Devils River Minnow, Dionda diaboli
Note: This Species is currently considered to be ENDANGERED and if encountered should be handled accordingly.
Devils River Minnow, Dionda diaboli. Fish caught from Río Nazas, Durango, August 2014. Length: 6.0 cm (2.4 inches). An accidental catch and an immediate “catch and release.”
Devils River Minnow, Dionda diaboli. Fish caught from the Devils River, Lake View, Texas. June 2021. Length: 6.8 cm (2.7 inches). An accidental catch and an immediate “catch and release.”
The Devils River Minnow, Dionda diaboli, is a member of the Carp and Minnow or Cyprinidae Family, and is known in Mexico as carpa diabla. Globally, there are six species in the genus Dionda, of which five are widespread throughout Mexico’s freshwater systems.
The Devils River Minnow has a slender compressed terete body that are deepest anterior of the dorsal fin origin. They are an overall brownish-silvery color transitioning to silvery-white ventrally. Some fish have dark green bellies. They have a distinct dark horizontal line composed of double dashes that runs from the head to the caudal base. They have a dark spot on the gill cover behind the eye and a wedge-shaped spot and the base of the caudal peduncle and all fins are pale in color and short and rounded. They are sexually dimorphic with breeding males having tubercles evenly distributed over the top of their heads and onto the pectoral fins and yellow fins and a blue-green sheen on the body and anterior portions of the head. Their head is elongated with a pointed snout with large-sized eyes and a slightly sub-terminal mouth. Their anal fin has 8 rays; their caudal peduncle is wide; their caudal fin is concave with wide lobes; their dorsal fin has 8 or 9 rays; and, their pectoral fins have 13 to 16 rays; and, their pelvic fins have 6 to 8 rays. They are covered with large scales. Their lateral line is straight.
The Devils River Minnow is a freshwater benthopelagic that is found in slow-moving, clear, spring-fed waters with gravel substrate and fast-flowing vegetated runs and backwaters with temperatures between 15.7oC (60.3oF) and 30.6oC (87.1oF). They reach a maximum of 6.4 cm (2.5 inches) in length. They are herbivores that consume algae and other plant materials. Reproduction occurs in small groups with external fertilization with early maturation, long spawning seasons and multiple batches. They have life spans of less than three years. The Devils River Minnow 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 Devils River Minnow is native to the freshwater systems of northern mainland Mexico being limited to the Atlantic slope of the Bravo, Conchos, Nazas, Salado, and San Carlos Ríos, of the Río Grande drainage in the States of Chihuahua, Coahuila and Durango.
The Devils River Minnow is a straight forward identification that might be confused with the Manantial Roundnose Minnow, Dionda argentosa (longer and stouter bodies; lack cross-hatch scales and double dashes along the lateral line); and the Roundnose Minnow, Dionda episcopa (deeper body, lacks double dashes along the sides; smaller eyes; round spot on the caudal peduncle).
From a conservation perspective the Devils River Minnow is currently considered to be ENDANGERED which is attributed to its limited range distribution. Their long-term survival is threatened by changes in water quantity and quality with pollution caused by human development including dam construction and the introduction of foreign taxa including the non-native Armored Catfish and Smallmouth Bass. They are small in stature, rare, and of limited interest to most.