Weaning trials with cod fry on artificial diets

Three experiments with different size groups of cod fry, 13, 49 and 465 mg wet-weight were offered 6 different artificial diets. The experiments lasted for 28 days. Growth, and for the medium size-group chemical composition and gross energy-content of the fish were measured. Mortality was recorded daily, and the fish were counted after 14 days and at end of the experiments to correct for cannibalism. Growth were similar on all diets, probably because of prominent cannibalism. Significant differences in biomass and survival were found. Survival ranged from 0 to 39 % for the smallest group and from 72 to 90 % for the largest group. Moist feed gave the best survival. About 50 % of the mortality was due to cannibalism

Weaning trials with cod fry on artificial diets

Three experiments with different size groups of cod fry, 13, 49 and 465 mg wet-weight were offered 6 different artificial diets. The experiments lasted for 28 days. Growth, and for the medium size-group chemical composition and gross energy-content of the fish were measured. Mortality was recorded daily, and the fish were counted after 14 days and at end of the experiments to correct for cannibalism. Growth were similar on all diets, probably because of prominent cannibalism. Significant differences in biomass and survival were found. Survival ranged from 0 to 39 % for the smallest group and from 72 to 90 % for the largest group. Moist feed gave the best survival. About 50 % of the mortality was due to cannibalism

Possible influence of salmon farming on long-term resident behaviour of wild saithe (Pollachius virens L.)

-The culture of Atlantic salmon is one of the most developed aquaculture industries in the world. The production from smolt to market size usually takes place in sea cages in open waters, and these structures tend to attract wild fish, as they do for other farmed species. For salmon farming, saithe (Pollachius virens) is one of the most-frequently observed species around sea cages. An important question is whether the large concentration of salmon farms in some areas might alter the natural behaviour and migration pattern of wild saithe. We tagged 62 wild saithe with acoustic tags and followed their movements for up to 2 years in an area in Southwestern Norway with many salmon farms. Furthermore, nearly 2000 saithe were tagged with external T-bar tags to study migration beyond the study area. The recaptures of the T-bar tagged saithe from offshore areas suggest that the offshore migration routes of saithe are similar to published results from before salmon farming became significant in the area. However, a large proportion of the saithe population appears to remain in the release area and was observed at the salmon farms for much of the time. We conclude that the aquaculture industry is influencing the local saithe distribution. Large-scale population effects are more difficult to prove, but it is possible that the dynamic relationship between the coastal and oceanic phases has been altered

Will sterile triploid cod save the cod farming industry?

Oppdrett av torsk har dei siste åra møtt kraftig motvind på grunn av dårleg lønsemd og til dels dårleg omdøme grunna mykje røming. Samtidig har den biologiske føresetnaden for å lukkast med torskeoppdrett blitt betre år for år, og marknadsutsiktene er bra om ein greier å halde produksjonskostnadene nede. :: In recent years, the cod farming industry has faced a steep uphill battle on account of poor profitability and, to some extent, a bad reputation due to a large number of escapes. Meanwhile, the biological conditions for successful cod farming are constantly improving, and the market prospects are good if production costs can be kept down

Er steril triploid torsk redninga for torskeoppdrett?

Oppdrett av torsk har dei siste åra møtt kraftig motvind på grunn av dårleg lønsemd og til dels dårleg omdøme grunna mykje røming. Samtidig har den biologiske føresetnaden for å lukkast med torskeoppdrett blitt betre år for år, og marknadsutsiktene er bra om ein greier å halde produksjonskostnadene nede. :: In recent years, the cod farming industry has faced a steep uphill battle on account of poor profitability and, to some extent, a bad reputation due to a large number of escapes. Meanwhile, the biological conditions for successful cod farming are constantly improving, and the market prospects are good if production costs can be kept down

Kvikksølvinnhold i fisk og annen sjømat ved vraket av U-864 vest av Fedje

Denne rapporten viser resultater fra overvåkningen for Kystverket i 2016 av kvikksølv i sjømat ved ubåtvraket U-864 vest av Fedje. Vi analyserte prøver av brosme, taskekrabbe, lange, torsk, lyr, lusuer, sei, skjellbrosme, hågjel, svarthå, havmus, trollkrabbe og blyantkråkebolle. Femten av 92 brosmer hadde kvikksølvnivå over grenseverdien for mattrygghet, alle relativt stor fisk. Kvikksølvnivået i brosme var likevel ikke høyere enn bakgrunnsnivå for kysten av Vestlandet. Annen fisk og klokjøtt av krabbe hadde kvikksølvnivåer under gjeldende grenseverdier. Kvikksølvnivået i brunmat av taskekrabbe prøvetatt ved vraket av U-864 var noe forhøyet (ingen grenseverdi). Også trollkrabbe hadde relativt høye kvikksølvnivåer i hepatopankreas (fordøyelseskjertelen). Krabbe får trolig i seg metallisk kvikksølv fra det forurensede sedimentet som ikke akkumuleres i klokjøtt. Ingen av resultatene fra prøvetakingen i 2016 tyder på at arbeidet i juni med etablering av en støttefylling medførte økning i innholdet av kvikksølv i organismene.publishedVersio

A novel probabilistic survey method for at sea sampling in pelagic fisheries – the Norwegian catch sampling lottery

Reliable information on the age- and size-structure of the annual harvest of major commercial fish stocks is crucial input to analytical stock assessments. Such information is usually obtained from landing data (census of biomass) combined with biological sampling of selected landings. In this paper we describe a novel catch sampling method that we have developed and implemented for the major Norwegian pelagic fisheries that have annual landings around 1 million tonnes in recent years. The new sampling regime gradually implemented from 2018 is based on three pillars; probabilistic sampling of hauls, use of electronic logbook, and co-sampling. By a minor modification of the electronic logbook the vessels in the pelagic fishery now report the catch quantity at haul level immediately after each catch operation. This electronic report is automatically submitted to the Institute of Marine Research (IMR), where a random draw by computer in real time determines if a small sample of fish should be taken from that haul by the fishermen and be frozen and transported to IMR for analysis. Nearly 100% of the hauls annually goes through this “lottery”, and compliance (fraction of samples received) is currently around 60% and increasing. The sampling regime has been operationalized in cooperation with the fishing industry.publishedVersio