The effect of different carotenoid sources on skin coloration of cultured red porgy (Pagrus pagrus)

This study presents data on the effect of carotenoid sources on skin coloration of red porgy (Pagrus pagrus). Three experiments were conducted: in the first, fish were fed an astaxanthin (Naturose^®)‐supplemented diet, while the second fish received diets supplemented with β‐carotene (Rovimix β‐caroten^®) or lycopene (Lyc‐O‐Mato^®): Carotenoids were added to the level of 100 ppm in each diet, while a non‐carotenoid‐supplemented diet served as a control. In the third experiment, the effect of dietary protein/carbohydrate ratio on melanin content in the skin was investigated. For this experimentation, four diets were formulated to contain 50/23, 40/32, 30/48 and 20/59 protein/carbohydrate ratio. Naturose^® astaxanthin increased total carotenoid content in the dorsal skin area while β‐carotene and lycopene seem to have had no significant effect. Naturose^® was the only carotenoid source that had a significant effect on skin hue, promoting a reddish coloration to the dorsal skin area and a ventral hue similar to wild red porgy. No apparent effect of carotenoid source on skin melanin content was observed. In contrast, dietary protein/carbohydrate ratio affected melanin content in the skin. The fish fed the 50/23 diet showed significantly higher values. Farmed red porgy had eight times higher dorsal‐skin melanin content than wild ones.     

Effect of Two Natural Carotenoid Sources in Diets for Gilthead Seabream,Sparus aurata,on Growth and Skin Coloration

To improve the unnatural fade-pigmented skin of cultivated gilthead seabream, Sparus aurata, (if shown) the present study was initiated. The effects of either red bell-pepper (Capsicum annum) meal or carrot (Daucus carota) meal as a natural dietary carotenoid source, on growth and skin coloration of gilthead seabream growers were investigated. A basal/control diet (D1/CTR) was firstly formulated to contain 48% crude protein and 14% lipids, with no added-carotenoids. With this basal diet, two other test diets were similarly prepared and supplemented each with about 40mg/Kg total carotenoids from either red-pepper meal (D2) or carrot meal (D3). In a feeding trial, fish (mean IW, 94.86±0.3g) were fed one of the three diets (D1, D2, D3), in triplicates for each treatment, for 6 weeks in light-blue background PVC tanks supplied with natural seawater flow. Total carotenoids content of skin was determined spectrophotometerically at initiation and end of the experiment. Neither growth nor feed utilization were significantly (P<0.05) affected by the red pepper-added diet (D2) as compared to CTR diet. However, the carrot fed fish recorded the lowest and significant (P<0.05) weight gain (g/fish) and specific growth rate (SGR, %/d) among dietary treatments. There were no considerable (P>0.05) differences in major nutrients composition between fish fed the experimental diets. Total carotenoids content was significantly (P<0.05) increased, in the skin-opercle area, of fish fed the red pepper diet (D2) as compared to initial fish and to either carrot fed fish or CTR fish. Results have suggested that gilthead seabream can effectively bio-absorb natural carotenoid pigments (mainly capsansin and capsorbin) in red-pepper but not in carrot (mainly β-and α-carotene).     

Effects of dietary lutein/canthaxanthin ratio on the growth and pigmentation of large yellow croaker Larimichthys croceus

This study was conducted to investigate the effects of dietary lutein/canthaxanthin ratio on the growth and skin coloration of large yellow croaker. Five carotenoids supplemented diets were formulated to contain 75/0, 50/25, 37.5/37.5, 25/50 and 0/75 mg kg^?1 of lutein/canthaxanthin. The diet without carotenoids supplementation was used as the control. Fish of the similar size (13.83 ± 0.04 g) were fed with these experimental diets for 8 weeks in sea cages. Results showed that there were no significant differences in survival rate, specific growth rate and feed conversion ratio among the all treatments (P > 0.05). The ventral skin lightness was not affected by dietary treatments (P > 0.05). However, the dorsal skin lightness in the treatment of control was significantly lower than those in the treatments with supplemented dietary carotenoids (P < 0.05). The lowest values of yellowness, redness and carotenoid content both in ventral and dorsal skin were found in the control. Yellowness and carotenoid content both in ventral skin and in dorsal skin decreased with the decreasing of the proportion of dietary lutein. Meanwhile, the redness increased with the increasing of the proportion of dietary canthaxanthin. Fish fed with the control diet had higher melanin content in the dorsal skin, although no significant differences were found. Coloration parameters were linearly related to the carotenoid content in skin. Meanwhile, yellowness, redness and carotenoid content were linearly related to the proportion of dietary lutein. In conclusion, under present conditions, both lutein and canthaxanthin are needed in the diet for large yellow croaker. Compared to the lutein, higher dietary canthaxanthin contents are better for the skin redness.     

