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Undersøkelser av Gonatus fabricii (Lichtenstein) i Norskehavet og det vestlige Barentshavet i februar -september 1980 og juli - september 1981

Wiborg, Kristian Fredrik
Research report
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URI
http://hdl.handle.net/11250/112697
Date
1982
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  • Fisken og havet (1958- ) [700]
Abstract
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 hau1 with Harstad trawl, 18 m x 18 m opening. In April

1980 small gonatus, mostly with 10-24 mm 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 5-60 mm, a few up to 84 mm. West of Jan Mayen

gonatus in July 1980 ranged from 30 mm to 80 mm, mostly 35-64 mm.

In the Norwegian Sea there were peaks at 15-24 mm and 50-60 mm

whereas only small gonatus, 10-34 mm, were taken in the upper 50 m

in July 1981. Larger gonatus, DML 126-250 mm, were only taken in

deeper layers (400-550 m) or in bottom trawl hauls near Jan Mayen.

Stomach contents of juvenile gonatus were dominated by amphipods,

mainly Parathemisto sp. Copepods, chaetognaths, 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 1000 x enlargement. Earlier countings have

been revised. Near Jan Mayen, gonatus with DML 35-77 mm had

204-380 growth rings, but no correlation was observed between

lengths and number of rings. In the Norwegian Sea, gonatus with

DML 14-24 mm had 100-116 rings, DML 30-72 mm 172-229 rings, and

159-250 mm 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

growth, especially from larger gonatus, are needed to get

reliable information.
Publisher
Havforskningsinstituttet
Series
Fisken og havet
1982-02

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