The world’s best aquarium in the Sea of Cortez
The whale shark is swimming straight towards me. Its mouth is more than 1m wide and its body a shadowy torpedo stretching into the hazy green water behind. Just below the surface, the velvety skin catches the light and shows off a pattern of thousands of white spots, as if it has been decorated by a crazed paintball fanatic. Barely seeming to flex its high tail, the giant passes me without a flicker of acknowledgment. As I try hard to keep up, I measure its size in arm spans — about 8m, more than four times my body length. But the whale shark, the largest fish in the ocean, is a harmless behemoth.
Whale sharks migrate vast distances and make seasonal appearances but in the Sea of Cortez, off Mexico’s Baja Peninsula, they find it hard to leave. “Last year they stayed until late May and they were back again in July,” says James Curtiss, owner of the Cortez Club diving centre. “They may even be year-round residents.”
The Sea of Cortez has an almost legendary status among divers and marine naturalists. John Steinbeck wrote a book about his voyage here aboard a scientific collecting expedition in 1940, and Jacques Cousteau famously called it “the world’s aquarium”. The gulf is divided across 155,000sq km between a temperate zone (north of La Paz, the state capital of Baja California Sur) and a warm-water “Panamic” zone (southward to Cabo San Lucas, a resort city on the peninsula’s tip). The confrontation and subtle mixing of these two ecosystems partly accounts for its richness of about 900 fish species and 32 types of marine mammals that gather to feed and breed. Massive blooms of plankton mean that even elusive blue whales are seen, along with the gnarled humpbacks and grey whales that sound and breach in the bay.
This rich sea is in stark contrast to the forbidding desert at its edge. Driving north from the tourist hub of Cabo San Lucas, giant cardon cactuses stretch to the horizon where the mountains, Cordillera del Pacifico, cast a great blue shadow in the midday heat. On a walk through a small section of a gorge, cutting from east to west across the Baja Peninsula, I am guided by David Alba from Cabo Adventures. Warning me to stick to the path and not to pick up anything without checking with him, he explains Baja is home to 17 of Mexico’s 34 species of snakes, including the rare tree rattlesnake. Alba’s love for the desert is clear as he explains how the biggest cardon cactuses weigh 20,000kg and are more than 500 years old, and then shows me the sap from the cinerea bush used by indigenous people as sunblock. There is an abundance of wildlife in this arid wilderness, including birds, from vulture-like crested caracaras to horned owls and bright vermilion fly-catchers.
Even on dry land, however, there is no escaping the sea. On the broad Malecon, La Paz’s main promenade, there is a bronze statue of Cousteau clutching a diving mask and staring out to the watery horizon. Further along the esplanade are statues of manta rays, sea lions, whales and dolphins, even a giant clam containing a gleaming pearl. On land at least, little seems to have changed since my last visit 10 years ago. A few more statues have appeared on the Malecon, and at the edge of the bay there are a couple of new hotels. I hope it stays that way; in my experience, mass tourism damages marine habitats.
That is not to say that the Sea of Cortez has escaped the ravages of human activity. Decades of overfishing have unbalanced the ecosystem, taking top predators such as sharks and marlin out of the food chain and leading to a surge in other species. Before the 50s there were no sightings of Humboldt squid, ferocious creatures up to 2.5m long that hunt in packs and cannibalise vulnerable members of their own species; now there are about 20 million, preying on shrimp and other molluscs. In the 70s, hundreds of hammerhead sharks were often seen at El Bajo, a sea mount and dive site. These days, sightings are rare because gill-netting and other fishing methods have dramatically reduced their numbers.
According to Curtiss, however, there are reasons to be optimistic about the Sea of Cortez. “Sure, there has been overfishing in the past,” he concedes, “but the attitude of local people has changed a lot in the 23 years I’ve been here. Plans for big resorts here have been opposed. I employ ex-fishermen as dive guides and they understand the value of live sharks and manta rays compared to the short-term gains of catching and killing them.”
