“No we do not catch hammerhead sharks here anymore. The big sharks, they are all gone.”
“No, ya no capturamos grandes tiburones martillo aqui. Todos se han ido.” Javier, a fisherman from a remote fishing village 3 hours north of La Paz Baja Sur tells us.
We are on an exploratory expedition in the Gulf of California, visiting islands and searching for hammerhead sharks. With a team from Pelagios Kakunjá, a non-profit based in La Paz Baja California Sur Mexico, we are interviewing and filming fishermen and other stakeholders to discover their perspective on sharks, fishing and ecotourism.
Scalloped hammerhead sharks have disappeared from most of the Gulf and especially around the underwater seamounts in the southwestern Gulf of California. On a 2-week voyage of discovery covering 250 miles, we are following up on a recent scientific study published by our team members with Pelagios Kakunjá documenting that hammerhead sharks, once common in the Gulf, are now nearly absent. The abundance of these sharks has been reduced significantly at the once famous dive destinations el Bajo and las Animas off the coast of Baja California Sur. Researchers from Pelagios Kakunjá collected observations from divers over the last 50 years and found that scalloped hammerhead sharks (Sphyrna lewini) have been reduced by 97-100% at the two seamounts where they were most common.
“Puerto Escondido station was one of the richest we visited, for it combined many kinds of environment in a very small area; sand bottom, stone shore, boulders, broken rock, coral, still, warm, shallow places, and racing tide.”
John Steinbeck Log from the Sea of Cortez
On their 1939 expedition documenting marine life in the Sea of Cortez (also called the Gulf of California), later published in their journal Log From the Sea of Cortez, John Steinbeck and naturalist Ed Ricketts describe the richness of – mostly undocumented to western science- marine life in the intertidal and near subtidal marine zones. They describe large sharks, mantas and other marine life in abundance, and Puerto Escondido as so rich they could have stayed for a month, but had to move on. Steinbeck and Ricketts also describe the abundance of marine megafauna, including scalloped hammerhead sharks, that once inhabited the Sea of Cortez in large numbers.
Once a rich mangrove and tidal wetland, dredging and the development of a marina in the estuary has impacted habitat, including an important nursey site for scalloped hammerhead sharks. However, on an expedition over 80 years later, Duke and Stanford University marine ecologists re-created the journey of Steinbeck/Ricketts and recorded a dramatic difference in the assemblages and abundance of marine animals. The team reported seeing almost no sharks as they revisited the collecting sites first explored by Steinbeck and Ricketts.
“Diversity and abundance of large gastropod snails and echinoderms (sea stars, sea cucumbers and relatives) have declined at many intertidal sites and large pelagic species of tuna, sharks, billfish, and turtles are also much less abundant” Sagarin et al, 2008
On our voyage, we were to experience the same when it came to sharks. Coastal development and pollution, fishing, disease and climate change may all be drivers of the observed change in species, Sangarin opined. A targeted commercial fishing effort and the shark fin trade are to blame for the decline of sharks in the Sea of Cortez.
Protecting the Hammerhead Highway
Using acoustic and satellite tags the team has demonstrated that the seamounts and submerged ridges provide important habitat, and a migratory highway, for scalloped hammerhead sharks. Other species of importance in the area between the eastern Cape and the southern islands include whale sharks, great hammerhead sharks, grey whales, green sea turtles, endemic mobula rays and other large fish.
Dr. James Ketchum, leader of Pelagios Kakunja and his team have also discovered areas where hammerhead sharks are pupping, and with the help from local fishermen, the team is tagging and tracking juvenile sharks. To allow hammerhead sharks to recover, shark fishing must be eliminated along the pathway between the nursery areas and the feeding areas along which the shark migrate. Along this proposed protected zone we are building relationships and gathered information from local fishermen to support this new MPA. Along the way, we we searched for sharks.
Visiting many of the same locations Steinbeck and Ricketts first described, we saw few large fish at most of the areas, including islands 30 miles from the coast.
