The Flying Mobulas of the Sea of Cortez (cont'd)

SeaWatch is an environmental advocacy organization whose focus is the Sea of Cortez. Every year, members of the group travel from La Paz to Loreto, speaking with fishermen along the way. According to their most recent survey completed in 2001, “things are bad.” Overfishing has definitely taken its toll. According to SeaWatch, sportsfishermen in Parque Nacional Bahia de Loreto say that their business is off 40% to 50% from last year, and the consensus among commercial fisherman is that there are no fish left to catch. “The money they make with their catches can't even pay for the gas to catch them.”

Dr. Russell Nelson is a consultant for SeaWatch. He blames the overfishing on “the escalation of gear types.” Longlines, trawls, spearguns, nylon nets, and large-scale commercial operations have replaced the individual fishermen using a hand line. It has all been done, according to Dr. Nelson, with “little regard for future sustainability.” And it is by no means unique to the Sea of Cortez.

The fishing gear arms race is a global problem. Worldwide stocks of fish and shellfish have been plummeting as fishermen resort to more effective but increasingly inefficient ways of fishing. As for Lucio, he is competing against large-scale operations, which use equipment he cannot afford. More and more he and others like him must turn to other species, species like mobulas. And inevitably, they do so using inexpensive and easy-to-use drift nets. There are piles and piles of them on the beach. What does this mean for mobulas, a group of fish about which few ever heard, let alone seen?

Fourteen years ago, Dr. Notarbartolo di Sciara wrote that the stringy flesh of mobulids is “generally considered of little market value.” But, as other species of prized fish continue to decline, fishermen who have families to feed and bills to pay will catch that which remains. In the conflict between long-term sustainability and short-term sustenance, I don't think there's any question, which will come out ahead.

SeaWatch has said that the primary threat to the survival of mobulids continues to be accidental nettings. Though California banned drift nets in 1990 and the United Nations declared a 1992 moratorium on use of the nets on the open ocean, they continue to be used in the Sea of Cortez. Drift nets are particularly problematic—some would say diabolical—because they kill indiscriminately. Strung from buoys and left alone, they kill which creatures happen to swim into them, be they mobulas or sharks, turtles or tuna. Worse, sometimes the inexpensive nets are left untended. These “ghost nets” continue to kill long after their owner has forgotten about them.

Worldwide, bycatch accounts for 20 million tons a year of unwanted fish. About one-fourth of the world's catch is thrown back. The ratio is even higher among the take from shrimp trawlers. According to the Monterey Bay Aquarium's Seafood Watch Program, “Catching shrimp in trawl nets can kill up to 10 pounds of other animals, for each pound of shrimp.”

Dr. Villavicencio has the build of a lumberjack, but he is soft-spoken and has deep eyes. He tells me that the government gives fishermen permission to use a total of 50 drift nets for the catching of billfish and 200 drift nets to catch sharks. Add to these 250, mile-long nets, the hundreds of nets used without government sanction. “In Mexico,” as Lucio so aptly put it, “the law does not matter.” It is easy to see how such practices could affect the very viability of a species.

Unlike stingrays, which have spines or stingers in their tails, and most sharks, which have the option of biting would-be predators, mobulids have no defense mechanisms other than their speed and their size—all, that is except for Mobula japanica, which has a stinger. Dr. Nortarbartolo di Sciara writes that mobulids produce “a single huge pup presumably every 2 to 3 years.” Because of their slow rate of reproduction, mobulas and mantas (along with sea turtles, whales, and many sharks and sea birds) are especially vulnerable to stock depletion. John A. Musick writes in his article “Ecology and Conservation of Long-Lived Marine Animals,” that among these species, there is a “long lag time in population response to harvesting.” For such species, it may take decades to recover from excessive mortality.

Today, due in part to the work of SeaWatch, the Mexican government now imposes a $10,000 fine for those convicted of intentionally killing a Pacific Manta Ray. But then, shrimp trawling is also illegal, and I saw for my own eyes that the passage of a law was unable to stop at least one group of fishermen.

As gruesome as it may seem to some, the harpooning of mobulas and other large members of a given species may actually be the environmentally sound alternative of choice. Dr. Villavicencio certainly endorses it. The practice is better, he tells me, because “the fishermen focus specifically on the big fish of one species.” Even the more widespread use of hand lines wouldn't result in the kind of indiscriminate carnage inflicted by shrimp trawlers and drift nets.

It will be some time, if ever, before such measures can return the Sea of Cortez to its previous abundance, the kind described in John Steinbeck's 1940 memoir Log from the Sea of Cortez. It is a chronicle that speaks of a sea “ferocious with life.” “The pelagic rock-lobsters littered the ocean with red spots,” he writes. “There was food everywhere. Everything ate everything else with a furious exuberance.” Clearly, this description no longer applies.

Much of the work towards revitalizing this tropical gulf will require learning more about mobulas. The first thing Dr. Villavicencio told me when we met was that “When it comes to cubanas, there are more questions than answers.” Explaining with any degree of certainty the odd jumping behavior is just the beginning. So much remains unknown. For example, no one knows exactly where mobulas go in between being pups and mature adults; they are never seen, not in shrimp nets, not sunning, nowhere. It's almost as if they vanish. It is assumed that they go to a place Dr. Villavicencio calls “the deep zone,” but that is only speculation.

More significantly, the magnitude of commercial exploitation is, as of yet, still a mystery. Researchers can only guess how many mobulas are caught and how many are really killed. There are no real numbers on the scale of the damage. For that, serious research is called for. Dr. Villavicencio spoke optimistically of several studies underway. Some Mexican biologists are currently working to produce a proposal for fisheries management. Also, there's work being done to affix telemetry tags to various kinds of mobulids and monitor their movements. Such efforts, it is hoped, will ultimately serve the long-term prospects of mobulids in the Sea of Cortez.

Maybe one day soon, the Mexican government will ban drift nets. Dr. Villavicencio spoke of the possibility. So did one of the men working with Lucio's brother as we walked together along on the beach. He told me that he would take around tourists in his panga. Whether the statement was just for my benefit, I cannot say. The ban against drift nets, even if it is passed, will need to be effectively enforced. La mordida, Mexican slang for bribe—literally translated, “the bite”— is still a common practice. (While driving through La Paz, I myself was pulled over on a trumped-up traffic offense and given the chance to “pay on the spot.”)

Few people have ever seen a school of hundreds of mobulas moving underwater. I have heard it described as a choreographic marvel, the salt water thick with creatures too many to count, all of them opening and closing their wings at once. Black when they close, white when they open. Maybe one day soon, I'll see this. But I am on my kayak now, the sun is dipping below the horizon and I have run out of film. That night, we lie out wool blankets and sleep on sand almost cool to the touch. The lights of the nearest city, San Jose Del Cabo, are too far away to see.

We are warned not to read too deeply into the motives and emotions of organisms. Steinbeck knew of the caution; surely, he was at least considering it when he spoke of the “joyful survival” of sea life. “It almost seems as if they are excited,” he said of the crabs and starfish and urchins fighting to stay attached to the rocks as the waves beat against them again and again. Much about the mobula perplexes me, but most of all I find it strange that a creature whose continued existence remains in doubt could choose that moment to behave with such exuberance. Explain those exquisite belly flops how you will. I call it joyful survival.

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Michael Albert is a professional photgrapher.
Paul Albert is an academic librarian.