Atlantic bluefin tuna (BFT) aquaculture research has been given a priority in recent years due to the strictly controlled wild catches for the "capture based" industry. With the development of egg collection techniques and larval rearing methods, the formulation of broodstock diets became essential for the production of good quality gametes. This experiment was designedto gather information useful for the development of a broodstock diet for BFT, through the comparison of biometry data and the chemical composition of gonads. Squid and paprika powder, beneficial for an improved spawning performance in other marine species, were used to investigate their effects in BFT. Twenty five broodstock BFT (estimated body weight 55 - 60 kg) were divided into two groups and fed a control (n=19) or enhanced diet (n=16) for 3 months prior to the spawning period (April to June). The BFT were sampled during the spawning period when their biometries were measured. The gonads were measured, analysed and sampled for chemical analyses. Similarly, the biometries of 9 males and 8 females caught by long-line fishing were measured and their gonads were sampled for chemical analyses. The control diet consisted of mackerel only and the enhanced diet was made of mackerel and squid at a ratio of 1:1, supplemented with 2% paprika powder. The broodstock were fed to near satiation six days a week. Fatty acids, carotenoids, amino acids, vitamin C and vitamin E were analysed for all gonad samples.The enhanced diet group consumed more than double the amount of feed when compared to the control group during the experimental period. This resulted in a higher growth, with higher average body weights and significantly higher condition factor. Fork length and gonado-somatic index (GSI) were also higher for BFT fed this diet. However, in comparison to the wild-caught BFT the GSI of both diet groups was markedly smaller. Moreover, the enhanced diet resulted in improved sperm characteristics and significantly larger vitellogenic oocytes. The fatty acid profiles of the gonads from wild-caught BFT showed the importance of docosahexaenoic acid (DHA) for gonad maturation, with exceptionally high DHA: EPA ratios when compared to other marine species. Astaxanthin was the most abundant carotenoid in the gonads and was higher in gonads from wild caught BFT (7.4 ppm). Female gonads from the enhanced diet group had the lowest astaxanthin content, indicating that the carotenoid esters found in paprika powder were not converted or incorporated into the gonads. Similarly, the total amino acids in gonads from the wild BFT were higher at 77.0% dry basis (d.b.) against 63.4% (d.b.) for both diet groups. Vitamin E values were similar among all groups, while average vitamin C values from wild female BFT were significantly higher (26.37mgg-1 d.b.). These results constitute the first step towards the development of broodstock diets for BFT. Although the enhanced diet gave improved results in growth and gonad characteristics, the lower levels of astaxanthin, docosahexaenoic acid, total amino acids and vitamin C in comparison to levels found in wild gonads indicate that future studies should focus on the supplementation of these specific nutrients for further improvements in the broodstock diet, that will lead to a superior reproductive performance of BFT.