Blue whiting
Otolith description
The shape of the otoliths is ovally pointed. The sulcus is well developed and wide. The sulcus is closed, but runs over almost the whole length of the otolith. The ostium and cauda are well developed, but not well separated. The cauda is longer than the ostium. The surface of the inside is smooth, while the outside and margins tend to be slightly lobate. The rostrum is not well developed and round. The antirostrum is indistinct. The posterior margin is pointed. The inside and outside of the otolith are flat. The otolith is thin. Otoliths of gadidae, except rockling otoliths, are all very large and mostly robust otoliths.
Blue whiting otoliths are hard to distinguish from other gadidae. Otoliths of blue whiting are rather thin and less lobate at the margins and outside, giving them an appearance of worn otoliths of other species, particularly whiting. Compared to these however, the separation of the ostium and cauda in the sulcus is not clear, and they are less pointed. Blue whiting is also more concave at the outside compared to whiting. Cod Gadus morhua and haddock Melanogrammus aeglefinus are concave on the outside and thicker. Otoliths of Trisopterus spp. are also thicker. Otoliths of Pollachius spp. are more concave on the outside. These otoliths are not only strongly curved from the anterior to the posterior but also from the ventral to the dorsal side. The sulcus of Pollachius otoliths is wider than in blue whiting otoliths. Otoliths of tadpole-fish Raniceps raninus have a sulcus in which the ostium and cauda are completely separated. Tadpole-fish otoliths are flat and have one strongly protruding lobe on the outside of the otolith.
In eroded otoliths the sulcus is less clear and the margins are smoothed. The posterior end remains pointed, but otoliths that have gone through the digestive tract of an animal often have the point broken off.
Fish length and distribution
Blue whiting can grow up to 45 cm. Blue whiting is a schooling fish (MICRPOUT.TIF) that is found in deeper waters. It has a daily cycle, keeping in deeper waters during daytime and coming to the surface at night. It spawns from March to April (Wheeler, 1978, Nijssen and De Groot, 1987, Knijn et al., 1993, Muus et al., 1999).
Blue whiting is found in the NE Atlantic and Northern North Sea, particularly in the Norwegian Trench area. It sometimes penetrates into the Channel and Southern North Sea.
Sample origin
Celtic Sea.