How to Identify Bullhead

To identify Bullhead (Cottus gobio), look at these key features.

Physical Characteristics

Body shape

elongated

Coloration

Dorsally, they are typically mottled brown, grey, or olive, providing excellent camouflage against the riverbed. The flanks are lighter with darker blotches or bands, and the belly is pale, often whitish. Fins are usually banded or spotted.

Scale type

none

Mouth position

terminal

Distinctive features

Large, broad, flattened head, wider than the body., Large, upward-pointing eyes., Absence of scales on the body, which is instead covered in small prickles (spinules) or is smooth., Two dorsal fins, the first spiny and the second soft-rayed., Broad, fan-like pectoral fins., Pelvic fins are thoracic, located beneath the pectoral fins.

Dorsal fin

Two dorsal fins: D1 (spiny) with 6-9 spines; D2 (soft-rayed) with 15-18 rays. The first dorsal fin is typically shorter than the second.

Tail fin

Caudal fin is rounded or slightly emarginate, with 10-12 rays.

Pectoral fin

Large and fan-shaped, with 13-15 rays, extending well beyond the origin of the anal fin.

Distinctive fins

Pelvic fins are thoracic, with 1 spine and 3-4 soft rays, often appearing as a single, broad fin.

Identification Tips

1. 1

   Head Shape

   Look for the distinctively large, broad, and flattened head, which is wider than the rest of the body.

2. 2

   Body Covering

   Note the absence of true scales; the skin is either smooth or covered in small, prickly spinules, giving it a rough texture.

3. 3

   Fin Placement

   Observe the large, fan-like pectoral fins and the thoracic pelvic fins located directly beneath them.

4. 4

   Coloration and Pattern

   The mottled brown/grey/olive coloration with darker blotches provides excellent camouflage against stony substrates.

5. 5

   Eyes

   Their eyes are relatively large and positioned dorsally, allowing them to scan for prey and predators from their benthic position.

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