- More than 200 oil leak or spill events have been reported by Pemex in the last five years in Tabasco.
- To compensate Gulf of Mexico fishermen affected by sea pollution, the state of Tabasco is implementing a plan to repopulate lagoons with tilapia fish.
- More than 27,000,000 baby tilapia have been released in Tabasco's lagoons in the past five years.
- This fish, native to East Africa, is considered an invasive species and causes concern among scientists due to its potential impacts on biodiversity that have not yet been measured.
The fishermen of the El Arrastradero lagoon, facing the Gulf of Mexico, are waiting for the medium-term benefits of tilapia sown on December 12, when Mayor Alfonso Baca Sevilla posed in front of the cameras to inaugurate the lagoon repopulation program in the municipality of Paraíso. On a boat in the middle of the lagoon, several leading fishermen accompanied the mayor, grabbed a bunch of bags and released 52,000 nilotic tilapia, a fish that science calls oreochromis niloticus.
In an interview, the Director of Development of the City of Paraíso, Santiago Magaña Burelo, said that oil spills in the sea are part of the reasons why this program is being promoted. The last incident gained national notoriety when a spill of 300 barrels of crude oil from the Akal-C pipeline of the Campeche Sonda became visible in May, which was carried by currents to the beaches of Paraíso.
In the last five years, Pemex alone has experienced 201 oil leaks or spills. These are at least 1,650,000 liters discharged “into the environment”, both in marine and terrestrial extraction fields, although most of these data provided by the oil company (60%) do not record the amount spilled.
“The idea comes about because in reality there has been a lot of pollution in fresh and salty waters, and obviously the fishermen have suffered a lot because they go fishing and they can't find anything. We are providing them with support, because Paraíso has a lot of waters and those waters are not used,” Magaña explained about this program carried out in freshwater bodies close to the sea.
The spills have scared away fish stocks offshore, forcing fishermen to spend more gasoline to reach fishing areas, according to the local federation of fishing cooperatives, which maintains a claim to Petrleos Mexicanos (Pemex) to be compensated for these damages. So far they have managed to buy them new fishing gear and increases in gasoline supplies.
This is not the first time that oil production accidents have impacted Paraíso and cooperatives not aligned with the leaders of the local federation are taking advantage of the change in the municipality's fisheries policy, now focused on lagoons. José del Carmen Díaz abandoned marine fishing decades ago due to oil leaks and is currently secretary of the cooperative Union of Jerusalem, one of the petitioners of the repopulation. Local fishermen, he says, are expecting the reproduction of the released tilapia fry.
In December 2024 and the first half of 2025, the City Council of Paraíso planted 177,000 Nilotic tilapia fry in four lagoons: El Arrastradero, Tres Palmas, Puente de Ostión and Tupilco. The problem is that Nilotic tilapia, native to the Nile River basin in East Africa and the Middle East, is an invasive species that, according to scientists and experts, can have serious repercussions on biodiversity and ecological balance.
Between pollution and pups
Local fishermen from the El Arrastradero lagoon said they had asked the municipal government to repopulate with tilapia. Photo: Michel Entrada.
“There were some comments that tilapia was predatory, that I don't know what, that's a lie. The mojarra [as fishermen also call tilapia] has adapted so much that it coexists [with native species] here in these waters. You go and fish, you throw a clown [lure] and you're going to grab castarrica, paddles and tilapia,” said del Carmen Díaz.
The empirical experience of fishermen is not contrary to the scientific one in fact, but the interpretation differs.
Dr. Manuel Mendoza Carranza, a researcher specializing in Biological Oceanography at the Colegio de la Frontera Sur in Tabasco, argues that tilapia is known to compete with native species, which tends to cause native populations to diminish without necessarily disappearing.
“In Tabasco or in southern Mexico, there are several native species, but their fisheries have declined or have been overshadowed by the high abundance of tilapia,” says Mendoza Carranza. The reason, explains the expert, is that tilapia competes for food and space with native fish. “This obviously has an effect on other species that see their populations diminished, but not disappeared,” he says.
The latest version of the National Aquaculture Charter dates from 2022 and states that nilotic tilapia is an “exotic” species and that “the ecological and health repercussions that its presence may have on the lagoon system is unknown”.
An analysis published by the National Commission for the Knowledge and Use of Biodiversity (Conabio), prepared by Dr. Roberto Mendoza Alfaro in 2014, together with Sergio Luna, Yésica Gómez and Porfirio Álvarez, gives nilotic tilapia a degree of invasiveness of 40 points, which classifies it, within the methodology of the study, as a highly invasive species. This work is taken up by the Conabio technical data sheet on the species and which confirms this condition.
Dr. Guillermo Giannico, professor in the Department of Fisheries, Wildlife and Conservation Sciences at the University of Oregon, explained that man has been a factor in the artificial introduction of species into natural environments that were not his own.
