The extinction of sharks is leading to a general degradation of marine ecosystems. The oceanic islands of the Mexican Pacific, such as Revillagigedo, constitute a real refuge where these predators are still found in regular abundance. This archipelago forms an extremely important habitat for many predators and also has one of the richest shark island faunas in the Eastern Tropical Pacific, where up to five different species of sharks can be observed on a single dive.
THE ISLANDS OF REVILLAGIGEDO AND THEIR PROTECTION
This far away point can only be reached by boat, in this case the SOLMAR V, in a little more than 24 hours, unless you have a "plug" with the Mexican Navy to be brought by plane.
San Benedicto, Socorro, Roca Partida and Clarión, the four islands of "Revilla", universe of marine life, became fully protected at the end of 2017. On November 24, this archipelago was declared a "Marine National Park", becoming the largest region in North America -148,087 square kilometers- where fishing is banned.
Endemic marine birds nest in its islands and there are four species of marine turtles in danger of extinction. In addition, in its waters there is an important population of sharks (white tip reef sharks, silky, galapagueños, silver tips, whale, tigers and hammerheads, among others) and the famous and majestic giant manta rays. The area is also home to breeding humpback whales, as well as other marine mammals such as dolphins.
Socorro, the largest island, still shows the fumaroles of the still active volcano on Mount Everman. On this island there is an area, specifically a point, called Cape Pierce. The encounters with dolphins, turtles and especially with manta rays at the end of the dive, in the blue, are a spectacle.
Clarion is the second in size and the farthest from the islands. You must sail approximately 45 hours from Los Cabos, Baja California Sur, to get there. It has a great diversity of fauna and flora in its impressive lands.
The third of the group is San Benedicto Island, which presents a gray and rocky landscape due to the last eruption of its volcano, the Barcena, in 1952, which grants an impressive aspect to the sight. Undoubtedly, the most "powerful" dive of this island is the famous BOILER: a kind of square pyramid, with several steps, ranging from three meters to almost infinity. At this point, early in the morning, dozens of dolphins come to greet you, not to describe the incredible choreographies made by the mantas or the dozens of hammerheads that can be seen in another area called the canyon. And with a little luck, which we had, you can see in June the large schools of false killer whales (pilot whales) crossing very close to the island.
Finally, Roca Partida, the smallest, with just 94 meters long and 15 meters wide. This is undoubtedly the most majestic and impressive in terms of marine life in the middle of the Mexican Pacific. At the beginning of the dive, the island welcomes you with thousands and thousands of fish spread out in different schools, you can hardly see through them. On one of its sides, there are balconies full of whitetip reef sharks, which in mating season, come out by the dozens in search of a mate. Other sharks such as silky and silvertip sharks also inhabit Roca Partida, groups of up to 25 specimens were seen in almost every dive. The manta rays, which often pass close to the wall, are another attraction of the small island. And if you go between January and March, if you are lucky you can see humpbacks with their calves.
TAGGING SHARKS
During the nineties different species of sharks could be observed with regular abundance, however, in recent years the intense illegal fishing activity has seriously endangered the main shark refuge in Mexico. For this reason, immediate measures are being taken for their conservation.
Dr. Mauricio Hoyos and Pelagios Kakunjá are carrying out a telemetry study of sharks to determine movement patterns, inter-island connectivity and residence, as well as a program of shark censuses and genetics to estimate population size and structure, in order to know the behavior and ecology of these species, their status and population dynamics.
Para ello, se están usando marcas ultrasónicas, que emiten un código específico registrado por estaciones acústicas. Las marcas son colocadas externamente con una vara hawaiana para pesca deportiva durante una inmersión normal y de manera interna mediante su captura, haciendo una incisión en la cavidad intraperitoneal.
Las estaciones acústicas consisten en un receptor submarino tipo VR2W, que registra las señales emitidas por las marcas ultrasónicas en un rango de 300 m. Las estaciones son colocadas a profundidades entre 20 y 30 metros, en zonas de agregación de las diferentes especies en el archipiélago. Hasta el momento existen 14 estaciones acústicas en las cuatro islas del Archipiélago, pero la meta es colocar al menos 35 para tener una máxima cobertura. Hasta la fecha se han marcado unos 110 individuos de ocho diferentes especies, pero haría falta marcar más, con el fin de determinar cómo utilizan las islas del archipiélago y la importancia de la reserva para su conservación.
THE EXPERIENCE WITH MAURICIO HOYOS
On this occasion, Dr. Hoyos' objective was to tag female hammerhead sharks (Spyrna lewini). This would determine whether they travel from Revillagigedo to protected areas of the Sea of Cortés to give birth, and thus further protect that area from illegal fishing.
He was accompanied by the famous Mexican free diving champion, Alejandro Lemus. Hammerheads are very shy sharks, so trying to make the tagging in "apnea", in silence, was a consistent motive to achieve the objective.
In the end, the target could not be achieved. The hammers were far away and scarce. Mau's decision, already at Roca Partida, was to change the target shark. The new one was to tag at least one galapagueño female. During the first dives in this small island we were able to observe groups of 24 or 25 specimens of this species, especially a female that exceeded three meters.
Excitement was high. My mission was to take pictures of the tagging and the behavior of the shark afterwards. Mauricio mounted one of the acoustic tags on his Hawaiian and explained to me how we were going to proceed. The first thing was to find the Galapagos and then identify the female, not an easy task, as the sharks could move away from the island or go deeper than we could go down. If we found the target, Mau said, he would have to reach her quickly from above, so that she would not identify him, and then aim at the base of her dorsal fin, preferably on the left side, and shoot to leave the mark.
It really didn't look easy at all. When you approach a moving shark, it is not very easy to chase it, let alone be close enough to hit it with this kind of tagging technique.
It was said and done. Gear on and into the water. The search for "the female Galapagos shark" began. In a short time we saw the group, there were quite a few of them and among them a female, but it did not look like the biggest one. We went around some more, about 25 meters deep, to look for "the big one" but we were unsuccessful. Mauricio signaled me that we were going to mark the one that was a little smaller. We positioned ourselves, followed it, flapped our fins at full speed and when we were less than two meters away, the shark gave a powerful flap of its tail and escaped. What bad luck! But no, it was not so bad because after the lamentations between the two, Mau turned his head and there she was, the female, the biggest one. Once again we got into position, started flapping our fins as if the world was going to end and followed her for a few seconds. Dr. Hoyos accelerated the pace even more, I got right behind him, he reached her at a distance of just over a meter and... BANG, successful tagging. In this case, because the wall was very close to his left side, it was on the right, but in the end, it was marked.
The shark jumped and swam quickly out of our reach, although in a few seconds it returned to where we were as if to reproach us for what we had done. It circled among us several times, calmed down, we observed it perfectly and it calmly disappeared into the blue, marked with an acoustic signal that will give information to science to protect them even more.
