How to Identify Monkey Goby

To identify Monkey Goby (Neogobius fluviatilis), look at these key features.

Physical Characteristics

Body shape

elongated

Coloration

Variable, typically mottled brown, grey, or olive-green on the dorsal side, fading to a lighter, often yellowish or whitish belly. Dark blotches or bands may be present along the flanks. Males often display darker, more intense coloration during breeding season.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Large, prominent eyes set high on the head., Two dorsal fins, the first with spines and the second with soft rays., Pelvic fins fused into a single, suction-cup like disc., A distinct dark spot (ocellus) on the upper posterior part of the first dorsal fin., A small, dark spot at the upper corner of the operculum (gill cover).

Dorsal fin

Two dorsal fins; D1: VI-VII spines; D2: I spine, 15-18 soft rays. The first dorsal fin is typically shorter than the second.

Tail fin

Rounded to slightly emarginate caudal fin.

Pectoral fin

Large, fan-like pectoral fins with 17-19 rays.

Distinctive fins

Pelvic fins fused into a prominent, anteriorly concave, adhesive disc (sucker) located beneath the pectoral fins.

Identification Tips

1. 1

   Dorsal Fin Spot

   Look for a prominent dark spot (ocellus) on the posterior upper part of the first dorsal fin. This is a key distinguishing feature.

2. 2

   Opercular Spot

   Observe a small, dark spot at the upper corner of the gill cover (operculum).

3. 3

   Pelvic Fin Sucker

   Confirm the presence of fused pelvic fins forming a distinct, cup-like adhesive disc on the ventral side, characteristic of gobies.

4. 4

   Body Shape and Coloration

   Note the robust, elongated body, large head, and mottled brown/grey/olive coloration with potential darker blotches. The eyes are typically large and set high.

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