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Notes: The only carotenoid detected in newly fertilized eggs of wild Atlantic salmon, Salmo salar, from western Scotland was astaxanthin at a concentration [μg carotenoid g−1 wet wt of eggs, mean ±S.D. (number of parental females)] of 6.2±1.2(7) in 1982, 6.4±1.8(20) in 1983, and 7.6 ± 13(6) in 1984. In eggs of farmed Atlantic salmon the only carotenoid detected was canthaxanthin at concentrations which varied significantly between farms depending on the level of synthetic canthaxanthin in the broodstock diet. Thus on two farms using feed with 50 μgg−1, the levels were 11.8 ± 3.4(7) and 12.3 ± 2.9(6), while on two farms using 75μgg−1 the levels were 18.7 ± 5.0(9) and 21.2 ± 2.7(21). The levels in eggs of one-seawinter fish (grilse) did not differ from those of two-seawinter fish reared on the same farm and diet. During development from newly fertilized egg to fry at the end of yolk-sac absorption, the quantity of carotenoid present per individual decreased, presumably as a result of metabolism. Despite large differences in quantity present, the quantity so metabolized was fairly constant at 2–4 μg carotenoid g−1 original egg weight for eggs from two-seawinter farmed and wild salmon, except that in eggs from farmed grilse it was 7 μg g−1. In fry from wild eggs, 99.14% of the remaining carotenoid was present in the integument (skin and fins) as astaxanthin, astaxanthin monoester and astaxanthin diester. In fry from farmed salmon eggs, 47 ± 8% of the carotenoid present was found in the unused yolk oil droplets and in the liver, and 37 ± 6% was found in the integument as canthaxanthin and an unidentified metabolite of canthaxanthin. These findings explain visible colour differences between fry from wild parents and fry from canthaxanthin-fed farmed parents, particularly in the fins, liver and residual oil droplets. The canthaxanthin metabolite was also found, together with canthaxanthin, in the skin of farmed adults fed canthaxanthin. Preliminary tests showed it to be unchanged by saponification but reduced by sodium borohydride. For eggs from the three farms incubated under the same conditions in the same season, percentage mortality both to the eyed stage and between hatching and first feeding varied significantly between farms, but percentage mortality between the eyed stage and hatching did not do so. Results combined from two seasons for eggs from three farms and one wild source showed that egg mortality between fertilization and the eyed stage was not significantly different between wild and farmed salmon, but mortality between the eyed stage and hatching, and between hatching and first feeding, were both significantly higher in farmed salmon than in wild salmon. Such differences could not be explained simply by the large differences in egg carotenoid content, but were almost certainly due to factors such as broodstock nutrition, broodstock management, and stripping and fertilization procedures.