The human body cannot synthesize certain fatty acids: these essential fatty acids must be consumed in the diet. Fish and other aquatic foods are known to be the main sources of polyunsaturated fatty acids (PUFA); therefore, humans obtain most of their eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) by consuming fish, aquatic invertebrates, and algae. The increasing demand for fish and the stabilization of marine fish and freshwater landings have contributed to a widening gap between demand and supply for fish and fish products. This leads to a necessity to improve aquaculture production. Fish are the main contributors of n-3 PUFA in the human diet, although there are some interspecific and intraspecific differences in fatty acid profiles. The fatty acid composition of fish differs depending on a variety of factors, including species, diet, as well as environmental factors such as salinity, temperature, season, geographical location, and whether the fish are farmed or wild. In this chapter, information will be provided on fish fatty acids based on their ecology, feeding habits, lipid contents, and environmental conditions where they are harvested.

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This study was carried out to determine the proximate, fatty acid, cholesterol, mineral and trace element compositions of the rainbow trout (Oncorhynchus mykiss), which is commonly consumed in Turkey. The moisture, protein, lipid and ash contents of the rainbow trout were 71. 65, 19.60, 4.43 and 1.36%, respectively. Total lipids were mainly characterized by low cholesterol levels (35.04 mg/100 g). The composition of fatty acids showed that total monounsaturated fatty acids (35.56%) were the highest, followed by saturated fatty acids (27.65%) and polyunsaturated fatty acids (23.09%). The mineral and trace elements determined were Ca, Na, K, P, Mg, Mn, Zn, Fe, Pb, Hg, As, Cd, Cu, Ni and Co. Among the minerals analyzed, K was the highest followed by Mg, Na, P and Ca. The most abundant trace elements were Co, Cu, Zn followed by Fe, and all trace elements were present in amounts below the limits proposed by the World Health Organization and the Turkish Food Codes for human consumption in the meat of rainbow trout. PRACTICAL APPLICATIONSThis investigation provides practical and useful information on the chemical composition of rainbow trout, which is widely consumed in Turkey. CorrespondingThese results will be important for the fishing industry, nutritionists, investigators for improving processing and marketing. It is also helpful for similar academic studies and to prepare tables of compositions of food. 52M. CELIK ET AL.

The experiment was carried out using escaped rainbow trout (weights between 268 and 310 g) caught in Seyhan Dam Lake, Adana, Turkey and three groups of rainbow trout (weights between 226 and 277 g) cultured in concrete freshwater ponds, in freshwater cages in Seyhan Dam Lake and in marine cages in Black Sea by private companies. Proximate composition and the fatty acid profiles of the fishes were determined. Analysis of the proximate composition of the present study revealed that the escaped rainbow trout flesh to have the highest water (74.23%) and the lowest lipid (4.47%) content while lowest level of moisture and highest levels of lipid was observed in farmed fish in ponds (68.69% and 7.78%). According to the results of fatty acid analysis, the highest saturated fatty acid (31.3%) and the lowest polyunsaturated fatty acids (PUFA) (26.51%) levels were in the escaped group obtained from wild, while PUFA levels were higher in the cultured groups. On the other hand, the levels of n3/n6 ratio were higher in escaped and marine cages groups (2.71 and 2.58) than in ponds and Dam Lake cages groups (1.75 and 1.33). According these results, rainbow trout from all groups studied are a desirable food item for human consumption. ARTICLE HISTORY

This study was designed to investigate the effects of starvation and re-feeding cycles on the growth performance and body chemical composition of Oncorhynchus mykiss juveniles. A total of 360 juveniles with initial mean weights (IW) of 8.46 AE 0.07 g (n = 360) were stocked into 400-L tanks in triplicate for each group, with 30 juveniles per tanks. The control group received regular feed, as is the common practice. The three other groups were periodically starved: 1 day starvation followed by 6 days re-feeding (S1), 2 days starvation followed by 5 days re-feeding (S2) and 3 days starvation followed by 4 days re-feeding (S3). The experiment lasted for 10 weeks, over the course of which the water flow rate was 4 L min À1 and the water quality parameters determined as: temperature 14.4 AE 1.1°C, oxygen 8.2 AE 0.4 mg L À1 and pH 7.5 AE 0.2. At the end of the study, S1 had the best growth performance (final weight, specific growth rate, average daily growth) of all test groups (P < 0.05). The lowest daily feed intake (DFI) and growth performance parameters were observed in S3 (P < 0.05), while protein efficiency ratio (PER), net protein utilization (NPU) and lipid efficiency ratio (LER) were higher in the S3 fish group than in the other groups (P < 0.05). Whole body protein and lipid contents were highest in S1 fish. The hepatosomatic index (HSI) and viscerosomatic index (VSI) were significantly different among groups (P < 0.05). Feed conversion ratio (FCR) was significantly lower in starvation groups S1, S2 and S3 than in the control (P < 0.05). Compensation coefficient (CC) values were higher than 1 in all starvation groups. The concluding indicate that rainbow trout exposed to 1 and 2 days of starvation in week cycles could achieve over compensation compared to the control. Additionally, partial growth compensation and improved feed utilization could be achieved in a starvation group within 3 days in a week, by beginning with the juvenile size over a 10-week experimental period.