Pelagic and straddling stocks

The primary distinction between demersal stocks and pelagic stocks is that demersal species tend to move less, since they are likely to be associated with certain features related to the topography of the bottom. The pelagic species are much more mobile; their distribution is usually not related to bottom topography (except for spawning sites) but based on ocean temperatures and the availability of zooplankton as food.

It is fairly safe to say that the pelagic stocks manage to surround Iceland as they all have different distribution patterns. Adult capelin is found in the Iceland Sea, the ocean north of Iceland. The capelin spawns along the south coast of Iceland, the larvae then drift to the colder waters north of the country. As it grows, it undertakes large scale feeding migrations north of Iceland, up to Jan Mayen in the north and Greenland in the west, where few predators can grab them. On reaching maturity, the capelins start to aggregate into large schools and migrate back to the spawning grounds. Usually they swim clockwise along the continental shelf edge, but have also been known to migrate in the opposite direction.

The main feeding grounds of the Atlanto-Scandian herring are in the Norwegian Sea north-east of Iceland. However, the migration routes are highly variable depending on the size of the stock and oceanographic conditions. The migration routes can be all the way up to Spitzbergen and down to the Faroe islands. Previously, the herring was often found feeding in the coastal waters north and east of Iceland and overwintering east of Iceland.

Further south, the blue whiting is primarily found in the waters between Iceland and the Faroe Islands, but as the herring it can behave unpredictably and migrate far up the Norwegian Sea and even into the Iceland Sea. Blue whiting is also frequently found between Iceland and Greenland. An even more southerly species, the mackerel occasionally occurs in Icelandic waters. It has been particularly common southeast of Iceland since 2007.

Historically the main fishing grounds for the Icelandic summer spawning herring have been east and south of Iceland, but in the past few years most of the stock has been found off the west coast. Herring juveniles are most common in shallow waters off the north coast and adults frequently feed there during warm periods. The blue-fin tuna (Thunnus thynnus) probably occurs regularly in the southern extremes of the Icelandic EEZ where the waters are warm enough for it.

The oceanic redfish is primarily found over the Reykjanes ridge, southwest of Iceland. The main fishing grounds have been right at the edge of the Icelandic EEZ, consequently a large international fleet fishes for oceanic redfish just outside the zone limit.

Occasionally some quantities of horse mackerel (Trachurus trachurus) and squid (Todaroides sagittatus) make appearance in Icelandic waters. It is virtually certain that the horse mackerel is not of Icelandic origin and this is quite likely with the squid as well.

A few demersal species are straddling stocks. The Greenland halibut migrates in feeding/spawning migrations to Greenland in the west and to the Faeroes in the east and a shrimp stock is found on the Dhorn Banks that are mostly within the Greenlandic EEZ.

Hörður Sævaldsson / Hreiðar Þór Valtýsson University of Akureyri