The pejelagarto, known in English as Tropical Gar (Atractosteus tropicus), is a freshwater fish found in the rivers and bodies of water in Central and North America, particularly in the Gulf of Mexico region. This ancient fish, dating back to the time of dinosaurs, has captured the attention of both scientists and anglers due to its impressive appearance, behavior, and unique adaptations.
In recent years, the Tropical Gar has attracted the interest of aquaculturists because its meat is highly consumed in Mexico, primarily in Tabasco.
In this article, we will explore everything you need to know about the Tropical Gar, from its ecology to its cultural and gastronomic significance, and experiences in rearing this fish.
What is a pejelagarto?
The Tropical Gar is one of the few survivors of an ancient group of fish that has changed little over millions of years. Its prehistoric appearance, with an elongated body and hard scales, makes it easily recognizable. This fish has developed several adaptations that allow it to survive in the turbid and low-oxygen waters of its habitat.
The pejelagarto gets its peculiar name from its appearance, with a head resembling that of a lizard and a body like that of a fish. Beyond its appearance, consuming dishes prepared with this fish is a must-do activity if you visit Tabasco.
Due to its characteristics and appeal as a predator, several species of Tropical Gar are sold as ornamental fish for aquariums; however, due to recent demand, interest in the aquaculture of this species has increased.
Distribution and Habitat of the Tropical Gar
The Tropical Gar is primarily a freshwater fish, though it is occasionally found in estuaries. It is distributed across North and Central America, from southern Quebec to Costa Rica. According to researchers, there are seven described species, with distribution limited to the Atlantic Ocean coasts, Gulf of Mexico, and Caribbean Sea.
The pejelagarto inhabits wetlands with rivers and shallow lagoons with abundant aquatic vegetation. It thrives in tropical climates with average water temperatures ranging from 28 to 32°C in summer and down to 18°C in the colder months of the year.
General Information on the Tropical Gar
- Kingdom: Animalia
- Phylum: Chordata
- Class: Actinopterygii
- Order: Lepisosteiformes
- Family: Lepisosteidae
- Genus: Atractosteus
- Species: Atractosteus tropicus
- Common Names in Spanish: Pejelagarto, peje lagarto, catan, manjuarí, pez armado, machorra, or pez Gaspar.
- Common Names in English: Tropical Gar, Gaspar, pejelagarto.
Tropical Gars belong to the family Lepisosteidae, which includes two genera and seven living species. According to Arias-Rodríguez et al. (2009), five species are distributed in eastern North America from southern Canada to northern Mexico (A. spatula, L. oculatus, L. platostomus, L. osseus, L. platyrhincus), A. tristoechus on the island of Cuba, and only the Tropical Gar (Atractosteus tropicus) is found from southeastern Mexico to southern Costa Rica.
Characteristics of the pejelagarto
The Tropical Gar can grow up to over one meter in length and weigh around 15 kilograms on average; however, males have been reported to reach up to 125 cm in length and weigh 28.9 kg. The fish’s body is covered with ganoid scales, which are extremely hard and provide formidable protection against predators. One of the most striking features of this fish is its ability to breathe air. The pejelagarto is a facultative air-breather, meaning that while it primarily breathes through its gills, it can surface and breathe air when the oxygen in the water is low.
Reproduction of the Tropical Gar
Tropical Gars reproduce exclusively in freshwater. Most pejelagartos breed in their natural environment between April and early June. However, there are now methods for artificially reproducing them.
Sexual Maturation
Males mature in their first year (36-42.5 cm), while females mature and spawn in their second year (36-48.5 cm). However, female Tropical Gars only reach their full reproductive potential in their third year.
Sexual Dimorphism
The difference between males and females during the breeding season is evident by the notable bulging and plasticity of the abdomen in females.
A single large female can spawn with several smaller males. A female can lay an average of 8,000 to 12,000 eggs per kilogram of body weight. Mature eggs measure about 3 mm in diameter, are green, toxic, and very sticky, adhering to the surface of aquatic plants, submerged logs, or stones.
It is important to note that Tropical Gar eggs are toxic to humans and should not be consumed.
Induction of Spawning
Some researchers have achieved artificial reproduction of the Tropical Gar using commercial hormones like OVAPRIM-C, with a dose of 0.2 mg/kg of female, observing a response time of 10 to 12 hours. They achieved total spawns with a fertilization rate of 92% and a hatching rate of 98%.