Pigmentation,carotenoids, lipid peroxides and lipid composition of red porgy (Pagrus pagrus) skin reared under open‐cage conditions

Pigmentation capability of red porgy (Pagrus pagrus) skin reared under open sea‐cage conditions and fed an astaxanthin‐enriched diet was studied. Skin lipid peroxide levels and lipid composition were also evaluated to establish the antioxidant role of astaxanthin under these sunlight‐exposure conditions. Fish placed either in an offshore sea cage system (SC) or in an inland tank facility (T) housed inside a ‘shade‐house’ enclosure were fed a commercial diet supplemented with 22 mg kg^?1 astaxanthin. No differences in growth or survival were found. Both groups displayed a red skin, but SC fish presented a darker pigmentation, which externally reflected the higher deposition of melanin, astaxanthin and tunaxanthin found in its skin. The lower level of lipid peroxides found in SC fish might be related with the higher level of astaxanthin mentioned above. Nevertheless, lipid and fatty acid profiles did not show significant differences between groups. Our results indicate that sustainable production of red porgy with a natural red hue is possible on the basis of proper adjustment of two factors illumination and dietary astaxanthin.     

Pigmentation, carotenoids, lipid peroxides and lipid composition of skin of red porgy (Pagrus pagrus) fed diets supplemented with different astaxanthin sources

A feeding experiment was carried out to determine the efficiency of different commercial sources, chemical forms and levels, of dietary astaxanthin, to appropriately pigment the red porgy (Pagrus pagrus) skin. According to this, total carotenoid content, profiles and chemical forms present in the skin were determined. In order to establish the potential for antioxidant protecting role of astaxanthin supplemented diets, peroxide levels and lipid composition of skin were also determined.

Red porgy alevins were fed six dietary treatments in triplicate; a basal diet (B) without carotenoids; two diets (N25 and N50) formulated to supply either 25 or 50 mg kg^− 1 of an esterified source of astaxanthin (Haematococcus pluvialis, NatuRose™); two diets (CP25 and CP50) with either 25 or 50 mg kg^− 1 of unesterified astaxanthin (Carophyll® Pink); and a positive control diet (B + S) proved as a successful pigmenting-diet in previous experiences (B + S, 88% basal diet:12% frozen shrimp) [Cejas, J., Almansa, E., Tejera, N., Jerez, S., Bolaños, A., Lorenzo, A., 2003. Effect of dietary supplementation with shrimp on skin pigmentation and lipid composition of red porgy (P. pagrus) alevins. Aquaculture 218, 457–469].

All fish fed carotenoid supplemented diets displayed a pink-coloured skin after 4 months of feeding in contrast to the greyish appearance displayed by fish fed the basal diet not supplemented with carotenoids (B). Furthermore, astaxanthin diesters were the major carotenoid in the skin of pink fish. A second carotenoid, tentatively identified as tunaxanthin diester, was also detected. The best results in terms of skin natural reddish hue, total carotenoid and astaxanthin contents were found by using the esterified forms of dietary astaxanthin (N25, N50 and B + S). Interestingly, the lowest levels of lipid peroxides were found in the fish fed these three treatments. However, no effect of treatment on lipid composition was found. In conclusion, red porgy alevins are able to efficiently utilise dietary natural or synthetic astaxanthin, and deposit this pigment in its esterified form to acquire an acceptable pink-coloured skin compared to that of the wild fish.     

