February 25th to March 4th was a great week for our research on the population ecology of the giant manta, Manta birostris in Bahía de Banderas, Mexico. We were able to register 17 new individuals into our Photo ID database. We got to Yelapa with the mission to place a total of 10 acoustic tags and two satellite tags on the elusive giant mantas swimming around the south coast of Bahía de Banderas. Weather conditions could not have been better, with constant sunlight and very good water visibility on most work days. This of course made searching for the mantas the easy part of the job. The hard part was getting the photographer and the tagger perfectly synchronized to avoid frightening the animal.
Manta with both, the satellite and acoustic, tags. Photo credit: Ramiro Gallardo.
The picture above shows the two types of tags, the place where they are located and the technique used by the diver. Usually we only put one tag in the right pectoral fin, but we put both types of tags in this organism to watch for differences in the data recorded.
Some individuals were very calm, allowing us to tag them and take pictures without any sign of stress. We even named one “El Compita” (“The Friend”) because it swam around us for over an hour, watching us with his curious eyes, perhaps waiting to be cleaned by one of us. Some of the mantas observed during our work week showed signs of injuries produced by fishing lines, nets and boats; one of them had a fishing line stuck on one of its cephalic lobes. Fortunately, it did not swim away until Ramiro Gallardo cut the line, setting the manta free.
Mantas sometimes get tangled in fishing nets; luckily the team successfully cut it lose. Photo credit: Ramiro Gallardo.
Another task we had to complete was to give maintenance to the acoustic receiver located at Los Arcos and which was deployed by our collaborators from the Pacific Manta Research Group. This sensor was out of batteries so after changing them the receiver was ready to record new data as the mantas swim by. With the receiver at Los Arcos sensor, we monitor mantas using a total of four acoustic sensors that operate from different parts of the bay capturing the signals emitted by the acoustic tags on the mantas. Regardless of the weather, time of day, or if the team is present or not, this system of receivers capture data 24 hours a day, 7 days a week and provides reliable and accurate data on the mobility giant mantas.
Map of Bahía de Banderas and its popular divin spots. Photo credit: Aldo Zavala.
We were also visited by 18 students studying to get their degree on EcoTourism at the Instituto Tecnológico de Bahía de Banderas, who listened attentively to Manta Project Director Josh Stewart, while he talked to them about the project objectives, the goals we have achieved so far, and how to approach giant mantas without stressing them. The students were able to witness the tagging and photo identification of a black manta and watched this big manta descend into the depths after being tagged. This is the first time ever the project has this kind of visitors and it was a great experience for the students and the team.
One of the mantas approaches team members as they prepare to place a tag. Photo credit: Iliana Fonseca
The results of the week were 11 acoustic tags and two satellite tags deployed. One manta has an acoustic tag, a satellite tag and was entered into the photo ID database! Temperature recording equipment was also deployed in the acoustic sensors located in Yelapa and Chimo, which will give us the oceanographic data required to relate the upwelling and temperature changes with the presence of mantas. The Manta team leaves Yelapa grateful and very happy for the results, and we will be anxiously waiting for the next opportunity to visit this beautiful place. Greetings to all!