An incredibly sudden combination of current and swell trapped the photographers in the cave and bashed them repeatedly against the walls, washing-machine style. Stuart lost an expensive flashgun, a fin and a bootee in the maelstrom (and another diver lost a reel trying to rescue him), but in the end was unceremoniously spat out. He was bruised and cut, but otherwise well. The eels must have known what was going to happen: there wasn’t one to be seen inside the cave.

Despite this mishap, it would be misleading to describe Malpelo as a destination suitable only for hard-core adventurers. An Austrian woman in my group had just 30 dives to her name, but seemed quite happy in the swell. Conditions change quickly and radically in the Eastern Pacific: the charter after mine had a very easy time at Malpelo. The truth is that anyone with reasonable experience and the sense to dive conservatively can have an enjoyable time here.

While Malpelo provides a range of unique sights and adventure dives, Cocos Island allows a similar experience, with radically better visibility. Certainly, the 30-hour voyage between the two gives divers a much-needed rest – a time to prod at urchin wounds, overhaul cameras and enjoy the Sea Hunter’s agreeably lowbrow video library.
Having enjoyed the adrenalin diving at Malpelo (which translates, inexplicably, as ‘bad hair’ – perhaps they meant ‘hair-raising’), Cocos Island offered a chance to see similar wildlife in easier circumstances. Conditions at Cocos are primarily determined by the North Equatorial counter-current, which carries warm water from the western Pacific to Cocos, making it a site in which it’s comfortable to wear a 5mm wetsuit. My visit took place in April, at the tail end of the dry season, when currents tend to be less severe, visibility is typically 25–30m and light can easily penetrate down to the sea mounts. Many prefer to visit in the rainy season when currents are more boisterous, but the hammerhead schools are seen more frequently and at more sites.

More nonsense is spoken about Cocos than just about any other dive destination, so here’s some fact. Designated a national park by the Costa Rican government in 1978, the 24 sq km island lies 600km south of the mainland port of Puntarenas, and 630km northeast of the Galápagos Islands. Cocos lies within the doldrums, an area of weak and variable winds where trade winds converge, forming the clouds which normally shroud the island’s 636m summit, Cerro Iglesias. Cocos receives a staggering 7m of rainfall every year, which in turn supports a very lush cloud forest. The excess water then drains off the island and into the sea via spectacular waterfalls, one of which was used for an early scene in the classic Spielberg film, Jurassic Park.

Cocos was discovered by the Spanish seafarer Joan Cabezas in 1526, and was shown as Isla de Coco in a map of the world drawn up in 1556. In the 17th and 18th centuries, it served as a hideaway for the pirates and privateers who flourished along the Pacific coasts of Spanish America. Several treasures are supposed to be buried here, including the legendary Lima booty, which supposedly consists of two tonnes of gold bars and sheets of gold that once covered the domes of churches. So far, some 500 expeditions have failed to recover any treasure.

The real treasure, of course, lies in the surrounding waters. Although the eastern Pacific cannot match Southeast Asia for marine biodiversity, Cocos boasts fish populations that pretty much put every other dive destination in the shade. The basis of the menu for larger predators is the ubiquitous Pacific creolefish, which is to Cocos what anthias are to the Red Sea. They certainly get a hard time from the island’s huge population of white-tip reef sharks The white-tips are normally sluggish by day, cruising the pinnacles or resting on sandy bottoms until dark, when they zip over the reef like heat-seeking missiles, hunting the creolefish. Evidently, they are also partial to octopus: quite a few sharks carry wounds on their gill slits, where a desperate cephalopod has tried to escape in the process of being devoured. It’s worth keeping a close eye on the white-tips – if they seem to be massing during the day, there’s a chance that a female has come into season, and any divers fortunate enough to be in the right place at the right time may witness their brutal courtship.

At Cocos, the ‘right place’ often turns out to be a sea mount named Alcyone (after Cousteau’s ship). Located off the exposed southeastern point, it is a classic site. On my first dive there, the sea mount had been clearly visible from the surface. I swam down the anchor line and paused at the bottom to collect myself before trying to find a suitable vantage point from which to look out for scalloped hammerheads. The idea is to wait by a group of barberfish, and wait for a hammerhead to approach in the hope of having parasites pecked from its body. This is the best way to get close to the skittish sharks.

