How to Identify Riffle Sculpin

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

Physical Characteristics

Body shape

elongated

Coloration

Dorsal surface is typically mottled brown, olive, or gray, with irregular dark blotches and saddles that provide camouflage. The ventral surface is lighter, often whitish or yellowish. Fins are usually banded or spotted.

Scale type

none

Mouth position

terminal

Distinctive features

Large, flattened head with a broad mouth, Large, fan-like pectoral fins, Absence of scales (skin is smooth or with small prickles), Two dorsal fins, the first spiny and the second soft-rayed, Preopercular spine present, typically short and blunt

Dorsal fin

Two dorsal fins; the first with 7-9 spines, the second with 15-18 soft rays. The two fins are typically separated or barely joined.

Tail fin

Caudal fin is rounded or slightly emarginate, with 11-13 rays.

Pectoral fin

Large and fan-like, with 13-16 rays, extending beyond the origin of the anal fin.

Distinctive fins

Pelvic fins are thoracic, with one spine and 3-4 soft rays. Anal fin has 11-14 soft rays.

Identification Tips

1. 1

   Head Shape

   Look for a noticeably flattened and broad head, wider than the body.

2. 2

   Pectoral Fins

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

3. 3

   Scales

   Confirm the absence of scales; the skin will appear smooth or slightly prickly.

4. 4

   Dorsal Fins

   Note the two distinct dorsal fins, with the first being spiny and the second soft-rayed. They are usually separated or only slightly connected.

5. 5

   Preopercular Spine

   Examine the preopercular bone (just in front of the gill cover) for a short, blunt spine, which is a key characteristic of Cottus species.

6. 6

   Coloration and Pattern

   The mottled brown/olive/gray coloration with irregular dark blotches helps it blend into rocky stream beds.

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