The wind was strong, the conditions were rough, and the combination of the two stifled any attempts we made at fishing that afternoon. Even the commercial fishermen, who know this area intimately, came up empty-handed. And without the necessary fish, we couldn’t search for hammerheads, which have very specific dietary needs. As juveniles, hammerheads feed on deep-water fish like rockfish, and as they mature, they switch to squid. They migrate from coastal nurseries to deeper offshore waters, reaching adulthood at around 15 years old. To attract them, we needed fresh fish that matched their preferences perfectly.

But since fishing wasn’t an option, we opted for a boat ride to the sea lion rookery at Los Islotes, courtesy of our captain. Los Islotes, located in the northern part of Espíritu Santo National Park, a UNESCO World Heritage site, is renowned as the largest sea lion birthing site in the northern hemisphere. Typically, between 400 to 600 sea lions can be found here, and upon our arrival, it was estimated there were about 300. The Sea Lion Colony consists of two rocky islets jutting out of the sea. The conditions were a bit chaotic, I must admit. We witnessed territorial males barking, mothers birthing, and rocks splattered with blood from the newborn pups. But despite the tumultuous state of the ocean and its rowdy inhabitants, witnessing this dramatic scene at sunset was simply unforgettable.

After witnessing the sea lions, we made our way back to Isla Partida, which is separated from Isla Espíritu Santo by a narrow channel. Both islands, located in the Gulf of California, are UNESCO biospheres and were completely uninhabited during our stay. Our mission here was to tag the last remaining scalloped hammerheads in the area, working alongside Dr James Ketchum, a 35-year veteran in Mexican shark science and the founder of the nonprofit, Pelagios Kakunja.

Dr James Ketchum had dedicated his entire career to using science to enable best management practices for scalloped hammerheads from his home base in La Paz, Mexico. However, without the right fish, we couldn’t hook the hammerheads on the long hand lines we were using, so we had to resort to his plan-b. As sunset approached, our only option was for an early wake up call at 4:30am to go fishing for bait. If we were lucky and got some solid bites, we could proceed with the shark tagging. The good news was that early morning is prime feeding time for hammerheads, so all hope wasn’t lost yet.

Hammerheads used to be abundant in the Gulf of California. In the 70s and 80s, Dr Ketchum’s mentor and the legend of shark science in this region, Dr Peter Klimley, often saw schools of up to 500 scalloped hammerheads. The area where we were sitting was once described by Dr Klimley as a global hammerhead hotspot, where he uncovered unexpected truths about why hammerheads use this area. Even in the 90s, Dr Ketchum recalled seeing hundreds himself, making the tagging process much easier back then. They would dive down on a single breath hold and tag the sharks using nothing more than a spear.

According to the Ocean Conservancy, “within the hammerhead family, there are two genera: Sphyrna, which has eight species, and Eusphyrna, which has only one species.” So, it wasn’t just scalloped hammerheads found here – it was the great and smooth hammerheads too. Today, we’d be lucky to see one  or two hammerheads. As for great hammerheads, they are nearly extinct in this region and considered critically endangered globally by the IUCN Red List. Their dire state is due to the usual suspects: commercial fishing, bycatch, climate change and habitat loss. The IUCN reports that “more than 90% of great hammerheads die after being caught by fisheries, and their global population has declined by over 80% in the last 70 years.” 

The IUCN has categorised populations of the scalloped hammerhead, great hammerhead and scoophead as critically endangered (meaning, on the brink of extinction); four other hammerhead species as endangered and vulnerable (smooth, bonnethead, scalloped bonnethead) and two other hammerheads as threatened under the Endangered Species Act (ESA). Similar to the plight of the great hammerhead, scalloped hammerheads face significant threats due to the high demand for their fins, which are used in shark fin soup. This dish, a status symbol in China, Taiwan, and throughout Southeast Asia, has also seen growing popularity in Western countries. Alarmingly, the Animal Welfare Institute has highlighted the widespread availability of shark fins in the USA.

Shark finning involves the brutal practice of cutting off a shark’s fins while it is still alive, and then discarding the mutilated body back into the ocean. This inhumane act leaves sharks unable to swim, leading to death by blood loss, starvation, or predation. The harvested fins are dried and later used to prepare shark fin soup, often served with chicken or seafood broth and herbs. This dish, symbolising affluence, can cost up to $100 per bowl and is frequently served at weddings and banquets. The practice of shark finning results in the death of an estimated 73 million sharks annually.

So, when did things go from countless hammerhead sightings on any given dive, to almost none? According to Dr Ketchum, it was around 1998-1999 when the decline became rapid and far more noticeable. Today, the baseline is dramatically different. In the days of abundant sightings, these ‘vortexes’ of hammerheads were primarily large females ready for mating. Now, pregnant females are rarely seen here; instead, we mostly encounter juveniles that use the seamounts around the island as their key habitats, particularly a place called El Bajo of Espíritu Santo.

Earlier that day, when we arrived at Isla Partida, we set up at the ranger site. Although tourism has increased in the area over the years, this particular time of year was relatively quiet. We pitched our tents behind the fishing huts to shield them from the wind, which was strong enough to make us worry they might blow away. We were surrounded by old shark fishing gear, long since retired as the local community shifted to shark science, tourism, ranger work, and the commercial fishing of less endangered species. Nearby, pelicans roosted on the shore, baby puffer fish swam in the shallows, and oyster catchers with thin, long red beaks foraged for food. Gigantic native cacti dotted the red hills in the distance, standing tall against the turquoise, clear, and cold water. With no connectivity, we were completely cut off from our mainland realities. Our mission was singular: to catch, tag, and release hammerheads, all in the name of science.

