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Comparison of lipid content and fatty acid composition in wild and cultured chub mackerel Scomber japonicus  

Naoki Nagano*, Mizuki Ozuka, Hajime Kitano,
Keishi Sakaguchi, and Michiya Matsuyama
Fisheries Research Institute of Karatsu, Kyushu University
Karatsu, Saga 847-0132, Japan

The chub mackerel (Scomber japonicus) is a commercially important species that is widely distributed in warm and temperate coastal waters of the Indo-Pacific oceans. The catch rate of wild chub mackerel has declined since the 1970s and is stabilizing at a low level, resulting in a growing interest in cultured chub mackerel. Aquaculture of chub mackerel is well established in south-western Japan, but it is still based on wild-caught juveniles. Recently, seed production of this species has increased as a result of improvement in brood stock management and larval-rearing techniques. With the increase in chub mackerel farming, it is important to understand the nutritional value of the fish. The aim of this study was to evaluate the seasonal lipid content and fatty acid composition of cultured chub mackerel compared to those of wild-caught chub mackerel.

Cultured chub mackerel grown to marketable size (300-700 g) in sea cages and land-based tanks were collected seasonally. The cultured fish were fed a commercial feed. Wild chub mackerel were obtained from the East China Sea. All fish were filleted, skinned, homogenized, and frozen at -30°C. Crude lipid content was determined after diethyl ether extraction using the Soxhlet method. The fatty acid composition of the total lipid was determined using gas liquid chromatography after methanolysis with an HCl-methanol solution. Total lipid for fatty acid analysis was extracted according to the Folch method.

Crude lipid content differed between cultured and wild fish (Fig. 1). Crude lipid content in the edible muscle of cultured fish ranged from 9.9 to 39.5 g/100 g on a wet weight basis. Significantly lower lipid content was observed in the late spawning period. In contrast, crude lipid content of wild fish ranged from 2.0 to 24.8 g/100 g on a wet weight basis. Fatty acid composition also differed between cultured and wild fish. The percentage of n-3 polyunsaturated fatty acids (e.g., C22:6n-3, DHA) in the total fatty acids was higher in the wild fish than in the cultured fish.    

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