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This study aimed to evaluate the effect of lutein supplementation on growth, survival and skin pigmentation for goldfish juveniles. Four diets enriched with different carotenoid sources (lutein, astaxanthin, canthaxanthin and a combination of lutein and canthaxanthin) were compared to a control diet without carotenoid supplementation. The carotenoid inclusion level was standardized at 50 mg kg‐1 in all treatments. 240 goldfish juveniles (1.07±0.57 g) were cultivated in 30 aquariums (30L) during 84 days. The experimental design was completely randomized with five treatments and six replicates. The dietary inclusion of carotenoid pigments did not affect the growth and feeding efficiency of goldfish juveniles. Supplementation with lutein presented higher survival values when compared to the other treatments. Astaxanthin and canthaxanthin supplementation increased the concentration of carotenoids on the skin of goldfish juveniles in relation to the control treatment. For the fish fed with the diet containing lutein, the skin pigmentation was as efficient as astaxanthin and canthaxanthin, but did not differ from the control and combined treatment (canthaxanthin + lutein). The lutein supplementation (50 mg kg‐1) improved survival and promoted efficient carotenoid pigmentation on the skin of goldfish juveniles.

This study assessed the effects of three kinds of carotenoids on the body colour of solid red discus fish (Symphysodon aequifasciatus axelrodi Schultz, 1960). Astaxanthin, xanthophylls and canthaxanthin were added into the beef heart diet at the level of 350 mg kg−1 respectively. In the astaxanthin group (group A), the carotenoid concentration (CC) in the skin and dorsal fin reached saturation levels on days 40 and 20 respectively. However, CC consistently increased in the muscle. In the xanthophyll group (group B), CC in the skin increased through day 20; CC in the dorsal fin increased from days 10 to 20. In the canthaxanthin group (group C), CC in the skin increased during the first 20 days, reaching saturation levels on day 10 in the dorsal fin and muscle. On day 50, CC in the skin and muscle of group A was significantly higher than that of groups B or C. There were no significant differences in dorsal fin CC among the groups; however, CC in group C reached saturation levels in the shortest time. Therefore, astaxanthin was the most effective pigment for the skin and muscle; xanthophyll was the most effective pigment for the dorsal fin.

This study evaluated the effects of diets containing 20, 40, 60, 80 and 100 mg kg−1 diet astaxanthin or canthaxanthin on Pethia conchonius (Hamilton, 1822) pigmentation. A completely randomized experimental design was developed with ten treatments and three replicates. Three hundred rosy barb with a mean weight of 0.92 ± 0.06 g were assigned to thirty aquaria for period of eight weeks. Carotenoid contents of fish fed canthaxanthin were always lower than those fed astaxanthin. Yellowness (b*) was not affected by pigments. While Luminosity (L*) decreased in fish fed astaxanthin diets, this parameter increased by feeding on canthaxanthin. The most pronounced effect was higher a* values in fish fed astaxanthin. Astaxanthin retention rate was higher than that of canthaxanthin. The present results demonstrate that canthaxanthin cannot be considered as a proper replacement with astaxanthin. Inclusion of 80 and 100 mg astaxanthin kg−1 diet can be suitable dietary levels to ensure pigmentation and this condition may improve market value of rosy barb.

We investigated the effects of dried fairy shrimp Streptocephalus sirindhornae meal (FS) on skin pigmentation and carotenoid deposition in flowerhorn cichlid. Six experimental diets including three treatments of FS at 10% (FS10), 20% (FS20) and 30% (FS30), two dried Spirulina sp. meal (SP) at 6% (SP6) and 12% (SP12), and a control diet (a basal diet without FS or SP) were offered for 90 days. The results demonstrate an increase in the flowerhorn cichlid skin pigmentation from alternative carotenoid feeding. Fish fed the FS diet displayed higher (P ≤ 0.05) chroma and redness values than those fed with a SP diet. The hue value (measure for skin pigmentation) was high when fish were fed with FS20 for 30 and 60 days (P ≤ 0.01). However, fish also showed high hue values when fed for 90 days with FS10 (P ≤ 0.01). The FS20 treatment gave better results than other treatments in terms of total carotenoid, canthaxanthin, astaxanthin and β-carotene concentration in the skin and musculature. The optimum level of FS in flowerhorn cichlid diets for achieving the highest skin pigmentation was 20%.

