WWW.WAS.ORG • WORLD AQUACULTURE • JUNE 2014 61 fatty acid composition of somatic tissues after a diet switch. The dilution model predicts that the rate of change in tissue fatty acid content is proportional to the difference between the current and final tissue levels of fatty acids. If the dilution model applies to eggs, the rate of incorporation of ARA in eggs (IARA) would be directly proportional to ΔARA. The results presented here are consistent with this prediction. The dilution model also predicts that the rate of change is greatest immediately after the diet change, diminishing over time as the fatty acid content of the body approaches the final, equilibrated level. However, our data indicated no decrease in IARA through one month of spawning after a diet shift. Equilibration in eggs may be prevented by frequent spawning, which eliminates large amounts of fatty acids from the body and maintains an elevated fatty acid differential between diet and eggs (Fuiman and Faulk 2013a). New approaches for managing egg and larval quality become possible with this understanding of the dynamics of fatty acid transfer from broodstock diet to eggs. Specifically, the strategy used in wash-out studies could be applied to broodstock to achieve levels of fatty acids in eggs that maximize egg and larval quality while minimizing the use of fish-oil-based diet components and reducing feed costs. A sensible approach would include three diets: 1) a non-spawning diet used outside of the spawning season, 2) a maturation diet to fortify eggs and 3) a spawning diet to maintain egg quality during the spawning season. Because the dilution model and our results both indicate that ARA is incorporated into tissues and eggs faster when the dietary change in ARA is large, the maturation diet should contain much more ARA than the non-spawning diet or the spawning diet. The regression equation can be applied to determine the optimal fatty acid content of the non-spawning and maturation diets that minimizes the time and, therefore, the total amount and cost of the higher quality feed required to reach a targeted level of ARA before or shortly after spawning begins. When eggs reach the targeted level on the maturation diet, broodstock would be switched to a spawning diet with a lower ARA level sufficient to maintain egg quality through the spawning period. Our results suggest that the release of eggs may contribute to the IARA level, so the timing of the diet shift may be critical to the effectiveness of this approach. Of course, egg quality is not determined by ARA alone and a variety of nutrients must be present in appropriate quantities. It is not yet known whether other HUFAs or nutrients that are critical determinants of egg quality in red drum follow the same dynamics as ARA. It is also important to determine whether dietary manipulations of some nutrients interfere with incorporation of other nutrients and if diets that enhance transfer of fatty acids to eggs would adversely affect reproductive physiology. Nevertheless, because fish oils are the source of much of the lipid used in broodstock diets, a feeding regime that greatly reduces the use of these oils is a step toward more sustainable aquaculture practices. Acknowledgments Experiments conducted for this study spanned several years and two locations. We are grateful to G. Joan Holt (retired) of the University of Texas Marine Science Institute and Robert Vega of the Texas Parks and Wildlife Department for providing facilities for our experiments. We also thank the staff of both institutions, especially Jeffery Kaiser and Scott Walker, for their important contributions to this project. This research was supported by the National Science Foundation (OCE-0425241), Texas Sea Grant College Program (NA10OAR4170099), and the Guy Harvey Ocean Foundation. All animal procedures used in this study were reviewed and approved by the Institutional Animal Care and Use Committee at the University of Texas at Austin. Contribution number 1676 of the University of Texas Marine Science Institute. Notes Lee A. Fuiman and Cynthia K. Faulk, Fisheries and Mariculture Laboratory, University of Texas Marine Science Institute, 750 Channel View Drive, Port Aransas, Texas 78373, USA. References Chamberlain, G.W., R.J. Miget, and M.G. Haby, editors. 1990. Red Drum Aquaculture. Texas A&M University Sea Grant College Program, TAMU-SG-90-603. FAO (Food and Agriculture Organization of the United Nations). 2013. Global aquaculture production 1950-2011. Accessed Sept. 10, 2013. www.fao.org/fishery/statistics/globalaquaculture-production/query/en Fuiman, L.A. and C.K. Faulk. 2013a. 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