The midday sun was blazing hot, and the only way to cool off was to swim. We snorkelled around the island, battling the strong current on the way out and effortlessly drifting back to camp. Cooling off in the ocean also served another more nefarious purpose – it also doubled as our bathroom, as there were no ‘facilities’ on the island. As we sat around the makeshift dinner table, Dr Ketchum and his associates shared stories of their time at sea, their experiences studying Baja’s sharks, and their hopes for the future. Dr Ketchum had seen a lot, both good and bad, during his career. Despite our different backgrounds, there was something relatable about James – perhaps it was his relentless pursuit of answers about the sea and his determination to stay positive amidst our changing world. 

We’re early risers, but Dr Ketchum’s team was up even earlier. By the time we emerged from our sand-covered tents at 4:30am, battered by the night’s strong winds, they were ready to go. The rangers were preparing three boats: one for the scientists, one for the fishermen to catch bait, and one for us to observe and dive in. The bait boat set off first, wasting no time. Meanwhile, James walked us through the tagging process, step by step.

First, we would deploy the long hand lines. These lines, baited and set out strategically, would hopefully hook the hammerheads. Catching the sharks was an intricate process, particularly given their sensitivity and the need for specific bait to attract them in the first place. For sharks measuring 1-2 metres, the protocol was to bring them onboard the boat. Larger sharks, however, remained in the water to ensure their safety and reduce stress. Once caught, the sharks were rolled upside down into a catatonic state called tonic immobility using tail and belly ropes, which helped them stay afloat during the tagging process.

The captain was to play a crucial role, keeping the shark’s head up and its mouth open to allow for proper water circulation, essential for the shark’s breathing. To minimise stress, the sharks’ eyes were covered, calming them for the tagging procedure. The tagging involved a minor surgical procedure to insert the tracker, a small acoustic transmitter. This precise operation was performed with care to ensure the shark’s health. Alongside tagging, DNA samples and blood work were collected to gather as much data as possible for ongoing research.

The entire process was time-sensitive. For smaller sharks, the procedure needed to be completed within approximately five minutes, while larger sharks required a bit more time to ensure everything was done correctly and efficiently. The tags were equipped with a variety of sensors, including those for depth, pH levels inside the shark’s belly, and temperature. These acoustic telemetry sensors provided valuable data on the sharks’ daily movements, connectivity with other areas, residency, and migratory patterns. 

The tags were designed with a cocoon that protected the internal organs of the shark. When the tag was inserted into the body cavity, it settled in without causing harm to the animal. The insertion process involved a small incision followed by a few stitches. It was vital not to cut too deep or make too large of an incision to avoid injuring the shark and prolonging the procedure. The size of the tags varied depending on the shark, and typically, the sharks needed to be over one meter long to accommodate the tags they used. These tags communicated with underwater receivers, like those found on El Bajo seamount, relaying the comprehensive data on shark activity in the region.

In addition to the internal tags, they also used tags that were attached to the dorsal fin and extended with an antenna above the water. These tags were suitable for species such as silkies, tigers, whale sharks, and of course, hammerheads. They provided real-time tracking data via satellite, staying on the shark for about five to six months until the battery died and the tag’s eventually detachment within a year. These kinds of tags were particularly useful for tracking sharks in the open ocean and to study their migratory patterns. 

On the other hand, the region was well-equipped with receivers that collected data from the acoustic transmitters to help understand their residency, seasonal movements and connectivity, and the team was known to collaborate with other scientific groups to share and access this information from acoustic transmitters. This collaborative effort enhanced their understanding of shark behaviour and migration, ultimately aiding in their conservation.

The conditions had to align perfectly in order to successfully tag hammerheads while we were out living on Isla Partida. But sadly for us, it wasn’t our time in the sun. We found not a single one. Surprised? Not really. After everything we’d digested about the hammerhead situation out here around Baja California Sur, this was unfortunate, but not out of the norm. We’d witnessed the issue in real time, leaving us wondering what it must’ve been like here once upon a time – using our imagination to paint a picture one could only dream of experiencing again one day. 

But James and his team had a mission beyond just tagging sharks – they were carrying forward the legacy of Dr Klimley with a grand vision. The data they were gathering from these tags was essential for their conservation efforts, providing scientific backing to advocate for a marine protected corridor for these sharks. Despite not catching hammerheads that day, we tagged nearly ten silky sharks, contributing valuable data to support the creation of the marine protected area (MPA) that would safeguard the shark highway corridor connecting Loreto, Espíritu Santo Island, and Cabo Pulmo – approximately 15,000 square kilometres. This crucial area is currently unprotected, making James’ work vital in showcasing that what remains is certainly worth conserving and what the team aims to help rebound.

Is it possible to restore the hammerhead population here? Yes. That’s what all this evergreen work is for. And after having the best science sleepover, in our sea-blown and tiny tents on that deserted desert island, we’re confident when we say that Dr Ketchum and his team won’t sleep until they’ve made even more strides.