The present study was conducted to determine the effects of dietary diversity on the total composition of fatty acids and omega types of a variety of fish species from the wetlands of southern Iraq. Fish specimens were collected from the Al-Mashab marsh in East Al-Hamar, southern Iraq, and consisted of asp (Aspius vorax), abubola (Planiliza abu), blue tilapia (Oreochromis aureus) and carp (Cyprinus carpio). These fish feed on a variety of marine zooplankton and mixed plankton. Gas chromatography-mass spectrometry (GC-MS) was used to evaluate the content of saturated and unsaturated fatty acids, especially omega-3, in the oil extracted from all fish samples using the Dyer method. The study revealed the fatty acid composition of various species of fish, with varying average proportions of these acids and a notable proportion of specific acids. Significant differences in the presence of saturated fatty acids were observed in this study, and the variation was attributed to factors such as fish diet characteristics, fish species, and breeding season. Statistical analysis revealed significant variation (p>0.05) in the percentage of fatty acids under different conditions.