From the experiments conducted by scientists, it was determined that a temperature of 35°C accelerates embryo development, and hatching begins at 35 hours, with a survival rate of 75% until the first feeding.
What Does the Tropical Gar Eat?
The Tropical Gar is a voracious predator. Its diet mainly consists of smaller fish but can also include crustaceans and other aquatic invertebrates. It uses its long snout filled with sharp teeth to capture prey. Although it is a solitary hunter, its behavior changes during the breeding season.
Feeding of Tropical Gar Larvae
In the wild, pejelagarto larvae consume zooplankton (cladocerans, copepods, insect larvae, and fish larvae). Juveniles include aquatic insects and fish in their diet, while adults consume other fish (ichthyophagous), occasionally eat zooplankton, and are often opportunistic scavengers.
According to research reports, once the larvae hatch, exogenous feeding begins 72 hours after hatching, capturing live food (cladocerans, mosquito larvae, small insects). Research results indicate that the endogenous feeding phase (yolk or vitellus) ends when 50% of the larvae show stomach content, starting the mixed feeding phase (yolk and live food).
The mixed feeding phase of pejelagarto larvae begins between 120 and 128 hours post-hatching. Maytorena et al. (2022) recommend including mannan-oligosaccharides as prebiotics in the diet of A. tropicus larvae at a concentration of 6 g/kg of food; Pérez et al. (2022) recommend supplementing the diet with fructooligosaccharides (FOS) at a rate of 7.5 g/kg.
Larvae fed exclusively with Artemia grow faster; however, due to cost issues, combinations of water fleas (80%) and Artemia (20%) are recommended to achieve significant growth and survival rates.
Recent research by Escalera et al. (2018) demonstrated that Tropical Gar larvae prefer combinations of Artemia and the cladoceran Moina macrocopa. They recommend a mix of A. franciscana and M. macrocopa to feed the larvae in culture systems at concentrations of 2 ind/mL during the first three weeks of age and then switching to M. macrocopa from the fourth week onward.
Meanwhile, De La Cruz-Marín et al. (2023) recommend including 2.0% and 2.5% inulin in the diet of A. tropicus larvae to improve survival and digestive enzyme activity.
Feeding Frequency
Regarding feeding frequency, research results recommend feeding 5 to 6 times per day. Here are some recommendations for feeding the Tropical Gar at different stages of its growth phase:
- Days 1-10: Provide live food (Artemia and water fleas) until the larvae reach a size of 28 to 45 mm.
- Days 11-16: Provide a mix of live food and powdered artificial feed (32 to 45% protein and 17% lipids).
- From Day 17: Feed exclusively with balanced food (32 to 45% protein and 9% lipids) in powder form.
- Pre-fattening Phase: Feed fingerlings with balanced food (32 to 45% protein) in sizes of 1.5 and 2.5 mm.
- Fattening Phase: Feed Tropical Gar with artificial food (32 to 45% protein) in sizes of 2.5, 3.5, and 5.5 mm in diameter.
Feeding of Juvenile Tropical Gars
Guerrero-Zárate et al. (2024) studied the in vitro digestibility of various ingredients commonly used in Tropical Gar feed. They used digestive enzymes extracted from the stomach and intestines of juvenile pejelagarto to simulate how the fish break down different foods. The main conclusions of the study were:
- The Tropical Gar can efficiently digest a wide variety of protein sources, including fish meal, crustacean meal, beef, poultry meat and offal, and even beef blood meal.
- In terms of fats and oils, the pejelagarto showed a preference for soybean lecithin, cod liver oil, and common vegetable oils such as soybean, olive, corn, and canola oil.
Raising Tropical Gars
Large pejelagarto species are preferred by certain groups of fishermen, and their meat is valued in the southern United States, Mexico, Cuba, and Costa Rica.
In Mexico (A. tropicus) and Cuba (A. tristoechus), there are larval rearing laboratories for growing fish in ponds or for commercialization to aquarium fish distributors.
