From coexisting with dinosaurs and surviving five mass extinctions, the Cuban manjuarí fish (Atractosteus tristoechus, or Cuban gar) today faces two threats that could finally break its historical resilience: the African Walking Catfish (Clarias gariepinus) and humanity.
Scientists have struggled to track its population for decades, nearly losing sight of this remarkable fish despite its notable characteristics: a cylindrical, elongated body up to 60 inches long, covered in stone-like plates.
The manjuarí fish, designated as one of the most emblematic fish on the island, has been labeled as “critically endangered” on the Red List of the International Union for Conservation of Nature (IUCN) since 2020. This classification signifies a population decline of over 80 percent, primarily due to habitat degradation and invasive species.
How the Cuban Gar Has Survived
The fish with "many teeth" was already a staple in the diet of the first inhabitants of the Caribbean island at the time of the Spanish conquest.
However, its lineage goes back much further, some 240 million years, and includes the history of today's seven gars (Lepisosteiformes), the most primitive bony freshwater fish that, according to Timothy J. Lyons, IUCN Aquatic Species Red List officer at the New Mexico BioPark Society, “have remained relatively unchanged over millennia because they are very effective predators.”
Although it is an oxymoron, the manjuarí is considered a “living fossil” due to its enormous similarity to its (very) ancient relatives. It is a term that Erik García-Machado, a researcher at the Marine Research Center of the University of Havana in Cuba and the Institut de Biologie Intégrative et des Systèmes of Université Laval in Québec (Canada) and his colleague Gabriela Ulmo-Díaz deny academically. Still, it is easy to understand if you want to draw urgent attention to its conservation.
“The manjuarí has evolved like any animal; however, it indeed maintains characteristics that one could consider typically primitive,” clarified García-Machado.
For example, their skeletal system contains a large amount of cartilage instead of bone, and their vertebrae are opisthocoelous, meaning the anterior ones are convex and the posterior ones are concave.
For Lyons, gars in today's world are capturing the public's interest. “They remove the veil of time from a world before humans,” he said. And, in this sense, “large and charismatic species like the manjuarí can be a model for freshwater conservation.”
A great task when they have almost everything against them.
Read More: What Animals Are Going Extinct?
A Mysterious Creature
That is why the first word that comes to mind for García-Machado, is “unknown.”
Its current distribution is unknown, as is its population size, because it is difficult to find specimens within the Ciénaga de Zapata National Park (Matanzas province, located 100 kilometers from the tourist city of Varadero), where they have been restricted. Additionally, during the last survey, none were found in the swamps of the Isle of Youth (southwestern part of Cuba).
Before 1999, between 150 and 200 individuals were observed per linear kilometer in the Zapata Swamp. However, various counts in the last 10 years have found between one and five.
The manjuarí is also a mystery because it is not known if the few conservation efforts in the area are working or if the protection measures have been effective. The capture, killing, or unauthorized trade of the manjuarí has been considered illegal since 1996, and its status as a species of special importance was approved in 2011.
“I am not optimistic,” García-Machado confessed.
Neither is Lyons, who put it plainly: the species' problems “have not ceased and may not be easily reversible.”
Is There Hope for the Endangered Manjuarí?
The worst enemy of the Cuban fish is a species introduced for food in 1999 that has since conquered all of mainland Cuba and the Isle of Youth. "It is extraordinarily voracious," García-Machado described.
It consumes juvenile manjuarí and destroys all the endemic freshwater ichthyofauna. In comparison, the behavior of the native fish, although carnivorous, is not aggressive.
The uncontrolled presence of the African Walking Catfish hinders, any attempt to reintroduce the manjuarí. One option for the manjuarí is to be bred in captivity until it exceeds the size it is vulnerable to predation. But, again, it is “unknown” whether it can survive in nature.
Human activity has caused the Zapata Swamp to lose significant areas of marshes, mangroves, and hardwood forests in recent decades. Despite these losses, it remains the best-preserved and largest wetland in the Caribbean, having been designated a Biosphere Reserve and a Ramsar Wetland of National Importance at the beginning of the century.
However, until recently, about 60 manjuarí breeders were being raised at the Center for Indigenous Ichthyofauna Reproduction (CIIR) at Zapata Swamp under the care of Andrés Hurtado. Some young specimens have already been released, but it is unknown whether they have survived.
The life cycle of the manjuarí itself is another element that works against it: males begin to reproduce between 3 and 4 years of age, and females do so later; on average, the species can live up to 25 years. In the center, some specimens have already surpassed a decade of life, which is believed to have already affected their reproductive capacity.
Part of the sad reality is that the manjuarí is alone. The closest species of the other gars, A. spatula (known as Alligator Gar), inhabits eastern North America. Their genetic differences are quite notable, and although they can hybridize, Ulmo-Díaz maintains that it would be an effort as titanic as it is useless.
“The genetic pool of the manjuarí is not large enough for this to be feasible with the conditions that exist right now,” she stated.
And she added: “The main challenge is to achieve survival. We have ideas of things that can be done to help the species, but we cannot say exactly what state it is in, where it is, or in what quantity.”
One possibility is to conduct an environmental DNA study in the Zapata Swamp, which García-Machado and Ulmo-Díaz estimate could be completed within a year. It is a non-invasive technique that allows for obtaining information about the biodiversity of an ecosystem, but although it is low cost, economic resources are still needed, in particular, to access the most remote parts of the site.
However, Ulmo-Díaz is the only one who dares to reveal her optimism.
"The CIIR has a good mix of breeders, and the natural areas could be recovered to be in a position to accept a certain number of individuals." She does not doubt: "I think we can achieve their subsistence." We just have to take the first step.
Read More: Scientists Are Trying to Save These Animals From Extinction
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
International Union for Conservation of Nature Red List. Manjuarí
Researcher at the Marine Research Center of the University of Havana in Cuba. Erik García-Machado
IUCN Aquatic Species Red List Officer at the New Mexico BioPark Society. Timothy J. Lyons
Researcher at Marine Research Center of the University of Havana. Gabriela Ulmo-Díaz
