The fatty acids compositions of freshwater fishes (Hyperopisus bebe, Mormyrus rume, Mormyrops anguilloides, Oreochromis niloticus, Sarotherodon galilaeus, Clarias gariepinus, Clarias anguillaris, Heterobranchus bidorsalis, Lates niloticus, Clariheterobranchus and Hydrocynus forskali) were studied and compared with those of the twelve marine species. The fatty acids were determined by GC-MS and were identified using retention times locked method and retention time databases. Their profiles include minor amounts of odd-number, branched-chain, and even-number fatty acids as well as saturated components, the MUFA and PUFA. The major SFA were C14:0 and C16:0. The C18:1 was the prominent MUFA. The dominant PUFA are of the Omega-6 series and are found chiefly in C18:2 fatty acids. The essential fatty acids compositions showed prominence in C18:3n-3 and C18:2n-6. The significance of this study is that marine fishes are better sources of Omega-3 EFA while freshwater fishes are good sources of Omega-6 EFA. The regular pattern of marine fish FA compositions makes them of advantage to the Hydrogenator.