I finned towards a raised ridge on the far side of the sea mount, which faced the current and was ideally suited to hammerhead-watching. Peering ahead, I was disconcerted to see another ridge that appeared to be moving beyond it. It took a while before I realized I was looking at a whale shark. She was a female, slow moving and untroubled by the clamouring mass of divers which now converged on her. Over the course of the next 35 minutes (every diver on our charter used nitrox 32 for the first two dives of the day, switching to EAN 36 for the third and fourth), she treated us to four similarly graceful passes, and was at the anchor line as we reluctantly started the ascent, gas levels predictably low.

The sea mounts and pinnacle sites off Cocos provide a good chance of witnessing animal behaviour. Divers regularly come across excitable swarms of leather bass and marbled stingrays, all of whom appear fixated by a particular patch of rock. In fact, they are trying to flush out juvenile cardinalfish, which hide between the spines of sea urchins. The predators converge on the urchins, some trying to use suction to pull the fish into their maws (you can hear the gulping sound), while others hope the prey will flee towards them in the confusion. The jacks in particular seem to inspire terror in fish of all sizes. And, they are devious brutes: on several occasions, I noticed a solitary island jack swimming under the voluminous folds of a marble ray. Whenever the sluggish ray passed by a suitable prey item, the jack would break from its cover and make a swift, darting attack.

At Alcyone, a pack of bluefin trevally streaming over the reef produces a deep, roaring sound that makes the sensitive hammerheads wince. Yet the sea mount remains the hub of hammerhead activity during the day. Invisible magnetic valleys and ridges radiate from Alcyone like spokes from a wheel. Following these ‘roads’, the hammerheads travel to distant feeding grounds to hunt squid, then return to their home base at dawn. On a typical dive at Alcyone, you can expect to see at least five or six schools passing by, with each ‘flyby’ typically lasting between 45 seconds and a minute.

On a few occasions, desperately trying to control my breathing, I was able to observe some extraordinary behaviour among the sharks. The centre of the schools seems to be occupied by dominant females, who intimidate their smaller sisters with acrobatic displays. The most spectacular of these was first identified by the biologist Peter Klimley, who called it the ‘corkscrew display’. It’s an astonishing sight: a 3m-hammerhead performs a reverse somersault while rotating her torso, producing flashes of light off her white belly. Large females have also been seen striking rivals with the undersides of their jaws, and bouts of rapid acceleration are common. The schools are composed exclusively of female sharks, but Klimley has observed lone males dashing into the central cluster of big females, performing torso thrusts to advertise their virility. If the male is accepted, the couple will leave the school and mate at the bottom.

Despite such insights into the private lives of super-predators, there remains much to be discovered at Cocos. To an extent, the island’s isolation affords natural protection, but an increasing number of fishermen are making the crossing from Costa Rica to defy the park wardens in their hunt for shark fins. Time and again – and despite confiscations of cargo – the same boats are stopped and searched.

It’s tempting to look at the issue from the point of view of the fishermen. After all, Cocos wasn’t put there for the exclusive pleasure of well-heeled tourists, and there are mouths to be fed. But the argument for unbridled exploitation doesn’t hold water. As a nation, Costa Rica has prospered through the preservation its forests and coasts. Ecotourism is the single most important earner of foreign currency – it brings in $59.4 million every month, and the figure is still rising sharply each year. The country has learned to be wary of short-term temptations that could lead to the long-term degradation of such a resource.

In 1997, the United Nations declared Cocos a World Heritage Site, after tireless lobbying by the late park director, Joaquim Garcia. Today, the island is depicted on Costa Rica’s 2,000 colones banknote. The reverse side of the note features a drawing of a hammerhead shark. Thanks to the banknote, the shark’s unearthly features have, to an extent, become synonymous with the economic stability that the country currently enjoys. The shark as a symbol of hope and prosperity? Now that’s progress.

Sea Hunter
MV Sea Hunter is the only liveaboard that visits Cocos and Malpelo in a single charter. Equipped with two 700hp engines, the Sea Hunter combines the large working platform of a functional boat with the air-conditioned luxury of a modern yacht. The boat takes a maximum of 18 passengers. For diving, they are split into two teams, each with a fibreglass chase boat and their own guide.
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