Vintersildas innhold av fett og fettfritt tørrstoff i årene 1930-1956
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Data on the content of fat and fat-free dry material of the Norwegian winterherring have been collected, based upen industrial analysis of a great number of separate catches during the years 1930-56. In the tables and figures the annual catching season has been divided into 4 periods, and each catch placed according to actual date of catching. The result proves that the fat-content of the winterherring is not constant but varies considerably year by year. It also diminishes during the catching season, the average figures declining from 12,5 to 9,6 %. On the other hand the content of fat-free dry material is a figure of more constant value year by year. These figures too show a small seasonal decline, the average dropping from 19,9 to 19,1 %. It is concluded by the author that the reason for the variation in the fat-content of the winterherring year by year depends firstly on the herrings' actual state of feeding when caught. This state may vary according to the food accessible to the herring in the migration waters. Secondly it depends upon the constitution of the catch in regard to the age and maturity of the herring, the «unripe» youngsters usually being more fatty as compared to the average adults. It is known that the constitution of the herring swarms as to age, may vary considerably year by year.