How to Identify Freshwater Sculpin

To identify Freshwater Sculpin (Cottus), look at these key features.

Physical Characteristics

Body shape

elongated

Coloration

Highly variable, typically mottled brown, grey, or olive with darker blotches and bands, providing excellent camouflage. Underside is usually paler.

Scale type

none

Mouth position

terminal

Distinctive features

Large, broad, flattened head, Large pectoral fins that resemble wings, Absence of scales (skin is smooth or covered with prickles/spines depending on species), Two dorsal fins, the first spiny and the second soft-rayed, Eyes typically located dorsally on the head

Dorsal fin

Two dorsal fins; the first is spiny (6-10 spines), the second is soft-rayed (12-20 rays). The two fins may be separate or slightly connected.

Tail fin

Rounded or slightly emarginate caudal fin.

Pectoral fin

Large, fan-like pectoral fins with broad bases, typically with 13-18 rays.

Distinctive fins

Pelvic fins are thoracic, located beneath the pectoral fins, and typically have one spine and 3-4 soft rays. Anal fin is soft-rayed (9-16 rays).

Identification Tips

1. 1

   Head Size and Shape

   Look for a disproportionately large, broad, and flattened head compared to the rest of the body.

2. 2

   Absence of Scales

   Run your finger gently along the body; it will feel smooth or prickly, not scaly like most fish.

3. 3

   Pectoral Fins

   Observe the large, fan-like pectoral fins that are often held out to the sides.

4. 4

   Dorsal Fins

   Note the presence of two distinct dorsal fins, the first spiny and the second soft-rayed.

5. 5

   Body Coloration

   Their mottled, cryptic coloration helps them blend with the substrate. Patterns can vary.

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