Author: pablo madrigal

The last part of the monitoring program was monitoring bull sharks (Carcharhinus leucas)  in Cabo Pulmo National Park. This was very exciting for me due to the fact that Cabo Pulmo’s success as a Marine Protected National Park goes hand in hand with very strict diving regulations. So I was very excited for the opportunity to dive in this place. We learned that Cabo Pulmo is a IUCN category II (National Park) so it’s protected  for the ecosystem services it provides as well as for recreation. It is the oldest of three coral reefs in the west coast of North America, and it’s recovered 400% total biomass, so it’s one of the best examples in the world regarding conservation and citizen engagement from the local communities. It was heavily fished because there were very big game fish and it was poorly managed. As time went by, the population of top predators like sharks and marlin began to decline. Today, Cabo Pulmo is the only well-enforced no-take zone in the gulf.  This is truly an amazing example of what happens when communities put pressure on the government to create protected areas. There had been two proposed resort developments, both of which have been shut down. We were going to stay in a bungalow over night because we had two days on the itinerary:  on the first day we were going to perform a beach patrol and see if we managed to spot any sharks from shore, the second day involved three dives with the team. The data collected from the beach patrol would help a partner NGO (Pelagios Kakunjá) for the research they do in the area. In order to identify them from the shore, and during the dives, we learned a few things regarding shark morphology that we had to keep in mind when performing the searches. Bull sharks (Carcharhinus leucas)  have blunt rounded snouts, and they have a large, stocky shape, they have a large, triangular first dorsal fin, and dark ventral flip tips. Lemon sharks (Negaprion brevirostris) have a yellow to olive colour. The most particular thing we looked at, specially from shore, is that their first and second dorsal fins equal in size and shape.  Black tip sharks (Carcharhinus limbatus) have black tip fins, and a white anal fin. They are medium sized stocky sharks and have a long pointy snout. Tiger sharks (Galeocerdo cuvier) are very recognizable due to the pattern of stripes and dots that runs down their  backs. Their teeth are very distinct, they have a deep notch, are heavily serrated, and the lower and upper teeth are similar. White tip reef sharks (Triaenodon obesus)  are smaller in size and they are slender. Their eyes are horizontally oval, and have a down-slanted mouth that almost makes them appear grumpy. The white tips appear on the 1st dorsal and caudal fins. They have tricuspid teeth. Nurse sharks (Ginlgymostoma cirratum) are usually found at the bottom, they have tiny eyes, and they have nasal barbels. They have rounded fins, and their caudal fin has no lower caudal lobe for better navigation (With them being bottom dwellers, a lower lobe would keep making resistance with the sand). We spotted three juvenile lemon sharks during our beach patrols. On the second day we managed to see a beautifully large  pregnant female. I was in complete awe being in the presence of that animal but you could see she was scared of us in her evasive manner. I consider myself very lucky to have been able to see her even for a couple of seconds. Other than that encounter, we didn’t manage to see any other sharks. However, we managed to swim with a gigantic school of jacks.

 

 

The second module of the program included shark surveys off the coast of Cabo San Lucas. We were searching for pelagic species such as short fin makos (Isurus oxyrinchus), smooth hammerhead (Sphyrna zygaena), silky shark (Carcharhinus falciformis), and blue sharks (Prionace glauca). We had to record each encounter, take photos of any obvious markings for the photo ID, as well as record the behaviour of the shark towards the divers. We had two days scheduled for fieldwork in Cabo San Lucas and, unfortunately, on both days no sharks stayed long enough for the team to jump in the water with them. However, on the second day we spotted a smooth hammerhead. The shark diver leader preceded to start the chumming session and it was clear that the shark bit the bait, but didn’t stay long enough. The subject of chumming is a very controversial one and we received a series of very informative lectures prior to the field work days. We learned that there are two main ways to attract a shark: organic and inorganic. Organic provisioning would be the use of bait, like the head of a tuna and you would place a rope on the side of the boat and wait to get the attention of the shark. Chumming is often used in conjunction with baiting and it involves the use of oils or liquids, or fish body parts (sardines are often used because of their fatty properties). We also learned that some species don’t react the same to organic provisioning which is when inorganic provisioning occurs. Species like the mako sharks are very visual predators (large eyes), and they react to shiny or colourful preys. Therefore, items like plastic squids or fake seals would be most likely utilized. Very little is know about the effect of shark provisioning, and there is little to no research available on the subject. Part of the research done by The Shark Odyssey involves recording shark behaviour towards the bait, the chum, or the inorganic materials and building a records database to help determine if there are indeed behavioural changes.