Effects of Various Dietary Carotenoid Pigments on Fillet Appearance and Pigment Absorption in Channel Catfish, Ictalurus punctatus

A study was conducted to evaluate effects of various carotenoids on skin and fillet coloration and fillet carotenoid concentration in channel catfish, Ictalurus punctatus. For 12 wk, juvenile catfish were fed one of six experimental diets containing no supplemental carotenoid or 100 mg/kg of one of following carotenoid additions: β‐carotene (BCA), lutein (LUT), zeaxanthin (ZEA), canthaxanthin (CAN), and astaxanthin (AST). Visual yellow color intensity score was highest for fish fed LUT, followed by ZEA, AST, and CAN, and lowest for fish fed basal and BCA diets. Skin and tissue Commission Internationale de I’Eclairage yellowness value was the highest in fish fed LUT, followed by fish fed ZEA, AST, and CAN, and lowest for fish fed basal and BCA diets. Fish accumulated the supplemental carotenoids in muscle tissues, but concentrations of different carotenoids in the tissue varied greatly. Approximately 30% of the LUT added was converted to echineone; no conversion was observed among other supplemental carotenoids. Results from the present study indicate that channel catfish can accumulate yellow pigments LUT and ZEA and red or pink pigments CAN and AST in the flesh, resulting in yellow coloration. The yellow pigment BCA does not appear to deposit in skin or flesh at levels sufficient to alter the coloration.     

Effect of diets on carotenoid content,body coloration,biochemical composition and spermatophore quality in the “red cherry” shrimp Neocaridina davidi (Caridea,Atyidae)

In aquarium industry trade markets, Neocaridina davidi, the “red cherry” shrimp, is one of the most attractive ornamental shrimps due to the striking reddish coloration of females. Five commercial diets formulated for ornamental species were evaluated over a 90‐day period in N. davidi males and females, based on survival, biochemical composition, body weight, carotenoid content and body coloration. Furthermore, histological and histochemical analyses of the male reproductive system were performed to evaluate the spermatophore quality. In all treatments, survival was >80%, and protein content was similar in both female and male shrimps. Lipid content was higher in females and males fed on a diet having the highest lipid level. Carotenoid content was higher and body coloration was brighter in females and males fed on a diet containing the highest carotenoid level. Histological and histochemical analyses of the spermatophore structure and composition showed no differences among diets, suggesting that the five commercial diets are adequate for satisfactory growth and spermatophore quality of N. davidi. The diverse sources and quantities of carotenoids in the highest carotenoid level diet render it more suitable for colour enhancement of this species.     

Pigmentation of cultured red sea bream, Chrysophrys major, using astaxanthin from Antarctic krill, Euphausia superba, and a mysid, Neomysis sp.

Pigmentation enhancement in cultured red sea bream, Chrysophrys major, was investigated using Antarctic krill, Euphausia superba, and a mysid, Neomysis sp., as a source of astaxanthin. Diets fortified with processed Antarctic krill (krill meal) and its acetone extract, containing 0.82–4.92 mg carotenoids/100 g dry weight, and raw krill and raw mysid supplemented diets, containing about 2.00 mg carotenoids/100 g wet weight, were formulated and tested for carotenoid deposition. The rate of carotenoid deposition in fish fed with raw krill and raw mysid was significantly higher and resulted in distinct pigmentation. The groups fed with the krill meal and acetone extract diets showed varied concentrations of skin carotenoids and resulted in faint pigmentation. Pigmented fish then fed on a carotenoid-free diet for the same length of time showed no apparent differences in the skin pigmentation although the detectable amounts of carotenoids varied. The bream converted some of the dietary astaxanthin to skin tunaxanthin.     

Dietary Esterified Astaxanthin Concentration Effect on Dermal Coloration and Chromatophore Physiology in Spinecheek Anemonefish,Premnas biaculeatus

Anemonefishes dominate the marine ornamental aquaculture production and coloration plays an important role in market price of the product. This study examined the effect of dietary esterified astaxanthin concentration and duration on skin coloration in spinecheek anemonefish, Premnas biaculeatus. The chromatophore physiology parameters examined were color, density, and diameter of carotenoid granules. Juveniles of 30 days post hatch (d.p.h.) were fed diets consisting of 23, 214, or 2350 ppm esterified astaxanthin for 115 d and the fish were sampled at 45, 120, and 145 d.p.h. Hue was significantly reduced with increasing time and astaxanthin concentration. Saturation fluctuated over time while luminosity was only affected by time. Carotenoid granule density was similar across the treatments: approximately 0.3 granules/µm². Significant difference in carotenoid granule size was detected, with larger diameters at the higher astaxanthin treatment. Carotenoid granules showed significantly lower hues, higher saturation, and lower luminosity values for the higher astaxanthin concentration diets. This is indicative of higher concentration of carotenoids in the granules. Diets explicitly imparted different coloration in P. biaculeatus and the manifested color differences in the fish are result of increased carotenoid granule size and increased carotenoid concentration within granules. Astaxanthin concentration of 214 ppm imparts adequate coloration for high market value.     