“There is no shortage of freshwater fish in Mexico. It has an impressive biodiversity, perhaps one of the highest in the world along with the rest of Central America, Colombia, Venezuela and part of Brazil. But somehow those who have been interested in producing fish meat, let's say, 'without going to fish in the sea', found out that there were opportunities with certain freshwater fish. Thus, tilapia, which is native to Egypt, began to be raised in different types of artificially dug wells,” he says.
Laboratory fishes
Tilapia fry in a tub in the Cittat. In addition to those intended for repopulation, the center delivers fry to local producers. Photos: Michel Estrada.
Before being released into the lagoons, tilapia are raised at the Tabasco Aquaculture Innovation and Technology Transfer Center (Cittat), which is part of the Mexican Institute for Research in Sustainable Fisheries and Aquaculture (IMIPAS), corresponding to the federal government.
This is a rustic building in front of the Mecoacán lagoon, recently impacted by the Pemex crude oil leak. There, on average, between 400,000 and 500,000 fry are produced every year and are distributed in the region, says the biologist in charge of the City, Alejandro Pérez.
On a tour of the center, technician Pedro de la Cruz explains that tilapia eggs, once collected, are placed in an incubator where they hatch. There they feed on their own yolk sac.
Some of the fry grow to two to three centimeters and are delivered in bags to the municipality for release in the lagoons of Paraíso.
Another part of the fry undergo a hormonal process to seal their masculinity a few days after hatching. This is because males of this species are more valued for their size and the amount of meat they can provide as they fatten, says de la Cruz. When they reach two or three centimeters, the Cittat delivers them to individual producers through the Paraíso City Council.
This center has been producing offspring for fattening in different systems for more than 30 years. From his laboratory, senior technician Lorenzo Pérez Sánchez, who has worked with the genetic manipulation of tilapia, explains that the commitment to this species began in the 70s.
Prior to the hormonization in this center, natural selection processes were experimented with in order to achieve genetic improvement that would help them to obtain as many males as possible and to make them resistant to brackish water in the coastal lagoons of the Gulf of Mexico.
These were species native to Mozambique and Tanzania, with which hybrids were obtained. Lorenzo Pérez explained that red Oreochromis mossambicus was crossed with Oreochromis hornorum, a species that appeared to be aggressive because of the bites that the male gave to the females, whose teeth had to be cut by researchers with razors.
“We put one male for every three females and 75% of the males came out. The problem here is that the lagoons are saltwater, so we started to condition little by little until we managed to have specimens that had resistance,” says Lorenzo Pérez.
Lorenzo Pérez, technician at the Cittat laboratory, in Paraíso Tabasco. Photo: Michel Estrada.
Challenges of repopulation
Alejandro Pérez defines Nilotic tilapia as follows: “It's a very friendly species. Why? Because it's very easy to produce and to fatten.” However, he stresses that once the fish are released in the lagoons, their livelihood is not guaranteed. “Populations within natural bodies of water have not flourished as expected because they are fully adapted to the environmental conditions of our site and because they are preyed upon in juvenile stages by natural species,” he points out.
This situation is supported by local fishermen who perceive that, at the time of liberation, the fry are too small to survive.
“For us, who know, it's a tremendous mistake. For example, tilapia in a lagoon as huge as Acayucan (Veracruz), such as La Flores lagoon (Paraíso), went to feed on other species. They are throwing them away in a size that even castarrica eats it, which is the native species,” explains Santiago García, secretary of the Federation of Fishing Cooperatives of Paraíso.
However, repopulation is effective. This has been verified by Dr. María de Jesús Contreras-García, in charge of the Tropical Aquaculture Laboratory of the Autonomous University of Tabasco (UJAT), which carries out repopulation of tilapia and native species in lagoons in the center of Tabasco. “Tilapia is here to stay because it has certain characteristics that give it certain advantages over native tilapia that take longer to grow. It doesn't mean that we're going to displace or put it above our native species,” he says of the laboratory's effort to also plant native species.
This UJAT laboratory supplies local and exotic species to lagoons in downtown Tabasco and a sister laboratory in Frontera cultivates marine species. Photos: Michel Estrada.
Repopulation evaluations demand scarce resources in the Tabasco academy, however, in 2014 researchers confirmed, through a one-year follow-up carried out with an electric boat, the presence of the specimens in the lagoons after the planting of young. “The samples included zero time before repopulation, after six months and a year, and there was abundance in that period of time in terms of the number of organisms,” says Contreras-García.
In an analysis from the last five years, the number of tilapia babies planted in Tabasco by the 17 municipalities of the entity, the government of that state and the IMIPAS (of federal order) was requested through transparency: the sum is 27,329,000 fry.
Tilapia repopulation map of the three levels of government. Elaboration: Juan Luis García.
