Searching for Whale Sharks in the Sea of Cortez

May 19th I boarded a plane for La Paz, Mexico and began an adventure of a life time. Thanks to a grant sponsored by the Seefurth Field School for Teachers, I would be spending the next seven days and nights in the Sea of Cortez (Gulf of California) aboard the 80ft. Don Jose in search of the elusive whale shark.

El Don Jose, home sweet home for the week. My cabin was on the upper deck.

There were nine other citizen scientists on board as well as five crew members, one dive master, and marine biologist Deni Rameriz.  The first night aboard El Don Jose, Deni gave us an introductory lesson on the natural history of whale sharks and whale shark research. Deni has been studying whale sharks for over ten years and is interested in learning more about whale shark population genetics around the world.

Marine Biologist Deni Ramirez.

Whale sharks migrate to the Sea of Cortez to feed and give birth. These enormous filter feeding giants feed on the plankton rich waters present in the Sea of Cortez. In order to study whale shark populations individuals need to be tagged and identified. Each shark is identified with photos of the lateral markings behind the five gills slits on the left side of the fish. The pattern of spots is used as a “fingerprint” which is unique for each individual shark and does not change over time. Our main responsibility was to try to get this shot or as we called it, “the money shot”. We all thought – no problem- we have our water proof cameras- if we are lucky enough to see a whale shark then we’ll take pictures and Deni will have the opportunity to collect the measurements and DNA sample that is critical to her research.

On our first morning a spotter plane was used to help locate whale sharks. After a half hour the call came that the pilot had spotted a whale shark. We could not believe our ears, we scurried to collect our snorkel gear and cameras and wait for the order to board the pangas.  (The Mexican government is very protective of whale sharks and scuba diving near whale sharks and touching the sharks are not allowed) With our gear in hand we boarded three pangas and began the chase. The pangas are small boats similar to row boats with small engines and can travel quicker and quieter than the Don Jose. The crew tries to position the pangas ahead of the whale shark so we can try to enter the water before the whale shark  approaches. It is hard to describe the adrenaline that flows through your body as you wait for the words to “get in”, however it is nothing compared to the utter sense of awe as you stand suspended in the water column and watch this gentle giant glide by you.

Meet Estella- an amazing fish. Sharing the same space with this incredible animal deepened my sense of wonder for our watery world. As she swam by our shared realm I could not help but be in awe of this gigantic creature even if it was for only a brief moment in time.

After being star struck you remember what your job is and begin swimming as quickly as you can in order to catch up to the shark and take a few photos.
I was amazed how fast and graceful this fish was. I gave up any attempt of getting the “money shot” I just wanted to be able to spend more time in the water with the shark. Once we realized the whale shark was out of reach we quickly pulled ourselves back into the  pangas and began the process again. We were able to get in the water with the shark two more times and Deni was able to measure the size of her mouth and tail however she was not successful in tagging her or obtaining the DNA sample. Deni estimated the shark was around 10 meters or approximately 30 feet. None of us were able to get the “money” shot of the markings by her left pectoral fin however Deni was able to get a shot of her belly which showed that we were following a pregnant female!

Swollen belly of a pregnant female.

We were amazed how fast the shark was moving. Whale sharks are very streamlined and are capable of swimming 3-4 miles/hour. That may not sound like a lot but it is much faster than most people can swim. Besides trying to  keep up we were also being very mindful of not getting to close  to the shark. You certainly don’t want to be in the path of an animal traveling that fast nor do you want to be to close to their enormous 6-8 ft. tail as it propels them through the water. One swoop of the tail could deliver a tremendous blow! Even though Deni was not able to collect all the data she needed for her research we all knew we had experienced something very special. Deni told us we could name the  whale shark and we all felt privileged to do so. As we sat out under the star filled night and reminisced about the spectacular day we shared we agreed Estella was a suitable name for our new friend. Estella means star in Spanish and she certainly gave us a stellar experience!

Thank you Estella for an amazing experience!

Like sharks everywhere, these animals are threatened worldwide, and Deni’s research contributes to the knowledge base necessary for their preservation.

For more information about whale sharks and Deni Ramirez and her research:

At the end of the trip Deni gave all her “assistants” a gift of a whale shark adoption from her program I choose Tikitiki to adopt in honor of all the CPS elementary school students.

Tikitiki-adopted for the elementary students of CPS

Mote Marine Laboratory has posted several photos and descriptions of researchers tagging whale sharks off of Cancun, Mexico.

“Aquarium of the World”


Jacques Cousteau called the Sea of Cortez the “aquarium of the world” because of the large number of indigenous (native) marine animals found there, and it truly is. Even though we only saw one whale shark, everyday we were surrounded by the beauty and bounty of the Sea of Cortez.  I was able to log 9 scuba dives, including one night dive and swam with moray eels, electric stingrays, tons of fish, and even sea lions- another once in a life time experience!

California sea lions

Espiritu Santos

Night dive in the arch

Read more about the aquarium of the world.

Click hear to see more pictures of the Sea Of Cortez

I am forever grateful to the Seefurth Science School for this opportunity!

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