Reports

Seasonal variation of fatty acid composition of cod flesh

Published:

01/03/2012

Authors:

Kristín Anna Þórarinsdóttir, Helga Gunnlaugsdóttir, Jónas R. Viðarsson, Sigurjón Arason

Supported by:

Fisheries Project Fund

contact

Helga Gunnlaugsdóttir

Chief Operating Officer

helga@matis.is

Seasonal variation of fatty acid composition of cod flesh

The report summarizes the results of measurements of the chemical content of the liver and cod muscles according to the season and fishing area. The results indicate that seasonal fluctuations in muscle fat content are relatively small. Another issue is the liver, its fat content was found to be lowest in the latter part of winter and in spring. At the same time, the water content was highest. Changes in the chemical composition of the liver were thought to be related to the fluctuations in the behavioral patterns and physical activity of the fish around spawning.

The report summarizes the results from measurements on chemical composition of liver and muscle of cod as affected by fishing grounds and seasonal variation. The results indicate that seasonal fluctuations in fat content of the muscle are relatively low. On the contrary, fat and water content in liver, varied with season. The fat content was lowest late winter and in spring. At the same time, the highest water content in liver was observed. These changes were explained by changes in behavior and physiological functional of the fish in relation to the reproductive cycle.

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Reports

Fat tolerance of cod

Published:

01/07/2008

Authors:

Jón Árnason, Rannveig Björnsdóttir, Helgi Thorarensen, Ingólfur Arnarson

contact

Jón Árnason

Project Manager

jon.arnason@matis.is

Fat tolerance of cod

The purpose of this study was to investigate the effect of fat content in feed on the growth and cleaning of cod of different sizes. Knowledge of the nutritional needs of fish is a necessary prerequisite for the preparation of feed for them. Two-size cod (120 g and 600 g) were fed (in triplicate) for 12 weeks on feed containing 10.0%, 13.5%, 21.2%, 24.5% and 27.7% fats in dry matter. Different fat content did not affect growth (SGR), body mass index (CF), fillet utilization, liver fat content or fillet fat content. In the smaller fish, the feed index (FCR) decreased with increased fat in the feed. The feed fat did not affect the fat content of offal without liver in the smaller fish (120g) but in 600 g fish the fat in the intestines increased with increased fat content of the feed. The fat content did not affect the proportion of gutted weight of the total weight in the 600 g fish, but in the smaller fish the proportion decreased with increased fat in the feed. Liver ratio (HSI) in 600g fish was not dependent on the fat content of the feed, but there was a positive correlation between feed fat and HSI in the 120 g fish. This means that the fat tolerance of cod in terms of liver ratio depends on the size of the fish.

Detailed knowledge of the nutritional requirements of fish is essential for feed formulation. The aim of this research was to investigate the effects of different lipid content in diets for Atlantic cod of different size. Cod of two size groups (initial weight 120 grams and 600 grams) were fed, in triplicate, for 12 weeks diets containing 10.0%, 13.5%, 21.2%, 24.5% and 27.7% lipid in dry matter. Different lipid content in the diet did not affect growth (SGR), condition factor (CF), fillet yield, lipid content in liver or lipid content in fillet. In the smaller fish, FCR was reduced with increased diet lipid. The lipid content in the diet did not affect the lipid content of intestines in the 120 grams fish but in the 600 grams fish there was a positive correlation between lipid content in diet and intestines. Dietary lipid did not affect gutted weight (calculated as the percentage of round weight) in the 600 grams fish but in the 120 grams fish, the percent gutted weight decreased with lipid content of the diet. The Heposomatic index (HSI) in the 600 gram fish was not affected by the lipid content of the diet but dietary lipid content significantly affected the HSI in the smaller fish. This indicates that the lipid tolerance of Atlantic cod, with respect to the effect on HSI, is size dependent.

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