How to Identify Mexican Stoneroller

To identify Mexican Stoneroller (Campostoma ornatum), look at these key features.

Physical Characteristics

Body shape

elongated

Coloration

Overall olive to brownish-gray dorsally, fading to silvery-white ventrally. Sides often have scattered dark spots or blotches. During breeding season, males develop vibrant orange-red fins (especially pectoral, pelvic, and anal fins) and prominent nuptial tubercles on the head and body. Females may show subdued coloration.

Scale type

cycloid

Mouth position

subterminal

Distinctive features

Cartilaginous lower jaw with a sharp, chisel-like edge for scraping algae., Small, subterminal mouth., Dark lateral stripe often present, especially in juveniles., Prominent nuptial tubercles on breeding males.

Dorsal fin

Single dorsal fin with 8 rays, typically located slightly anterior to the pelvic fins.

Tail fin

Moderately forked caudal fin.

Pectoral fin

Pectoral fins are relatively large and positioned low on the body.

Distinctive fins

Pelvic fins are abdominal. All fins are typically clear to dusky, becoming orange-red in breeding males.

Identification Tips

1. 1

   Mouth Structure

   Look for the unique cartilaginous lower jaw with a chisel-like edge, used for scraping. This is a key diagnostic feature for the genus Campostoma.

2. 2

   Coloration (Breeding Males)

   During spring, breeding males develop striking orange-red fins and numerous, sharp nuptial tubercles on the head and body, making them easily identifiable.

3. 3

   Body Shape and Size

   Small, slender body, typically reaching 10-15 cm (4-6 inches) in length. The body is somewhat compressed laterally.

4. 4

   Habitat Preference

   Often found in clear, flowing waters over rocky substrates, which aligns with its feeding strategy.

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