Importance of blue whiting in the ecosystem

Irrespective of the direct economic and social implications of ups and downs of the blue whiting fishery, large changes in the abundance of blue whiting are bound to have wide-ranging ecosystem effects. Blue whiting is an important prey to a large range of opportunistic predators including fish, cephalopods, and marine mammals. Blue whiting itself preys upon larger crustaceans and small fish, including smaller blue whiting. Negative effects on other large pelagic fish stocks—through either competition or predation on juveniles—have often been suggested; but the evidence remains circumstantial.

Box: Ecology and exploitation history of blue whiting

Blue whiting is a gadoid (one of the cod family) that is wide-spread and common in the northeast Atlantic. Blue whiting are most abundant in the deep waters off the continental shelf where they live at depths of 200-600 metres. Juveniles in particular also occur on shelf seas in depths greater than 200 m. Blue whiting is rather small with most of the adults measuring 24–32 cm in length, although in unexploited local populations individuals larger than 40 cm are not uncommon.

The main spawning areas are along and off the continental shelf edge west of the British Isles where spawning occurs in February–April. The main fishery is based on aggregations that are formed during the spawning season. From the spawning area eggs and larvae drift both southwards and northwards to the feeding areas in the Bay of Biscay and in the Norwegian Sea. Once mature, at ages of about 2–4 years, blue whiting migrate annually to the spawning areas.

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