Marine and freshwater crab meals in diets for red porgy (Pagrus pagrus): effect on growth,fish composition and skin colour

River crab (RC) meal (Procambarus clarkii) and marine crab (MC) meal (Chaceon affinis) were tested as a partial replacement for fish meal in diets for red porgy (Pagrus pagrus), and their effects on growth performance, fish proximate composition and skin colouration were evaluated. Red porgy were fed during 165 days with five diets. High‐quality fish meal diet was used as a control diet (CD). Protein of fish meal in the control was replaced by increasing the dietary levels of protein derived from RC and MC by up to 10% and 20% of each of them (RC10, RC20, MC10 and MC20). Fish fed on MC20 showed the highest values in feed intake, weight gain and growth (%). No differences were found in FCR and protein efficiency ratio among the treatments. Inclusion of both crab meals in diets significantly decreased the lipid content in whole fish compared with the control animals. On the other hand, no differences in muscle composition were found between the diets. Feeding both crab meals resulted in colour improvement compared with that of the control fish, with better hue values for the RC meal group than those for the MC meal group. The crab meals tested in the present study are suitable as a partial replacement for fish meal in diets for the red porgy, with the MC meal improving growth and both crabs meals improving skin colour, with further improvements in skin colour produced in fish‐fed diets containing the RC meal.     

Carotenoid deposition in pen-reared salmonids fed diets containing oil extracts of red crab (Pleuroncodes planipes)

The rate of deposition of carotenoids in pen-reared coho salmon was investigated by the addition of known carotenoid levels to diets. The carotenoids added to the diets were derived from red crab (P. planipes), and a process is described for the preparation of a soya oil carotenoid concentrate. Using a 3-stage counter-current extraction process, extracts containing 155 mg/100 g oil were prepared from red crab (P. planipes). Oregon moist pellets containing 3, 6, and 9 mg carotenoid/100 g were prepared using these extracts and were fed to coho salmon (Oncorhynchus kisutch) for 120 days. The amount of carotenoid deposited in the flesh of the fish was related to the carotenoid content of the diet and to the weight of the fish. Fish fed diets containing 6 and 9 mg carotenoid/100 g for the same length of time contained 60% more flesh carotenoids than those fed 3 mg/100 g. In general, after 120 days of feeding, only those fish feeding on diets containing 6.0 and 9.0 mg carotenoid/100 g and weighing over 215 g were assessed as having good-to-excellent coloration. Analysis of the flesh showed that there was no correlation between its carotenoid and fat contents.     

Effect of Astaxanthin from Xanthophyllomyces dendrorhous on the Pigmentation of Goldfish, Carassius auratus

Two experiments were conducted to evaluate the addition of astaxanthin from red yeast, Xanthophyllomyces dendrorhous, in the diets of goldfish, Carassius auratus. The first was designed to investigate the distribution of pigments in different tissues of goldfish and the effect of astaxanthin in the diet. The carotenoid concentration of tissues was not homogenous. The content of pigments in fish caudal fin was the highest followed by those of scales and head. Flesh had the least carotenoid deposition. Fish fed the diet containing 60 mg/kg astaxanthin had increased concentration of pigment in its head (22.6%), scales (45.5%), flesh (31.0%), and fin (21.2%), compared to fish fed basal diet (P < 0.05). Sixty parts per million astaxanthin had no effect on the weight gain and survival rate. High‐performance liquid chromatography analysis showed astaxanthin in its esterified form in goldfish. The second experiment was aimed at determining the dietary level of astaxanthin that improved color of goldfish. Goldfish were fed the same diet supplemented with 0, 10, 20, 40, 60, and 80 mg yeast astaxanthin/kg for 60 d. The deposition of carotenoids in goldfish fed diets supplemented with astaxanthin increased significantly (P < 0.05) after 15 d of feeding compared to that of the fish fed the diet without astaxanthin, but the effect of dosage of astaxanthin in the diets on the color of goldfish was not completely evident until Day 60 (P < 0.05). During the period of 15–45 d, the deposition of pigments in fish did not increase significantly (P > 0.05) in any treatment with the exception of the diet with 40 mg yeast astaxanthin/kg.     

