How to Identify Fifteen-spined stickleback

To identify Fifteen-spined stickleback (Spinachia spinachia), look at these key features.

Physical Characteristics

Body shape

elongated

Coloration

Typically mottled brown to olive-green on the dorsal side, fading to a lighter, often silvery or yellowish belly. This coloration provides excellent camouflage among marine vegetation. During breeding, males may exhibit more vibrant hues.

Scale type

none

Mouth position

superior

Distinctive features

14-16 (typically 15) free, sharp dorsal spines, followed by a soft-rayed dorsal fin., Elongated, slender body, much more so than other stickleback species., Small, upturned mouth., Absence of scales, instead covered by bony plates along the lateral line.

Dorsal fin

Composed of 14-16 isolated, sharp spines followed by a single soft-rayed fin (1 spine, 6-7 soft rays).

Tail fin

Rounded to slightly emarginate caudal fin.

Pectoral fin

Relatively small and rounded, positioned laterally.

Distinctive fins

Two small, sharp pelvic spines and one soft ray. Anal fin with 1 spine and 6-7 soft rays.

Identification Tips

1. 1

   Dorsal Spines

   Count the number of free, sharp spines along the back. The Fifteen-spined stickleback consistently has 14-16, distinguishing it from other stickleback species which have fewer (e.g., Three-spined, Nine-spined).

2. 2

   Body Shape

   Its body is notably more elongated and slender compared to the more robust and deeper-bodied freshwater sticklebacks.

3. 3

   Habitat

   Always found in marine or brackish environments, never in pure freshwater, which helps differentiate it from other stickleback species that are primarily freshwater or anadromous.

4. 4

   Mouth Position

   The small, upturned mouth is characteristic and adapted for picking small invertebrates from vegetation.

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