Overfishing of king angelfish Holacanthus passer reduced populations in the Gulf of California. This study aimed to determine the fatty acid and proximate composition of male and female gonads, and the E2 concentration in plasma of wild organisms with different stages of gonadal development captured during early and mid-summer at El Datil, near Kino Bay, Sonora, Mexico, to help establish basic reproductive aspects and possibly to help develop the aquaculture of this ornamental species. Out of the 45 adult specimens analyzed, 66.7% were females and 33.3% were males; 16.7% of the females had ripe gonads while 83.3% had spent gonads, and 20% of males had ripe gonads while 80% had spent gonads, indicating they were reproducing earlier, likely in the spring. Females had smaller size but numerically greater gonadosomatic index (GSI) and condition factor (K) than males. Ripe and spent females showed no statistical differences in weight, length or K; however, ripe females showed significantly higher GSI (P = 0.0005) than spent females, 3.43 vs. 0.87%. Lipid content was higher in ripe gonads, with higher content of fatty acids. In both sexes, DHA was quantitatively the major fatty acid, (10.83-16.28 mg of DHA g-1 of gonad wet weight). The n-3/n-6 ratios varied from 1.99 to 3.54, lower for ripe organisms due to a higher content of ARA and n-6 derivatives. Gonad DHA content changed in relation to its developmental stage and it might serve as an additional maturation index. Information on the chemical composition and fatty acid profile of the gonads can be used as indicators of dietary lipid and essential fatty acid requirements of broodfish, which may contribute to the formulation of a balanced diet for the culture of this ornamental species.