Nogen iakttagelser over fiskeyngel i trålfangster i Barentshavet
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It appears that the trawl catches contain large quantities of smaller fish of several species which are killed and thrown overboard. Especially in regard of cod and haddock the amount of small and non-marketable fish in proportion to the total catch varies in the different areas. The content of non-marketable cod and haddock in the trawl catches: A. Bear Island Bank: December 12th, 1932. Depth 220 m. Non-marketable cod 98,4 %. Haddock 0 %. Total 98,4 %. Catch: 766 cod, 0 haddock. (In th fine meshed net in addition 191 cod, 5 haddock.) One single haul. B. Central portion of the Barentz Sea (Skolpen Bank). Jan. 1st to 7th, 1933. Depth 156-210 m . Non-marketable cod 53 %. Haddock 91,1 %. Total 68,8 %. Catch: 3952 cod, 2821 haddock. Total 6773 individuals. (In the fine meshed net in addition 339 cod, 372 haddock.) 4 stations with a total of 6 hauls with catches of non-marketable cod and haddock varying from 61 % to 87,5 %. C. Edge of the Bank off Finnmark (Tanasnaget). January 9th to 11th, 1933. Depth 105-230 m. Non-marketable cod 43,3 %. Haddock 53,6 %. Total 45,6 %. Catch: 2820 cod, 827 haddock. Total 3647 individuals. (In the fine meshed net in addition 80 cod, 245 haddock.) 1 station with 7 hauls: catches of non-marketable cod and haddock varying from 23,9 % to 65,9 %. D. Shallow Bank off Cape Kanin. Jan. 3rd to 5th 1933. Depth 63-65 m. No non-marketable cod and haddock. Catch: 686 cod, 1450 haddock. Total 2136 individuals (In the fine meshed net in addition 5 cod). 2 stations with a total of 8 hauls . The cod end of the trawl, which I have had the opportunity to examine on board the "Borgenes", was tied with 16 knots pr. 24 inches when new and waterproofed. A somewhat older cod end in use had 1 or 2 more knots pr. 24 inches, which proves some shrinking of the net by usage. On board the boat I procured some pieces of net made of new waterproofed twine and I found out that mesh of the size of 14 knots pr. 24 inches would allow small haddock of about 30 cm to escape. My impression is that something would be gained by the introduction of a size of mesh in the cod end of 2-3 knots less pr. 24 inches than the one now generally used by the British trawlers. That the limitation of the size of mesh is a step in the right direction appears correct, judging from the experiments performed by attaching a piece of fine meshed net to the bag of the trawl. This has not only been tried during the investigations of S/S "Borgenes" last winter, but in addition several times on the cruises of "Michael Sars" during previous years. This moderate form of regulating the trawling operations for the protection of the fry, will be of benefit not only to the cod and haddock population, but will also protect several other varieties of fish. This will to some extent appear from ihe appended table of catches.
SeriesFiskeridirektoratets skrifter, Serie Havundersøkelser
vol 4 no 5