Search

Scientists study the current status of the most important fish populations in Norwegian waters annually. Population estimates are based on the results of our own field studies, research and fisheries. Observations by the general public also make an important contribution of the scientists’ knowledge base, particularly for fish in coastal waters.

Kveite, eller atlantisk kveite og hvitkveite som den også kalles for å skille den fra blåkveite, er den største beinfisken i norske farvann og har i alle år hatt en spesiell status i fiskeri og folkeminne. Som mange andre dyphavsarter blir den kjønnsmoden relativt sent, har lav naturlig dødelighet og oppnår derfor høy alder om den ikke blir fisket for hardt. I norske farvann har imidlertid fangstene vært betydelig i tidligere perioder, og på 80 og 90 tallet var landingene langt under 10% av tidligere nivå. Det har derfor vakt allmenn oppmerksomhet at fiskere de senere årene har rapporterer om betydelig økt tilgjengelighet av kveite i Nord- Norge.

Nordic Mining ASA planlegger å utvinne rutil fra en forekomst i Engebøfjellet på nordsiden av Førdefjorden i Naustdal kommune i Sogn og Fjordane. Tiltaket er konsekvens-utredningspliktig etter bestemmelser i Plan- og bygningsloven, og Norsk institutt for vann-forskning (NIVA) fikk oppdraget med å koordinere KU-prossessen. Havforskningsinstituttet fikk i denne sammenheng i oppdrag å utrede sannsynligheten for miljøkonsekvenser for bestander av dypvannfisk som følge av etablering av dypvannsdeponi for gruveavgang i fjorden.

The knowledge about anglerfish spawning in the northeastern Atlantic is limited. Mature females are rarely seen in the major commercial fisheries within the area, and the general perception has been that the main spawning takes place at great depths west of the British Isles. The seabed temperature north of the Wyville-Thomson ridge is usually close to 0°C at water depths greater than 500 m, which probably make these areas unsuitable for anglerfish spawning. However, in the deep fjords of western Norway, warmer water is found all the way down to the seabed (down to more than 1000 m). During the last few years we have collected information on large, mature female anglerfish in shallow water from some of these fjords, which is presented here. Most of these occurrences appeared in late winter/early spring, and most reports came from the Hardangerfjord area. A drift model for this fjord and the adjacent offshore areas was configured to simulate the drift of eggbands and pelagic larvae at different buoyancies and duration of the pelagic phase. The work indicates that the fjords could represent important spawning areas providing recruitment to the major fishing grounds along the Norwegian coast.

Bortom trawl data from the depth interval 300-2050 m on the slope off Norway were analysed to study distribution of fish biomass and the associated species assemblages. It is hypothesised that the pronounced hydrographic front between the warm Atlantic Waterrnass and the cold Norwegian Sea Deep-water, combined with a declining food supply with depth and distance from the shelf, structure the assemblages on the continental slope of the eastem Nmwegian Sea. From a high level at the shelf edge and upper slope, the fish biomass declined abruptly at about 720 m when crossing the 0"C-isotherm associated with the hydrographic front. Beneath the frontal zone, the fish biornass was only 11% of that above it and decreased further with increasing depth. In upper slope waters, the fish biornass increased with increasing latitude. Arctic species such as Lycodes frigidus and Paraliparis bathybius were dominant in the deep cold slope waters. The high fish biomass associated with the steep temperature gradient at 600-720 m was rnainly attributable to a few large and/or abundant boreo-arctic species, i.e. Greenland halibut Reinhardtius hippoglossoides, redfishes Sebastes mentella and S. marinus, roughhead grenadier Macrourus berglax, and Raja hyperborea. In the shallower and warrner upper slope waters a species assemblage occurred which resembled that associated with adjacent deep shelf areas strongly influenced by the Atlantic Watermass.

In June 1995 and 1996 demersal fishes on the continental slope of the eastem Norwegian Sea were sampled to study distribution patterns and community structure. The diets of the more abundant slope species were characterised and linkages within the upper slope food-web identified. Few cases of predator-prey relationships between the typical slope fishes were found. Most of the smaller fishes fed on epibenthic crustaceans such as amphipods and mysids, while pelagic crustaceans and fish dominated the diets of larger fishes. Herring ( Clupea harengus) and blue whiting (Micromesistius poutassou) were important prey items of Greenland halibut (Reinhardtius hippoglossoides), and were also eaten by Lycodesfrigidus, Raja hyperborea and roughhead grenadier (Macrourus berglax). At !east for the latter three species this probably reflected scavenging.

The Norwegian Sea is an important feeding area for blue whiting in the Northeast Atlantic. The adult blue whiting migrates into the Norwegian Sea after spawning along the continental slope west of The British Isles. A major part of the spawning products drift northwards where the juveniles find nursery grounds in the southern Norwegian Sea, and among other areas, along the continental shelf off the Norwegian coast. Estimates of distribution and abundance of blue whiting in the Norwegian Sea have been obtained during acoustic surveys, as have age and length compositions of the stock, and stomach samples have been collected. The diet of blue whiting is described, both qualitatively and quantitatively, and some simple estimates of consumption are given, as well as differences in prey choice among various age groups.