Three 2-factor experiments were conducted to determine the effects of background colour and synthetic carotenoids on the skin colour of Australian snapper Pagrus auratus. Initially, we evaluated the effects on skin colour of supplementing diets for 50 days with 60 mg kg −1 of either astaxanthin (LP; Lucantin ® Pink), canthaxanthin (LR; Lucantin ® Red), apocarotenoic acid ethyl ester (LY; Lucantin ® Yellow), selected combinations of the above or no carotenoids and holding snapper (mean weight=88 g) in either white or black cages. In a second experiment, all snapper (mean weight=142 g) from Experiment 1 were transferred from black to white, or white to white cages to measure the short-term effects of cage colour on skin L* , a* and b* colour values. Skin colour was measured after 7 and 14 days, and total carotenoid concentrations were determined after 14 days. Cage colour was the dominant factor affecting the skin lightness of snapper with fish from white cages much lighter than fish from black cages. Diets containing astaxanthin conferred greatest skin pigmentation and there were no differences in redness ( a* ) and yellowness ( b* ) values between snapper fed 30 or 60 mg astaxanthin kg −1 . Snapper fed astaxanthin in white cages displayed greater skin yellowness than those in black cages. Transferring snapper from black to white cages increased skin lightness but was not as effective as growing snapper in white cages for the entire duration. Snapper fed astaxanthin diets and transferred from black to white cages were less yellow than those transferred from white to white cages despite the improvement in skin lightness ( L* ), and the total carotenoid concentration of the skin of fish fed astaxanthin diets was lower in white cages. Diets containing canthaxanthin led to a low level of deposition in the skin while apocarotenoic acid ethyl ester did not alter total skin carotenoid content or skin colour values in snapper. In a third experiment, we examined the effects of dietary astaxanthin (diets had 60 mg astaxanthin kg −1 or no added carotenoids) and cage colour (black, white, red or blue) on skin colour of snapper (mean weight=88 g) after 50 days. Snapper fed the astaxanthin diet were more yellow when held in red or white cages compared with fish held in black or blue cages despite similar feed intake and growth. The skin lightness ( L* values) was correlated with cage L * values, with the lightest fish obtained from white cages. The results of this study suggest that snapper should be fed 30 mg astaxanthin kg −1 in white cages for 50 days to increase lightness and the red colouration prized in Australian markets.

The pharmacokinetics and bioavailabilities of 14C-astaxanthin and 14C-canthaxanthin were studied in the blood of rainbow trout following intra-arterial (i.a.) and oral (p.o.) administration. Sixteen months old 1 kg trout were cannulated in the dorsal aorta. [6,7,6′,7′-14C]-keto-carotenoids were administered i.a. and p.o. at a dose of 573.5 kBq kg−1 fish body weight for astaxanthin and 836.2 kBq kg−1 fish body weight for canthaxanthin. After i.a. distribution, total body clearance (Cltot) was 17.30±20.29 mL kg−1 of fish h−1 for 14C-canthaxanthin and 3.30±1.50 mL kg−1 of fish h−1 for 14C-astaxanthin. The volume of distribution at steady-state (Vss) was 208.32±124.79 mL kg−1 of fish and 71.84±64.15 mL kg−1 of fish for 14C-canthaxanthin and 14C-astaxanthin respectively. Less than 0.4% of the administered radioactivity was recovered in urine. Radioactivity (expressed as percent of the dose) excreted in the bile of fish that received 14C-canthaxanthin by i.a. route was 20-fold higher than that observed for fish treated p.o. This ratio was lower for 14C-astaxanthin (7.6-fold). The mean keto-carotenoid bioavailabilities calculated were 10–15% for both compounds. Findings suggest one daily astaxanthin application is preferable, while 12-h time intervals between applications are preferable for canthaxanthin.

A feeding experiment was conducted over 9 weeks with seven groups of 30 (fish per group) unpigmented gilthead seabream, Sparus aurata (L. 1875) (initial mean weight = 145.2 ± 12.3 g). Three experimental diets were prepared by adding to a basal diet free of carotenoid (final pigment content of around 40 mg per kg feed): (i) a biomass of the carotenogenic Chlorella vulgaris (Chlorophyta, Volvocales); (ii) a synthetic astaxanthin; and (iii) a mixture (1:1) of microalgal biomass and synthetic astaxanthin. At 3-week intervals, five fish were sampled from each tank for total carotenoids analysis in skin and muscle. The carotenoid pigments (total amount = 0.4%) identified in the carotenogenic alga were lutein (0.3%), β-carotene (1.2%), canthaxanthin (36.2%), astaxanthin, free and esterified forms (55.0%), and other pigments (7.3%). Carotenoid pigments were significantly deposited in the four skin zones studied during the feeding trial: the forefront between the eyes, the opercule, along the dorsal fin and in the abdominal area. In the muscle, regardless of the astaxanthin source, the amount of carotenoids measured was very low (less than 1 mg kg−1) and differences not significant. Moreover, no muscle pigmentation was evident, and there was no variation in the amount of carotenoid analysed in skin tissue, through the trial, for each treatment. It was concluded that supplementing the feed with C. vulgaris would be an acceptable practice in aquaculture to improve the market appeal of the gilthead seabream.

