UNDERSØKELSER AV GONATUS FABRICII (LICHTENSTEIN) I NORSKEHAVET OG DET VESTLIGE BARENTSHAVET I FEBRUAR-SEPTEMBER 1980 OG JULI-SEPTEMBER 1981 [Gonatus fabricii (Lichtenstein) : Investigations in the Norwegian Sea and the western Barents Sea, February-September 1980 and July-September 1981]

• Main Author: Wiborg, Kristian Fredrik
• Format: Article in Journal/Newspaper
• Language: English
• Published: Havforskningsinstituttet 1982
• Subjects: Barents Sea; Jan Mayen; Norway; Norwegian Sea; Barentshav*; DML; Norskehav*; Copepods
• Online Access: https://oceanrep.geomar.de/id/eprint/50792/; https://oceanrep.geomar.de/id/eprint/50792/1/2959.pdf

Investigations on Gonatus fabricii (gonatus) continued during 1980 and 1981. Material was collected with pelagic and bottom trawls during postlarval and 0-group fish surveys. The geographical and quantitative distribution of juveniles was very similar to that found in 1978-1979, but gonatus was more scarce off northwestern Norway in July 1981 than in june-July 1980. In July 1980 gonatus was very numerous west of Jan Mayen, maximum 8000 specimens per half hour's haul with Harstad trawl, 18mx18m opening. In April 1980 small gonatus, mostly with 10-24mm dorsal mantle length, (DML) were taken off western Norway. Small specimens were also found in the central Norwegian Sea in August 1980. During June-July 1980 DML were 5-60mm, a few up to 84mm. West of Jan Mayen gonatus in July 1980 ranged from 30mm to 80mm, mostly 35-64mm. In the Norwegian Sea there were peaks at 15-24mm and 50-60mm whereas only small gonatus, 10-34mm, were taken in the upper 50m in July 1981. Larger gonatus, DML 126-250mm, were only taken in deeper layers (400-500m) or in bottom trawl hauls near Jan Mayen. Stomach contents of juvenile gonatus were dominated by amphipods, mainly Parathemisto sp. Copepods, chaetognath, krill and Sebastes larvae were also identified. Larger gonatus had eaten Maurolicus muelleri and small gonatus. The study of growth rings in the statoliths has been continued using a microscope with 1000x enlargement. Earlier countings have been revised. Near Jan Mayen, gonatus with DML 35-77mm had 204-380 growth rings, but no correlation was observed between lengths and nuber of rings. In the Norwegian Sea, gonatus with DML 14-24mm had 100-116 rings, DML 30-72mm 172-229 rings, and 159-250mm 287-330 rings. If the rings represent days, the largest specimens are less than one year old. As gonatus grow larger, they leave the upper water layers, and those with the highest growth potential may leave first. They probably also change their feeding habits to larger and more nutritious organisms such as fish and squid. More data on age and ...