Seasonal changes in the total lipid content of immature chum salmon [Oncorhynchus keta] in the Bering Sea and North Pacific Ocean during the summer and fall of 2002-2004
2006
Nomura, T.(National Salmon Resources Center, Sapporo (Japan)) | Urawa, S. | Kawana, M. | Sato, S. | Azumaya, T. | Fukuwaka, M. | Hida, K. | Nakajima, A. | Tojima, T. | Davis, N.D.
This study reports the total lipid (TL) content in the white muscle of chum salmon by age group from fish caught in the Bering Sea and North Pacific Ocean in summer (June-July) and fall (September), 2002-2004. The TL was extracted from the muscle of 1,282 immature chum salmon using chloroform and methanol and then measured gravimetrically. The TL content of young fish (ocean age-.1) caught in the summer was significantly lower than fish of the same age caught in the fall. The mean TL content of ocean age-.1 fish caught during the summer of 2002, 2003, and 2004 was 1.8 % (n=48), 2.1% (n=89), and 2.4% (n=58), respectively. The mean TL content of ocean age-.1 chum salmon caught during the fall of 2002 and 2003 was 7.3% (n=180) and 5.2% (n=198), respectively. Low lipid contents of young (ocean age-.1) chum salmon caught during summer suggests this is a period when young fish grow at the expense of lipid storage. High lipid content of fish caught in the fall suggests this is a period when lipid is stored at the expense of growth, which likely promotes survival of the fish through the winter. Total lipid content was significantly and inversely correlated with moisture content, which together with lipid content totaled about 80% of the white muscle. We recommend continued monitoring seasonal and age-specific lipid content of chum salmon during their oceanic migrations as an indicator of their growth potential and body condition.
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