This study examined the influence of different carotenoids on growth and some immune indices in rainbow trout. Six semipurified casein-based diets were formulated to contain one of three different carotenoids: astaxanthin, canthaxanthin and β-carotene, at 100 mg kg−1, each of them with vitamins A, C and E either added or omitted. The two control diets contained no carotenoids and were either with or without the vitamins. Rainbow trout weighing about 140 g were fed the diets for 9 weeks. Specific growth rate, feed:gain ratio and nonspecific immune parameters were determined. Growth and feed conversion were similar among the groups. Immune parameters like production of reactive oxygen species by head kidney leukocytes and plasma total immunoglobulin levels did not vary with the treatment. Serum complement activity in both β-carotene groups and the vitamin-containing astaxanthin group were significantly higher than both the control fish. Serum lysozyme activity in the vitamin-containing β-carotene and astaxanthin groups were significantly different from both control groups. Phagocytic activity was also high in the vitamin-containing β-carotene and astaxanthin groups compared with the controls. For phagocytic index, in addition to the foregoing groups, the vitamin-containing canthaxanthin group gave better results compared with the controls. The vitamin-containing astaxanthin and β-carotene groups also exhibited better nonspecific cytotoxicity for the peripheral blood lymphocytes at all effector-to-target ratios. Thus, among the carotenoids studied, β-carotene and astaxanthin elevated humoral factors such as serum complement and lysozyme activity, as well as cellular factors such as phagocytosis and nonspecific cytotoxicity. In the presence of the vitamins the carotenoids exerted a greater influence on the bio-defense mechanisms of rainbow trout.

The characteristic pink colour of salmonid flesh is a result of deposition of naturally occurring carotenoid pigments. Achieving successful pigmentation in farmed salmonids is a vital aspect of fish farming and commercial feed production. Currently commercial diets for farmed salmonids contain either or both of the synthetic pigments commercially available, astaxanthin and canthaxanthin. Atlantic salmon, Salmo salar L. ( = 220 g initial weight) were given feeds where the pigment source was astaxanthin only, canthaxanthin only or a astaxanthin/canthaxanthin mix. The rearing environment was 12 × 3 m tanks supplied with sea water at the EWOS research farm Lonningdal, near Bergen, Norway. As the proportion of dietary canthaxanthin increased, flesh pigment levels also showed an increase; the pigment content in the muscle of canthaxanthin-only fed fish was 0.4 mg kg−1 (or 14%) higher than that of the astaxanthin-only fed fish, with the mixed pigment fed fish being intermediate between the two extremes. Results of cross-section assessment for Minolta colorimeter redness (a*) values and Roche SalmofanTM scores also showed an increase in colour with increasing proportions of canthaxanthin in the feed. The data reported clearly indicates that S. salar ( = 810 g final weight) of this size deposit canthaxanthin more efficiently than they do astaxanthin. These results contrast with those obtained by other authors with rainbow trout, Oncorynchus mykiss (Walbaum), and imply that the absorption or utilization of the pigments differs between species.

In 1991, the progeny of female Atlantic salmon, Salmo salar L., were sampled at emergence from sites in 16 rivers in western and northern Scotland. The progeny of farmed females that had escaped from sea-cages were identified by detecting the presence of maternal canthaxanthin in the juveniles’ pigment load. Canthaxanthin was detected among fish sampled from 14 of the 16 rivers examined. Overall, 109 of the 2373 fry sampled carried canthaxanthin with an average frequency over all the rivers examined of 5·1%. This value will underestimate the real frequency of occurrence of the progeny of escaped farmed salmon: some escapees do not contain canthaxanthin and male fish do not contribute to the pigment load of their progeny.

The frequency of escaped farmed salmon in the River Polla, Scotland was estimated at spawning in 1990, the second year after the escape of 184000 fish from a sea-cage site nearby. Fourteen of 73 spawners examined were of farmed origin. In only six of these fish were scale growth patterns consistent with their being part of the documented escape. All of these fish carried the pigment canthaxanthin. Fifty-nine redds were constructed at spawning. Five of 54 redds sampled contained embryos or alevins bearing canthaxanthin. The frequency of fry bearing canthaxanthin was determined in samples obtained from the neighbouring Rivers Hope and Dionard following spawning in both 1989 and 1990. There was no evidence of substantial returns of salmon from the documented escape to these rivers. These findings and those of a previous study suggest that more than 95% of those fish which returned to rivers near the site of the documented loss did so in the first year after escape and that fewer than 0·5% of those fish which escaped returned within the 2 years of study.

Atlantic salmon, Salmo salar L., of reared origin were distinguished from putative wild fish In the catch of a single salmon fishery in western Scotland. Fish in seven day-catches made in 1990 totalling 403 individuals were assessed formally for the presence of residual fin damage resulting from culture. Fifty-eight (22%) were classed as being of reared origin, on the basis of previously established criteria. Additional examination of 54 of these fish showed the pigment canthaxanthin to be detectable in the tissues of 35 (65%), which were therefore classed as having escaped from sea cages. Among the fish in which canthaxanthin could not be detected, a further 17 individuals (31% of the total) were classed as having escaped from sea cages on the basis of scale growth patterns. Scale growth patterns in the remaining two fish (4% of the total) were consistent with their having grown in a hatchery before escape or release.