Physical-Chemical Parameters
The main water quality parameters for raising Tropical Gars are:
- Water Temperature: 18 to 37°C, with an average of 28 to 32°C
- Dissolved Oxygen (for incubation and larval rearing): 3 to 6 mg/L
- Water pH: 7 to 8, with an average of 7.5
- Water Hardness: 6-16 °dH
- Minimum Aquarium Size: 1325 liters
- Breeding Density in an Aquarium: 2:3 Males
Martínez et al. (2021) used A. tropicus embryos as a model to study survival, growth, and development of the fish under different conditions of temperature (control 28°C, 33°C, and 36°C), salinity (control 0.0 ppt, 4.0 ppt, and 6.0 ppt), and air saturation (control ~95% air saturation, hypoxia ~30% air saturation, and hyperoxia ~117% air saturation) during three developmental periods: (1) fertilization to hatching, (2) day 1 to day 6 post-hatching (dph), and (3) day 7 to 12 post-hatching (dph).
They found that:
- Elevated temperature, hypoxia, and hyperoxia decreased survival during incubation and salinity at 2 and 3 dph.
- Growth increased in embryos incubated at elevated temperatures, higher salinities, and hyperoxia, but decreased under hypoxia.
- Developmental changes occurred as alterations in hatching timing, yolk depletion, acceptance of exogenous feeding, free swimming, and snout shape changes, especially at high temperatures and hypoxia.
On the other hand, Cordova et al. (2022) determined that the larval development of pejelagarto (Atractosteus tropicus) is dependent on thermal regime during embryonic development. In summary, incubation temperature directly affects the growth of A. tropicus larvae.
Larval and Juvenile Stocking Density
Researchers have evaluated stocking densities of up to 40 larvae per liter, achieving an average survival rate of 95.6%. The larval phase lasts approximately one month. However, Sepúlveda et al., (2024) found that the best growth of A. tropicus larvae occurred at a density of 1.4 larvae per liter with feeding.
Sepúlveda et al., (2023) studied the number of cannibalism attacks during the larval phase and reported that the highest number of group attacks was observed with pink, blue, yellow, and purple background colors, with purple being less effective. The presence of shelters (artificial vegetation) reduced attacks in pairs and groups compared to using rocks as shelters. Sepúlveda et al., (2024b) did not record aggressive behaviors in larvae fed with a 10 g/kg tryptophan (Trp) treatment.
Martínez et al. (2020) recommend a stocking density of 200 fish per cubic meter for juveniles averaging 9 cm in length and 3.80 g in weight.
Fattening Phase
The pre-fattening phase begins after one month of larviculture when the fry are transferred to pre-fattening cages. This phase lasts 2 months and ends when the fry reach 10 cm.
The fattening phase lasts between 6 and 8 months, concluding when the fish reach 500 grams.
If you are interested in Tropical Gar aquaculture, you can visit the INAPESCA website for more information.
Consumption of Tropical Gar
The Tropical Gar is of significant gastronomic and cultural importance in southeastern Mexico (Ortiz et al., 2015). This fish is marketed fresh whole and frozen, primarily.
The spiny meat of the pejelagarto is consumed grilled, accompanied by tortillas and salsas. Márquez and Vázquez (2018) highlight that in Tabasco, the local society has developed a particular taste for Tropical Gar, and its consumption includes a wide variety of dishes such as grilled Tropical Gar, tamalito, empanadas, salad, and chirmol, among others.
Ortiz et al. (2015) evaluated the acceptability of meat from farmed and wild fish. They reported significant differences in flavor and overall acceptability, noting that farmed Tropical Gar was most acceptable.
Conservation and Threats
Despite its adaptability, the pejelagarto faces several threats, primarily due to habitat degradation and overfishing. Pollution of rivers and the destruction of wetlands for agriculture and urban development have significantly reduced the areas where these fish can live. However, due to its cultural and gastronomic importance, there is growing interest in conserving this species, both in Mexico and in other countries within its distribution range.
Conclusion
The Tropical Gar is much more than a prehistoric fish; it is a living treasure that has withstood the test of time, adapting and surviving in challenging environments. Its history, cultural significance, and unique behavior make it a fascinating species for both scientists and the general public. As we face a future with increasing environmental challenges, the conservation of species like the pejelagarto becomes more crucial than ever. Preserving its habitat and ensuring its survival not only maintains a part of the past but also allows us to continue enjoying one of the most iconic fish of Central America.
In summary, the pejelagarto is an impressive example of how life can adapt and thrive over millennia, and its preservation is vital for both biodiversity and the human cultures that depend on it. Conserving this species and its habitat ensures that future generations can appreciate and learn from this remarkable inhabitant of tropical rivers.
References
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