South American Catfish, Rhamdia quelen
South American Catfish, Rhamdia quelen. Fish caught from an irrigation canal in Homestead, Florida, July 2021. Length: 16 cm (6.3 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.
South American Catfish, Rhamdia quelen. Fish caught from the Amazon River, Oran, Peru, August 2016. Length: 18 cm (7.1 inches). Catch, photograph, and identification courtesy of Kenneth Tse, Toronto, Ontario, Canada.
The South American Catfish, Rhamdia quelen, is a member of the Seven-finned Catfish or Heptapteridae Family, that is also known as the Silver Catfish and in Mexico as juil de Sudamerica or simply bagre. Globally, there are eight species in the genus Rhamdia, all of which are found in the freshwater systems of mainland Mexico.
The South American Catfish has an elongated and easily recognizable “catfish-like” body with three pairs of barbels. They are dark gray dorsally, dusky on their sides, and white ventrally with golden tinges throughout. Their caudal and dorsal fins are dusky and their other fins are white with yellowish tinges. They vary in color based on location.
The South American Catfish is a demersal species found in a wide variety of freshwater habitats and at depths up to 3 m (10 feet) in tranquil waters, with temperatures between 18oC (64oF) and 28oC (82oF) without high water flows and with an abundance of plant material and heavy substrate such as rocks and stones which they use as shelter during the day. They reach a maximum of 47 cm (19 inches) in length and 4.0 kg (8 lbs 13 oz) in weight. They have an acute sense of smell. They are active nocturnally, being opportunistic feeders and active carnivorous scavengers, consuming aquatic insects, crustaceans, terrestrial invertebrates, and small fish. Their caudal fin has equal sized lobes and their pectoral fins are serrated on both sides. They have 5 to 16 gill rakers. They possess poisonous spiny rays which they rely on for defense against predation. They are aggressive towards conspecifics. Females normally outnumber males by 2:1. Reproduction involves the forming of aggregates for external fertilization, with each female depositing demersal eggs that hatch within forty-eight hours and the larvae develop quickly.
South American Catfish are found in all freshwater systems in southern mainland Mexico in both the Atlantic and Pacific Ocean drainages of the States of Campeche, Chiapas, Oaxaca, Tabasco and Yucatán.
The South American Catfish is fairly similar to the seven other Rhamdia Catfish found in Mexican freshwater systems, but have medium-sized eyes, pectoral fin spines that are serrated on both sides, equally shaped caudal fin lobes, and 5 to 16 gill rakers.
From a conservation perspective the South American Catfish is currently considered to be of Least Concern with stable widely distributed populations. Their long-term survival is threatened by competition from other Seven-finned Catfishes of the Heptapteridae Family, large amounts of fungicides, herbicides and pesticides from agricultural run-off and via trematodes. They are raised throughout South American via aquaculture as a food fish for humans in small ponds and lakes and are easy to maintain, fast-growing, hardy and resistant to temperature changes. They are also pursued by recreational anglers in some regions.