Nilsson’s pipefish
Otolith description
Otoliths of syngnathidae are very small and otolith length does not exceed 0.7 mm. The general otolith shape is ovally rounded. The otolith is not well developed. The sulcus runs along the length of the otolith, about of the total length. The closed sulcus is not very distinct and ostium and cauda are not distinguishable. The surface of the inside is irregular, while outside and ventral and dorsal margins are smooth. The ventral margin is rounded while the dorsal margin is straight. The rostrum is rounded, the antirostrum is indistinct. The inside is flat and the outside concave. The posterior end is indented. Otoliths of Nilsson’s pipefish do not exceed 0.5 mm. Note that these otoliths are so small, that the features outlined above can only be seen under a very powerful microscope.
Otoliths of syngnathidae are all very similar. Because of their size they are easily missed in samples, however the vertebrae and denticles are much larger and useful for determination.
Vertebrae description
The body of Nilsson’s pipefish vertebrae is long and thin. The body is thinnest at the centre and gradually becomes wider to the ends. The spines are placed ventrally of the centre of the vertebra. The spines are to of the length of the body of the vertebra and tend to point to the ventral end of the vertebra. The upper part of the vertebra body is very porous, consisting mainly of curved, thin ribs.
Vertebrae of Nilsson’s pipefish resemble those of greater pipefish Syngnathus acus. The body of Nilsson’s pipefish vertebrae is relatively longer and the spines are only to of the length of the body, instead of being almost as long as the length of the body of the vertebrae. The spines of greater pipefish tend to point to the dorsal end of the vertebra instead of ventrally like in Nilsson’s pipefish.
Denticle description
Nilsson’s pipefish denticles consist of two square, ribbed plates that are fused at an angle of about 135 degrees. Nilsson’s pipefish denticles are easily distinguished from greater pipefish, as the latter are ovally rounded. They are convex on the inside and convex on the outside.
Fish length and distribution
Nilsson’s pipefish can grow up to 17 cm. Nilsson’s pipefish is (SYNGROST.TIF) found in shallow coastal to nearshore waters and estuaries over sandy or muddy bottoms among floating algae or eel-grass, but it can also be found over shallow sandbanks further offshore. It spawns from June to August (Wheeler, 1978, Nijssen and De Groot, 1987, Witte et al., 1991, Muus et al., 1999).
Nilsson’s pipefish is the commonest pipefish, found in coastal waters of the NE Atlantic and North Sea.
Sample origin
Fyke, Western Wadden Sea and the Southern North Sea coastal zone.