The fact that tilapia is already in the water does not justify its continued introduction, points out ecologist Manuel Mendoza Carranza in front of numerous actors who excuse the possible impacts of repopulation on the grounds that tilapia has been in the waters of Tabasco for decades.
“It's a palliative, a justification from my point of view that's not so valid. In fact, there are also species of mojarras here in Tabasco that are not commercial and that have most likely been ecologically affected by tilapia,” says Mendoza Carranza. “There are some small species that do not exceed 15 centimeters, that are part of the ecosystem and that play a role, and that will probably have an effect on them when it comes to introducing all that quantity of tilapia. That's one of the main concerns,” he points out.
Lorenzo Pérez recognizes that tilapia is invasive: “Yes, it's true, because it proliferates too much. At 5 centimeters, at 10 grams, it is already proliferating compared to native species,” he says. However, he argues that in saltwater it reproduces in smaller quantities.
For Mendoza Carranza, however, it is worth asking what is the capacity of the ecosystem to receive introduced species. Saturating a lagoon body with species increases competition, he says.
“There's going to be a lot of competition for space and that's obviously going to cause some species to decline and others that can be more ecologically efficient, such as tilapia, to occupy those empty spaces and that diminishes the biodiversity of the board, so to speak,” he accuses of a kind of ecological chess where the introduced species are the pieces.
It is true that Tabasco's commitment to tilapia will not cease in the short term, since it corresponds to policies supported by the federal government. Tilapia arrived in the country in 1964 at the Temazcal aquaculture center in Oaxaca and later proliferated throughout the country.
In this regard, the study Invasive Aquatic Species in Mexico, led by Dr. Roberto Mendoza Alfaro, highlights the importance of institutions themselves changing their approach and protecting native species.
“Conapesca boasts of having planted several tens of millions of young in the natural environment, mainly tilapia and carp, despite the fact that the commission's powers include coordinating national policy on the rational and sustainable use of fishing and aquaculture resources. As long as there is not enough environmental sensitivity in this commission, our native resources will continue to be at risk,” says the work published by Conabio.
The document highlights that there are ways to replace exotic species, such as implementing repopulation programs with native species; including guidelines for species substitution in the National Aquaculture Charter; encouraging research on native species for commercial purposes; and using risk analysis when introducing exotic species.
Although IMIPAS is responsible for authorizing fish restocking, the Secretariat of Environment and Natural Resources (Semarnat) endorses resolutions on environmental impacts. This body, however, assured Mongabay Latam that it lacks environmental impact studies regarding the repopulation of tilapia in Tabasco in the last five years.
The El Arrastradero lagoon is one of the four chosen by the Paraíso City Council for the planting of Nilotic tilapia. Photos: Michel Estrada.
Asked how it is possible to reverse the presence of exotic species in ecosystems, Dr. Giannico explained: “It's very difficult to reverse the process. The only way it reverses is if the species doesn't adapt.” The latter is no longer an option in the case of tilapia, which has already taken root in the Tabasco tropics.
“In the case of tilapia and other species that are also successful, the question would be why some species are successful in establishing self-sufficient populations and others are not. It has to do with the reproductive rate. There are certain biological characteristics that make certain species better invaders than others,” explains Dr. Giannico.
For example, an omnivorous animal is more likely to adapt than some that eat only certain diets that they rely on for their livelihood. Tilapia feed on small invertebrates, phytoplankton, algae, insects, crustaceans, and plant matter.
On a social level, what has happened with invasive fish stocks is that people have become used to counting on them. One case of entrenchment occurred with rainbow trout and salmon species in Chile, Giannico details.
“People adopt species in many cases as if they were their own, the case of New Zealand, Argentina and Chile is clear, where the population of those countries believes that many of these salmonids, both salmon and trout of various species, are native. If you do an interview on the street, people don't believe or don't know that they were introduced 100 years ago and of course if someone thought of trying to eliminate them, people would rise up against that legislator,” says the expert.
For the city's senior technician Lorenzo Pérez, tilapia, although invasive, has been used as an excuse to divert people's responsibility for the decline of native species due to the destruction of habitats. A man-made affectation that in Paraíso is constantly manifested in hydrocarbon spills.
Santiago Magaña, Development Director of the City of Paraíso, has been in charge of the area of repopulation with tilapia in the town's lagoons. Photo: Michel Estrada.
“Fishing has become complicated because in reality pollution is the one that harms the most. A few days ago [it says June 11] there was very severe pollution, many free fishermen, cooperatives suffered,” says the director of Development of the City Council, Santiago Magaña.
Unable to prevent oil spills, the municipal authorities concentrate their efforts on supporting fishermen with tilapia, something that does not contravene other government orders and seeks to get fishermen to return from the sea to inland waters.
“We are doing the support so that they in their own communities have their work and don't have to go to the deep sea,” Magaña says.
*This report was selected by the Mongabay Latam grant to tell stories about oceans.
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