Spirulina meal has acted as a strong feeding attractant for Litopenaeus vannamei at a very low dietary inclusion level

The present work aimed at studying the growth performance and feeding preference of Litopenaeus vannamei juveniles fed on diets supplemented or not with Spirulina meal. Litopenaeus vannamei juveniles (3.89 ± 0.25 g) were stocked for 72 days in 28 round 500‐L tanks at 44 shrimp/tank (77 juveniles/m²). The diets were supplemented with 0.5% of a commercial feed attractant (C25 and C50) or with Spirulina meal (S25 and S50). In C25/S25 and C50/S50 there were reductions of 25% and 50% in fishmeal inclusion level respectively. In a further study, two feeding trays with different diets were allowed to shrimp at the same moment and they were located in opposite walls of the tank. The feed remains in each feeding tray were collected and weighted to calculate the dry feed remains. The weekly growth rate of shrimp fed on S25 (0.89 ± 0.03 g) was not significantly different from those fed on C25 (0.89 ± 0.01 g). The attractiveness experiment showed that S25 was preferred significantly more by shrimp than C25. In conclusion, Spirulina meal added at 0.5% in a complete diet for L. vannamei juveniles, with 14% of Peruvian fishmeal, has proved itself as a nutritionally efficient feeding attractant.     

Effect of carotenoids and background colour on the skin pigmentation of Australian snapper Pagrus auratus (Bloch & Schneider, 1801)

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.     

Pigment deficiency correction in shrimp broodstock using Spirulina as a carotenoid source

In this study, an effort was made to cure the pigment deficiency syndrome (PDS) exhibited by pond‐reared Fenneropenaeus indicus (H.Milne Edwards) broodstock, using the blue‐green algae Spirulina as a carotenoid source in diet. The PDS symptoms included bleaching of ovary and reduced early larval performance. Biochemical analysis indicated reduced quantity of total carotenoids in egg and nauplii from the females with PDS. When PDS females were fed 30 g kg^?1Spirulina‐supplemented diet immediately after the appearance of symptoms, the egg and nauplii carotenoid values improved gradually and attained the pre‐PDS values after a minimum of 4 week period. Spirulina supplementation also improved significantly (P < 0.05) the spawn quality (hatch per spawn, nauplii per spawn, nauplii viability) and larval quality indices (P < 0.05). The egg and nauplii protein values exhibited a trend similar to carotenoids, confirming the influence of latter on protein stability previously reported by researchers. The study confirms the bioavailability of carotenoids from Spirulina to shrimp broodstock and recommends its regular inclusion in diet to preclude carotenoid deficiency‐related problems in shrimp hatcheries.     

Natural bixin as a potential carotenoid for enhancing pigmentation and colour in goldfish (Carassius auratus)

Discovering natural carotenoids for colour enhancement and health benefits of fish is important to develop new feed formulations. We have purified natural bixin from achiote seeds and evaluated the effect of colour enhancing and pigmentation in goldfish. Varying levels of bixin‐based diets were prepared with 420 g kg^?1 of crude protein and 120 g kg^?1 of lipid content. Our results clearly showed that bixin (0.05, 0.10, 0.20 and 0.60 g kg^?1) based diets significantly (P < 0.05) enhanced the skin and fin colour at 30 and 60 days compared to diet without bixin. Interestingly, diet which contains 0.20 g kg^?1 bixin and commercial feed (with astaxanthin) had similar effect on carotenoid deposition in skin. Moreover, total carotenoid deposition in fin was higher than in skin of all bixin‐containing diets. However, 0.60 g kg^?1 bixin‐containing diet had lower specific growth rate (1.01 ± 0.01) and higher feed conversion ratio (2.05 ± 0.19) compared to the control group. The present results demonstrate that achiote bixin can be successfully used as an alternative natural carotenoid source against synthetic astaxanthin in fish feed. Our data indicate that 0.20 g kg^?1 is a suitable dietary level of bixin to ensure strong pigmentation, acceptable growth and feed utilization in goldfish.     

