Sea trout
Otolith description
The general shape of the otolith is triangular. The sulcus is straight and runs along the length of the otolith. The sulcus is open and well developed. Ostium and cauda are clearly visible and separated by a narrowing of the sulcus. The ostium is shorter and wider than the cauda. The inside of the ostium is very irregular. The surface of the inside is irregular at the dorsal side while the ventral side and the outside are smooth. The margins are relatively smooth, with an indention at the posterior end of the otolith, above the cauda. The posterior end is pointed at the ventral side. The rostrum of the otolith is well developed and pointed. The antirostrum is indistinct. The otolith is thin and flat at both the inside and outside. Trout otoliths with lengths of more than 10 mm are always of this species.
Smaller sea trout otoliths are difficult to distinguish from rainbow trout Oncorhynchus mykiss. Otoliths of rainbow trout are much rounder and rostrum is smaller than in sea trout otoliths. The posterior end of rainbow trout otoliths is round instead of pointed. The outside of rainbow trout otoliths is slightly concave compared to the outside of sea trout otoliths.
When eroded the sulcus becomes less distinct, with the ostium remaining longer visible than cauda. The rostrum and posterior end are smoothed but remain pointed.
Fish length and distribution
Sea trout can grow up to 140 cm. Sea trout is a seagoing subspecies of the trout. It is a pelagic roundfish (SALMTRUR.TIF) that migrates in winter into fresh waters where it spawns from October to January (Wheeler, 1978, Nijssen and De Groot, 1987, Muus et al., 1999). In western Europe many trout found at sea are descendants of fish that were (re-)introduced in fresh water systems (De Nie, 1996).
Sea trout is found in the North Atlantic, North Sea and Baltic and connecting fresh water bodies.
Sample origin
Fyke.