La Paz seems to be slowly waking up to selling its own charms and conserving its best assets. At Los Islotes — a jumble of rocks north of Isla Espiritu Santo, a protected island off La Paz — a colony of about 300 California sea lions is thriving, bucking the trend for the Sea of Cortez as a whole, where numbers have declined by 20 per cent over the past two decades. A few years ago, documentary makers found that the colony was feeding on deepwater fish that sea lions would not usually eat; they had adapted their habits to feed on species beyond the reach of commercial fishermen.
All this makes me apprehensive about what I’ll find out there, a decade on. My diving logbook reminds me of encounters with shoals of colourful fish at Espiritu Santo; of male sea lions at Los Islotes blowing bubbles underwater to warn me off their lair. Would they still be there? On a bright, clear morning, I take a boat from La Paz north towards the offshore islands. Javier Olichea, my skipper, has fished and dived these waters all his life. First he wants to show me two craggy outcrops festooned with seabirds. El Merito (Grouper Island) is a nesting spot for blue herons and ospreys, while the sheer sides of guanoencrusted La Gaviota are home to a large colony of bluefooted boobies. After a quick circuit, we speed across open water towards the large bulk of Isla Espiritu Santo, a nature reserve of russet sandstone cliffs, cactuses and deep, sheltered bays with shallows as clear as glass.
As we head around the coastline, Olichea points to a distant flash of spray and calls out a litany of fish names: yellowfin, manta, marlin. A repetitive shadow catches my eye and Olichea steers a little further out. It’s a large school of long-beaked common dolphins hunting unseen prey. There is nothing common about their appearance, however, distinguished by sleek two-toned flanks and elegant tapering tail flukes. Sixty, perhaps 80, dolphins fly across the surface, jumping, flipping and standing on their tails as they purposefully herd a shoal of silver fish. On the glittering surface of the deep blue, they are living expressions of vitality, energy and survival. At Los Islotes, we hear the reassuring bark of California sea lions. Young pups, golden-haired females and bullish defensive males lie in nooks and crannies sunning themselves after their fishing expeditions.
Slipping as quietly as possible into the water, I swim to within a short distance of the rocks. Almost immediately a young female sea lion joins me and passes within centimetres of my head. Heading down towards the rocky slabs 4m below the surface brings her close, investigating my own clumsy movements while she turns somersaults beside me at dizzying speed. All is well at Los Islotes.
The Sea of Cortez is also famed for its encounters with giant Pacific manta rays; like whale sharks, these are harmless plankton feeders. Olichea explains they are usually seen from August to November. The hammerheads at El Bajo are still there from November to January, he tells me, albeit in smaller numbers. I ask him about the mysterious and little-known vaquita porpoise, the world’s smallest cetacean, which lives north of La Paz and is critically endangered. He says he has only seen two and most conservationists believe there are fewer than 100 left. Mexico has recently embarked on a renewed effort to capture the illegal fishing boats blamed for killing the vaquita, which become entangled in the gill nets laid for the totoaba, a big fish with a swim bladder that fetches high prices as a Chinese medicine. Mexican president Enrique Pena Nieto has pledged patrol boats and a nofishing zone to try to save this porpoise, which is so shy it was only definitively identified in the 50s.
Close to the port of La Paz, we steer towards a sandbank known as El Magote. Olichea has promised we’ll see more whale sharks, and soon I am able to swim with five. Olichea warns me not to touch and disturb their feeding. In this shallower water, green with plankton, I can see less than 1m. The sharks take the tiny plankton with gaping mouths, filtering water through their enormous gills. Small eyes are mounted in telescopic sockets that retract at any sign of danger, reinforcing their vulnerability, despite their size. Their life cycle is still a mystery and it remains uncertain where they go to breed.
But that is part of the allure of so much marine life. Encounters like this bring a sense of privilege. I am swimming with the biggest fish in the sea. To know they are still coming here, along with all the other marine life we have seen in just one day, is greatly comforting.
Sixty, perhaps 80, dolphins fly across the surface, jumping, flipping, standing on their tails
Swimming with California sea lions in Sea of Cortez, above left; flying manta ray, below
Sea of Cortez, above; swimming with a whale shark, above right; and basking sea lions, right