Giants from the Past: Searching for Mexico's Big Fish

Latest update August 2, 2019 Started on August 20, 2018

Mexico's biggest grouper species are at risk. Three grouper species in Mexico's three principal marine ecosystems grow to two metres or more in length, and all three are endangered. We are working with fishing communities throughout Mexico to investigate the populations of 1) the Pacific kelp forest's Giant Sea Bass (Stereolepis gigas) – Critically Endangered, 2) the Gulf of California rock reef´s Gulf Grouper (Mycteroperca jordani) – Endangered, and 3) the Mesoamerican coral reef´s Goliath Grouper (Epinephelus itajara) – Critically Endangered. We are working with small-scale fisheries trained as SCUBA diving citizen scientists, traditional ecological knowledge and new technology such as hydrophones, to search for these once common species and propose conservation measures.

August 20, 2018
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In The Field

Beginning in the first week of July a team of six community divers from Baja California Sur, Mexico are leading an expedition to look for Giant Sea Bass in the Pacific Kelp forests. They have a lot of experience in marine surveys as they have participated in previous expeditions so they started their own with the support of their fishing cooperatives.

In collaboration with members of , COBI, and two cooperatives, they will go diving every weekend in the Kelp forests and make maps of the reefs where Giant Sea Bass have been seen before.

They found the first fishes on the first weekend of the search and every weekend since they have found at least one grouper of about 60-90 cm of length.

We all hope they will find a lot of groupers!


In Punta Allen, Mexican Caribbean, fishermen have seen not only grouper but snapper spawning aggregations too.
Last month we went there to look for these aggregations! In collaboration with the fishing cooperative “Vigía Chico” and their 11 community divers, we dove in the southern part of Punta Allen searching for snappers ready to spawn. We couldn´t find them but we had a beautiful dive with lots of jacks. Snappers are difficult to find when they´re aggregating to spawn because they often swim around a lot and don´t stay in the exact same point like the groupers.

We won’t stop the search here. Next year we will continue our expedition to find them!


How do you remember the ocean?
The ocean is changing, however, as scientist Daniel Pauly shows us , sometimes we forget how it was in the past.

This summer we´ll be launching our project website! Get a sneak peak at (Giants of the Past) where you can learn more about the biggest fish in Mexico.

Want to see how critically endangered groupers spawn?
Lots of footage from the marine reserve that the fishers created in 2016! Quieres ver como desovan los meros? Varias imágenes de las reservas marinas hechos por los pescadores en 2016!

This week we´re providing the Spanish language diffusion to BelugaSmile´s spawning aggregation conservation communication strategy.
Check out all the videos at

We continue studying the Nassau Grouper spawning aggregation at Punta Allen, Mexican Caribbean. In collaboration with the fishing cooperative “Vigía Chico”, we installed an hydrophone on November, last year, at the spawning site to record the sounds that the Groupers make while they’re aggregated.

To date we have recorded 187 hours of sounds from the marine environment there.

What will the sounds reveal? Our next step is to analize them!

A great expedition, well done!

In Guatemala City to plan fish spawning aggregation work for the Mesoamerican Reef. COBI sharing our experiences in Mexico and how we can replicate them in the other MAR countries


Checkout our new publication on Fish Spawning Aggregations in Mexico!
Available in English and Spanish


We got the Trident in the water! Test dive #1 done!
On a quick trip to Punta Allen we tested the Trident out on the sea grass. All went well, easy to pilot and control. Left the plastic cover on the lense by accident so image a little blurry. Can´t wait to get back in the new year to see some groupers!


Off to a good start, now it's exploring time!

It´s arrived!!
Ya llegó!!

Thanks SEE, OpenROV and David Lang!


Excellent! Excited to hear what you think and see the videos to come!

Our participation in the expedition in Baja California was a great success. Many giant sea bass seen by the divers and fishers.

Giant Sea Bass Expedition in Baja, Mexico

We were able to document the presence of giant sea bass in almost every site we visited in this expedition across Baja. We found an aggregation of sexually mature individuals and we recorded their courtship behavior. Although we try, we couldn't document the spawning event,...on this time. We'll look forward to keeping working together with the fishers cooperatives, COBI, others NGO's and the government agencies. Video by Ben Meissner

Posted by Mero gigante project on Wednesday, September 5, 2018

Our team, alongside members of and several fishing cooperatives in Baja California, is searching for Giant Sea Bass in the Pacific Kelp forests. The team (made up of fishers, researchers and NGO staff) is SCUBA diving at key spots along the coast. What will they find?
(photo: Ben Fiscella Meissner)


Check out our new paper published in the journal Citizen Science: Theory and Practice -

Working with the fishers is the best way to find and protect spawning sites. They almost always know exactly where the sites are, but robust scientific methods should be included, as well as effective, adaptive management.


Awesome! This is a great paper.


Have you been SCUBA diving in Mexico? Report sighting of big grouper species using iNaturalist and Naturalista to help us identify hot spots!

¿Has estado buceando en México? ¡Reporte avistamientos de los peces grandes (por ejemplos meros) a través de Naturalista para ayudarnos identificar sitios importantes

Expedition Background

Building on support provided by OpenRov (amongst others) in 2015 to investigate a Nassau Grouper spawning site in the Sian Ka´an Biosphere Reserve, we were able to work with the progressive fishing cooperative “Vigia Chico” to protect what may be the biggest Nassau Grouper spawning site in the Mexican Caribbean. A neighbouring cooperative to the south, “José María Azcorra” has also protected grouper and snapper spawning sites (since 2013) and one no take zone contains resident Goliath Grouper. With additional donor support we have been able to expand our focus to all the areas where our organization ( works to search for the most emblematic large fish species in the 31 marine reserves that our community partners have established in the past decade. We are collaborating with teams of national and international researchers, 16 fishing communities and over 100 trained fishermen and women to reach our goals.


I work with Comunidad y Biodiversidad (COBI, Our marine reserves team who dedicate time to this is made up of nine people - in the Mexican Caribbean (Cancun), Gulf of California (Guaymas) and Baja California (La Paz). We also work very closely with >20 fishing communities, and the fishers provide a lot to the project - they are great allies! Over the years we´ve trained >200 fishers (men and women) to SCUBA dive so we have lots of eyes in the water!

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