At on spot during our survey up the Gulf we dived a reef with schools of graybar grunts, yellowtail surgeonfish and large clusters of healthy acroporid coral at El Pardito, an isolated fishing village located on a rock near Isla San Franciscito. Protected by the local fishermen, primarily from the Cuevas family, we saw large fish like bumphead, bicolor, and blue chin parrotfish, fish rarely seen outside areas with immediate stakeholder protection like this. By providing services to scientists, students and tourists the fishing community could receive economic benefit, and the protected reef would flourish. It might even attract sharks back to the protected area.
Our visit to the remote Las Animas revealed abundant reef fish like sergeant majors, angel fish, and goat fish, but not a single shark. Other predators were present however. California sea lions are abundant, ambushing us and gamboling in front of the camera. The island also has a small population of Guadalupe fur seals. A large pod of bottle-nosed dolphins swam past as we searched for scalloped hammerheads, but after searching around Las Animas, we left disappointed by the absence of sharks.
In other areas in Mexico, sharks have returned to marine protected areas such as the Revillagigedo Archipelago, a World Heritage Site located in Mexican waters 240 Km west of Cabo San Lucas. Rich with fish and other marine megafauna like whales, the islands are a major attraction to SCUBA divers, especially for those who wish to experience sharks. Over 1 million dollars USD per year is generated by dive tourists who seek schools of hammerhead sharks, whale sharks, manta rays and other sharks at this site alone. Of divers surveyed in a study on the value of dive tourism, 23% identified sharks as the reason they wished to visit the Revillagigedos.
On the tip of the Baja Peninsula, Cabo Pulmo is a protected area located between Cabo San Lucas and La Paz. Established in 1995, this marine protected area covers 27.5 square miles of the Cabo Pulmo reef. This park has become a dive tourism destination with recovered populations of bull sharks and reef sharks. With occasional visits by adult hammerhead sharks, the MPA also has the healthiest most intact coral reef along the Baja Peninsula.
After 17 years of marine protection, Cabo Pulmo became the healthiest marine reserves in Baja. A 2-year study conducted by Scripps institute from the university of San Diego revealed that the number of fishes or biomass in the ecosystem of the park increased more than 460% between 1999 to 2009. The MPA has been a financial success for the former fishermen village turned tour operators. However, the sharks and other migratory fish do not enjoy protection when leaving the cape for areas outside the protected zone.
Like other species of large shark, scalloped hammerhead sharks, are more vulnerable to extinction than most marine vertebrates. With late onset of reproductive maturity, these sharks produce few offspring, have long gestation periods and are slow growing, making them vulnerable to overfishing. As has been experienced, their schooling behavior, migration through open waters and aggregation at pinnacles make these sharks highly vulnerable to targeted fishng. According to the IUCN Red List of Threatened Species, scalloped hammerhead sharks are critically endangered globally. The sharks are coveted for their large fins, which are used in shark fin soup.
On a positive note, while returning to La Paz we were greeted by two whale sharks feeding outside the harbor. One of the few protected species of sharks, whale shark tourism is a flourishing industry at La Paz and near the Cape.
Shark Stewards has joined Pelgios Kakunja to develop a protected migratory swim-way that connects critical nursery and aggregation areas like Las Animas along the eastern peninsula. We are also working with local communities and artisanal shark fishermen to develop sustainable ecotourism between Cabo Pulmo and Loreto to support a no-fishing zone, and allow endangered hammerhead sharks to recover.
Steinbeck, John, 1902-1968. The Log from the Sea of Cortez : the Narrative Portion of the Book, Sea of Cortez, by John Steinbeck and E.F. Ricketts, 1941, Here Reissued with a Profile “About Ed Ricketts”. New York, N.Y. :Penguin Books, 1986.
Sagarin, Raphael & William, Gilly & Baxter, Charles & Burnett, Nancy & Christensen, Jon. (2008). Remembering the Gulf: Changes to the marine communities of the Sea of Cortez since the Steinbeck and Ricketts expedition of 1940. Frontiers in Ecology and the Environment. 6. 372-379. 10.1890/070067.