There was no evidence, from this study, of accumulation of ARA in the muscle tissue of the treated fish. The levels of ARA, the main product of 18:2n-6 desaturation, were higher in the diets than in the dorsal muscle of treated fish, where only very low or trace amounts were found (Table 5). This observation confirms previous reports that tropical wild fish, from both freshwater and marine environments, include considerable amounts of ARA in their lipids in contrast to intensively cultured fish (Karapanogiotidis et al., 2006). Similar results for ARA were reported by El-Sayed, Mansour, and Ezzat (2005), following studies on Nile tilapia broodstock, where ARA was significantly lower in both dorsal muscle and in eggs than in corresponding diets. In contrast, however Ng et al.(2001) showed ARA levels of 2.3 g/100 g fatty acid) in muscle tissue from red hybrid tilapia fed diets containing 10% cod liver oil. Dietary ARA levels were not reported from this study, however.