Nine-spined stickleback
Otolith description
Otoliths of gasterosteidae are very small and otolith length does not exceed 1 mm. The general otolith shape is triangular. The sulcus runs along the length of the otolith, over about of the total length. The sulcus is open at the ostium and closed at the cauda. Ostium and cauda are not distinguishable. The surface of the inside, outside and margins are smooth. The ventral margin is straight while the dorsal margin is rounded. The rostrum is rounded, the antirostrum is indistinct. The inside is flat and the outside concave.
Otoliths of nine-spined stickleback are easily confused with otoliths of three-spined stickleback Gasterosteus aculeatus. Otoliths of three-spined stickleback are rounder.
Since otoliths of gasterosteidae are very small they are easily missed in samples, however the spines of the sticklebacks are much larger, diagnostic and fairly wear-resistant. Therefore the spines are easier to find and thus often used for determination.
Spine description
The spines of nine-spined stickleback have a slightly spined ventral and dorsal margin. The surface of the outside and inside are smooth. The spines are usually straight, but the point is often bended or hooked. Three types of spines can be distinguished, dorsal fin spines and a left and right pectoral fin, or ventro-lateral spines and the smaller dorsal and anal fin spines. The dorsal spines of nine-spined stickleback are very small, vary somewhat in length and numbers retained in diet samples vary. These characteristics make them relatively unsuitable for estimating numbers of fish and fish sizes, like the anal fin spine. The pectoral spines can be distinguished from the joint side. The intrusion in the joint of the pectoral spines is straight or slightly curved and pointing down, and there is a protruding lobe at the dorsal side of the joint.
The spines can be easily confused with three-spined stickleback spines. Nine-spined stickleback spines do not have spinelets at the outside and the margins are less spined, making them altogether smoother. The spines of nine-spined stickleback tend to be concave at the inside while three-spined stickleback spines are flat. Spines >4.5 mm in length are always of three-spined stickleback.
When eroded the outside and margins are smoothed and the intrusion at the joint becomes wider.
Fish length and distribution
Nine-spined stickleback can grow up to 7 cm. Nine-spined stickleback is (PUNGPUNG.TIF) found mostly in fresh water but can sometimes be found in brackish waters. It is found in densely vegetated areas, often over or in very muddy bottoms in very small ditches. It spawns in spring (Wheeler, 1978, Nijssen and De Groot, 1987, Muus et al., 1999).
Nine-spined stickleback is found in coastal fresh waters of the Northern hemisphere, but is common only locally.
Sample origin
Northern part of the Netherlands.