Effect of dietary phosphorus supplementation on utilization of algae in the grow‐out diet of Nile tilapia Oreochromis niloticus

This research involved testing the replacement of corn gluten protein concentrate in the diet of 1.5 g Nile tilapia with biofuel algae‐based or algae supplemented with phosphorus diets. Experimental diets were formulated to replace 50% of the gluten meal protein in the control diet with biofuel algae protein (Alga50) or Spirulina (Spirulina50) protein. In addition, dicalcium phosphate (P) was added to the Alga50 at a concentration of 3.8% or 7.74% to mitigate aluminium (Al) toxicity and designated as Alga50 + P, and Alga50 + PP respectively. After 9 weeks of the feeding experiment, fish fed diets supplemented with P, Alga50 + P and Alga50 + PP differed significantly (P < 0.05) with respect to the feed conversion and protein deposition from the control. The mineral composition of the fish body showed a decrease in levels of Al and iron (Fe) due to the P supplements. The mineral composition of the faeces indicated that Al and Fe were excreted in the faeces and were not accumulated in the fish body. The effect of dicalcium P supplementation on the neutralization of Al in the diet resulted in improved fish growth and histological integrity of the gastrointestinal tract.     

Effects of the diet on seahorse (Hippocampus hippocampus) growth,body colour and biochemical composition

The short‐snouted seahorse (Hippocampus hippocampus) is a benthic fish that bases its survival on camouflage with the environment; therefore, both in wild and in captivity specimens, differences in coloration have been observed. This study was conducted to study the effect of five different diets, based on Artemia and frozen mysis, on fish survival, growth, skin colour parameters and biochemical composition. After 102 days of feeding different diets, no effect was observed on fish survival, growth, protein, ash or humidity content, except for colour changes on yellow and red fish. Differences on seahorse lipid and total carotenoids content were obtained in the experiment because of experimental diets. Fish eating Artemia showed the highest colour pattern response during the trial, with a maximum yellowness attained of 21. Additionally, a plateau of the skin colour expression for Artemia‐feeding fish was reached on day 180. A reversion of the yellowish skin colour was determined after a change of diet.     

Red Porgy,Pagrus pagrus,Larvae Performance and Nutritional Condition in Response to Different Weaning Regimes

Red porgy, Pagrus pagrus, is a candidate species for aquaculture diversification. The aim of this work was to assess whether an early supply of enriched Artemia (D1) or a direct step to dry diets (D3) would be advantageous weaning strategies for red porgy larvae, compared to a later supply of Artemia followed by dry diets (D2). Direct weaning to dry diet resulted in significantly lower growth, survival, pancreatic (trypsin and lipase), and intestinal (alkaline phosphatase) enzyme‐specific activity, with the exception of leucine‐alanine peptidase. The direct weaning strategy presented severe nutritional restrictions from early weaning stages with an associated delay of the maturation of digestive system. The two‐step strategy presented in D1 and D2 resulted in comparable results in most parameters, including survival. Weaning using enriched Artemia as an intermediate step is confirmed as the most adequate strategy for red porgy larvae. Digestive enzymes and selected fatty acids correlated well with performance responses to dietary regimes, thereby supporting the use of these parameters as sensitive and reliable indicators of red porgy nutritional or physiological status during larval stages.     

Effect of dietary canthaxanthin on the growth and lipid composition of red porgy (Pagrus pagrus)

A 24‐week feeding trial was conducted to study the possible effect of dietary canthaxanthin on red porgy growth and lipid composition. Two triplicate groups were established to test two experimental diets: (1) Control group fed a diet with no added carotenoids, and (2) canthaxanthin group (CTX100) fed a diet with 100 mg of synthetic canthaxanthin per kilogram of diet (CTX). Final and eviscerated weight were increased (P < 0.05) in the CTX100 treatment. The rest of growth performance parameters were not affected by the CTX diet. Whole‐fish total lipid content was decreased (P < 0.05) in CTX100 fish. In the liver, total lipids were not affected; however, saturated fatty acids in CTX100 treatment were significantly lower together with a higher n‐3 PUFA and a lower n‐6 PUFA, therefore increasing the n‐3/n‐6 ratio. Liver histology of CTX100 fish revealed decreased lipid vacuolization thus, significantly lowering hepatocyte area. In the muscle, total lipids were not affected. Similar to the liver, an increase of n‐3 PUFA and decrease n‐6 PUFA, led to a significant increase of the n‐3/n‐6 ratio. Concerning plasma, only total cholesterol (TC) was significantly affected by the CTX diet. Dietary canthaxanthin has an effect on red porgy lipid composition.