Pale Catfish, Rhamdia guatemalensis

Pale Catfish, Rhamdia guatemalensis. Fish caught from Barton Creek, Belize, October 2012. Length: 12.0 cm (4.7 inches). Catch, photograph, and identification courtesy of Josh Leisen (joshadventures.com), Gaylord, Michigan.

Pale Catfish, Rhamdia guatemalensis. Fish caught from coastal waters off Puerto Chomes, Costa Rica, March 2021. Length: 20 cm (7.9 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

Pale Catfish, Rhamdia guatemalensis. Underwater photographs taken in Cenote Azul, Quintana Roo, December 2020. Photographs courtesy of Bob Hillis, Ivins, Utah.

The Pale Catfish, Rhamdia guatemalensis, is a member of the Seven-finned Catfish or Heptapteridae Family, and is known in Mexico as juil descolorido. Globally, there are eight species in the genus Rhamdia, all of which are found in the freshwater systems of mainland Mexico.

The Pale Catfish has an elongated and easily recognizable “catfish-like” body with 3 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 and some populations have a dark stripe on their sides. They have exceedingly long barbels that extend from their head to beyond the pelvic fin origin. Their adipose fin is long and originates before the anus; it is closer to the dorsal fin than to the caudal fin; their caudal fin is deeply forked with wide lobes; and, their pectoral fins are serrated on both the anterior and posterior margins.

The Pale Catfish is a demersal species found in a wide variety of freshwater habitats and is found from sea level to at elevations up to 826 m (2,700 feet) in tranquil waters 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 23.0 cm (9.1 inches) in length. They have an acute sense of smell. They are opportunistic feeders and active carnivorous scavengers that consume aquatic insects, crustaceans, terrestrial invertebrates, and small fish. The Pale Catfish is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.

The Pale Catfish are found in all freshwater systems in southern mainland Mexico in both the Atlantic and Pacific Ocean drainages.

The Pale Catfish is fairly similar to the seven other Rhamdia catfish found in Mexican freshwater systems but has the longest barbels and its pectoral fins are serrated on both margins.

From a conservation perspective the Pale Catfish has not been formally evaluated but should be considered to be of Least Concern with stable widely distributed populations. They are small in stature and of limited interest to most.