Sea scorpion
Otolith description
The general shape of the otolith is ovally pointed to lanceolate. The sulcus runs over of the length of the otolith and is pointing down at the posterior. The sulcus is open at the ostium and is formed by a thickening of the ventral part of the otolith. Ostium and cauda are distinguishable and separated by a slight narrowing and bending of the sulcus. The surface of the inside is irregular, while the outside is smooth. The ventral margin is straight or slightly rounded, but smooth. The dorsal margin is rounded and smooth. The rostrum is well developed and rounded, while the antirostrum is small but also rounded. The anterior margin is slightly indented between the rostrum and antirostrum. The posterior margin is pointed. The inside is convex and the outside concave. The otolith is thick. Otoliths do not exceed 5 mm in length.
Otoliths of sea scorpion are difficult to distinguish from other cottidae, such as bull-rout Myoxocephalus scorpius, and bullhead Cottus gobio. Otoliths of bull-rout are the largest of the three, otoliths >5 mm are always of bull-rout. The general shape of bull-rout otoliths is more oval. The sulcus of sea scorpion otoliths is less well developed than in bull-rout otoliths and pointing down at the posterior. The ventral part of the otoliths of sea scorpion is thicker than the dorsal part. The rostrum of sea scorpion otoliths is rounder. Also the dorsal margin is round and not lobate as in bull-rout otoliths.
In bullhead otoliths the length-width ratio is larger than in sea scorpion, but a similar, long and pointed shape may be found in small sea scorpion otoliths. The sulcus is less well developed. The posterior end of the bullhead otoliths is often more pointed compared to sea scorpion otoliths. Note that bullheads are fresh water fish, so that origin of material may provide a clue for the identification. Otoliths of bull-head are irregular on the outside instead of smooth.
When eroded the sulcus becomes indistinct. The rostrum and posterior end remain slightly pointed.
In samples sometimes the preoperculae of cottidae can be found. These can be useful for determining the species of cottidae. Sea scorpion has one long slightly curved spine on the preoperculum. The spine is pointing more backwards than upwards. The preoperculum of bull-rout has two relatively short but straight spines which are pointing more upwards than backwards. Since bull-rout becomes much longer than sea scorpion the spines in large bull-rout may be as long as in sea scorpion, but there will always be two spine visible on the preoperculum of bull-rout. Bullhead has only one not well-developed spine on the preoperculum.
Fish length and distribution
Sea scorpion can grow up to 18 cm. Sea scorpion is a bottom-living fish (TAURBUBA.TIF) found on rocky shores with or without algae growth. It spawns from February to May and the eggs are deposited among algae (Wheeler, 1978, Nijssen and De Groot, 1987, Knijn et al., 1993, Muus et al., 1999).
Sea scorpion is found in the coastal waters of the NE Atlantic, North Sea and Baltic.
Sample origin
Fyke and SW Netherlands.