The term "catfish slender mouse fish" can refer to a few different species, but it most commonly refers to the slender madtom (Noturus exilis) or similar "mouse catfish" from South America. The slender madtom is a small, slender catfish that is typically three to five inches long, with a yellowish-brown back, a pale underside, and dark-edged fins. Other fish that might be called a "mouse catfish" have a slender body and can have a dolphin-like head profile, such as the dolphin mouse catfish (Tenellus trimaculatus), which has three distinct dark spots along its flanks and can grow to about 4–6 inches.
Slender Madtom (Noturus exilis)
Size: 3–5 inches long, with a maximum of about 6 inches.
Color: Yellowish-brown back and sides, white or pale yellow belly.
Fins: Dark-edged or darker along their outer margins.
Pectoral fin: The spine has saw-like teeth along the rear margin.
Jaw: Upper and lower jaws are nearly equal in length.
Habitat: Rocky riffles, runs, and pools of clear creeks and small rivers.
Dolphin Mouse Catfish (Tenellus trimaculatus)
Size: 4–6 inches (10–15 cm) in captivity.
Color: Slender body with three distinct dark spots along the flanks.
Profile: Subtly dolphin-like profile, especially in the head shape.
Behavior: Peaceful but shy and nocturnal.
Origin: Amazon and Orinoco River basins in South America.
The term "catfish slender mouse fish" can refer to a few different species, but it most commonly refers to the slender madtom (Noturus exilis) or similar "mouse catfish" from South America. The slender madtom is a small, slender catfish that is typically three to five inches long, with a yellowish-brown back, a pale underside, and dark-edged fins. Other fish that might be called a "mouse catfish" have a slender body and can have a dolphin-like head profile, such as the dolphin mouse catfish (Tenellus trimaculatus), which has three distinct dark spots along its flanks and can grow to about 4–6 inches.
Slender Madtom (Noturus exilis)
Size: 3–5 inches long, with a maximum of about 6 inches.
Color: Yellowish-brown back and sides, white or pale yellow belly.
Fins: Dark-edged or darker along their outer margins.
Pectoral fin: The spine has saw-like teeth along the rear margin.
Jaw: Upper and lower jaws are nearly equal in length.
Habitat: Rocky riffles, runs, and pools of clear creeks and small rivers.
Dolphin Mouse Catfish (Tenellus trimaculatus)
Size: 4–6 inches (10–15 cm) in captivity.
Color: Slender body with three distinct dark spots along the flanks.
Profile: Subtly dolphin-like profile, especially in the head shape.
Behavior: Peaceful but shy and nocturnal.
Origin: Amazon and Orinoco River basins in South America.