Even though we didn’t have the opportunity to swim with sharks on this section of the program, I was not disappointed by any means. We learned a lot about conservation issues regarding shark populations, and we finished the day swimming with a massive school of mobula rays (Mobula munkiana) with hundreds of individuals. They were most likely mating since you could distinguish scars on the left side of some of them. They were also rows of mantas swimming and turning, most likely a female followed by males, as this is a mating behaviour observed in other species of mantas.

Today finalizes the Whale Shark module of the program. It has been unreal being face to face with these gentle giants. The first time I saw a whale shark I remember I couldn’t move and was just admiring the peacefulness of the animal. We were in charge of taking Photo ID’s of the side of the shark making sure we could show the white dots going from the gills to behind the first dorsal fin. This is because we would then submit those photos to a worldwide database that measures the distances from the dots and then identifies if the shark is a new sighting or of it’s been spotted on a previous encounter.  Another thing that we had to learn was measuring the shark with the use of a GoPro attached to a rig with two lasers on either side. This was particularly hard because sometimes conditions were not the best at sea and it was hard to locate the lasers while making sure the entire animal could fit into the shot. Another particularly important thing to remember was that we had to avoid pointing the laser at the eyes since this could cause damage. The third part of the monitoring included visual observations of any lacerations, amputations, or markings that we could identify that would help isolate the sharks in order to see if they were seen before or they were a new sighting. The season is almost over in La Paz bay and most of the sharks that aggregate here are male juveniles of around 7m in length  I am learning more and more of how important it is to be respectful of these creatures and to make sure we are taking steps, however small, into protecting them for future generations where they can thrive like they use to. 

 

Tomorrow we will have an entire day of exciting lectures where we will learn about shark biology, Cabo Pulmo National Park, and shark tourism and conservation. 

Today was a very productive day of learning about general shark knowledge. Most of the day was spent on lectures about whale shark (Rhincodon typus) biology, conservation status, and threats. We learned how to use lasers attached to a camera rig to estimate the size of the shark, as well as the code of conduct that one must follow when swimming with these gentle giants. A lot of their general behaviour still remains unknown, however, with the help of photo ID and general identification such as scars, amputations, and lacerations, one can identify specific individuals in a population. Following the lectures, we had a good time identifying the different types of jaws that ‘El Museo de la Ballena’ (The Whale Museum) has in storage in order to build a more concrete catalogue  for them to work with. The Shark Odyssey has many partners here in the sea of Cortez, and the whale museum is one of them. They  do very exciting work with Sea Shepard, and we’ve been learning a lot. Tomorrow will be our first day doing fieldwork and I’m excited to experience swimming with these incredible creatures.

  

As part of my directed studies I’ve decided to take part in ‘The Shark Odyssey’ This is a shark conservation volunteer program located in La Paz, Baja California Sur that consists of three modules: Whale sharks in La Paz bay, Bull Sharks in Cabo Pulmo National Park, and Pelagic sharks off the coast of Cabo San Lucas. Today was our first day and ,together with two other volunteers, we  had a brief introduction into the program as well as the biology of the ‘ Sea of Cortez’. This is an incredibly diverse marine ecosystem where you can find over 900 fish species, a huge diversity of shark species, as well as almost one third of all marine mammals. The main focus of this program is to develop long-term monitoring practices of shark populations in order to help with conservation efforts in the area. Needless to say, I am beyond excited to take part in this project and  I am hoping to learn a lot!

Tomorrow we will have a Whale Shark seminar that will prepare us for our fieldwork in the next couple of days.