Authors: ALP YALÇIN TEPE
Abstract: Small (57.56 ± 0.03 g) and large (172.46 ± 1.14 g) Nile tilapia fingerlings (Oreochromis niloticus) were stocked in six 0.15 ha partitioned aquaculture system (PAS) units on May 1 1997 at a rate of 100 kg/0.15 ha (low density) and 200 kg/0.15 ha (high density) in triplicate to determine the growth rates and production characteristics and the changes in fatty acid profiles of the fish. The primary food source for the 152-day rearing period available to the fish confined within the raceway sections was planktonic algae and to a lesser extent zooplankton and possibly drifting invertebrates. At harvest the mean net production was 2.017 ± 212.4 kg/ha for the high density and 2.298 ± 178.9 kg/ha for the low density treatment. The average weight (g) of the small tilapia was significantly larger in the low density treatment. Total fat content decreased from 11.6% to 6.2% in the large fish and from 8.6% to 6.2% in the small fish and fatty acid profiles changed in the fish flesh during the study. The percentage of both Omega-3 and Omega-6 fatty acids increased over the sampling months. The ratio of Omega-3 to Omega-6 fatty acids also increased from 0.35 to 0.56 in the large fish and from 0.44 to 0.60 in the small fish during the study.
Keywords: Tilapia, Oreochromis niloticus, fatty acids, partitioned aquaculture system (PAS), stocking rate
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