November 10-19, 2020

Dr. Deni Ramirez Macias
Ultrasound Pregnant Whale Sharks and Manta Rays
$3500 per person, quad occupancy

About the Trip

Join the fantastic crew of the Quino El Guardian, world-renown whale shark researcher Dr. Dení Ramírez Macías, and her team as we attempt to ultrasound pregnant whale sharks and manta rays in the Archipielago of Revillagigedo!

The whale shark (Rhincodon typus) and the giant manta ray (Mobula birostris) are filter feeder elasmobranchs. In some countries, these species constitute a fishing resource, while in other countries, they are more valuable as an opportunity to attract tourism. Therefore, the sustainable exploitation of these species depends significantly on the knowledge of their populations. This knowledge is minimal.

Both species are especially vulnerable due to their biological characteristics as they are slow-growing, late to reach sexual maturity, and found in small populations. All of this is why the IUCN Red List recognizes these species for the Conservation of Nature.

In the Archipielago de Revillagigedo, we can find giant manta rays and whale sharks that enable Dr. Dení Ramírez Macías and her team to study these charismatic giants. Their studies have focused on demonstrating the presence of pregnant females in both species showing that this is a critical habitat for these elasmobranchs and requires a top priority for its conservation.

Our expedition will focus on obtaining an ultrasound in females of both species to corroborate that they are pregnant and to evaluate the degree of the embryonic development. This information will help to substantiate the theory that these waters are necessary for reproduction and to strengthen the protection of habitat for the conservation of the species. A second goal will be to place a satellite tag to see her movements.

Our goal is to use the regular itinerary for diving in Socorro, knowing that we will be open to using any opportunity that presents itself to ultrasound whale sharks and manta rays.

Deni will also be doing presentations throughout the trip. These presentations will include but not be limited to:


1. Following the Giants: Whale Sharks
2. Conservation Biology of the Whale Shark
3. The Giant Manta Rays from Revillagigedo
4. Ultrasound on Mobula Rays
5. I3S software for whale shark and giant manta ray photo identification

To book your space, email Susan at

In 2017, Deni was aboard Quino el Guardian and became the first person to successfully ultrasound a pregnant manta ray in the open ocean. 

Check out this video of Dr. Deni Ramirez Macias performing an ultrasound of a pregnant manta ray Isla de La Plata, Ecuador in August 2018.

This expedition was in collaboration with Marine Megafauna de Ecuador and her team.

Video by Erick Higuera