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Physical and chemical gradients across ecosystems, such as stream-to-lake continua within human-made reservoirs, provide valuable opportunities to examine how organisms respond to changing environments. We quantified the rate of dinoflagellate recruitment across a small reservoir to test the hypothesis that organisms are controlled by different factors along a reservoir continuum. We predicted that recruitment would be tightly coupled with reservoir physics in the riverine zone and closely related to water chemistry in the lacustrine zone. For the dominant dinoflagellate genus in the reservoir, Peridinium, recruitment from the sediments accounted for a median of 16% of increases in pelagic cell abundance throughout the summer. As predicted, Peridinium recruitment rates at the riverine site were correlated with physical variables, while at the lacustrine site, recruitment rates were highly correlated with water chemistry (e.g. nutrient ratios and dissolved oxygen). Recruitment patterns of the second most common genus, Gymnodinium, were not correlated with environmental variables, though Gymnodinium's much lower densities suggest that its dynamics were controlled by other factors. Our results reveal that the physical-biological coupling controlling algal recruitment, which can play a large role in pelagic population growth and bloom formation, can vary substantially on a spatial gradient within even a small reservoir. [ABSTRACT FROM AUTHOR]

Selenium (Se) is an essential nutrient required by Se-dependent proteins, termed selenoproteins. The selenoprotein family is small but diverse and includes key proteins in antioxidant, redox signaling, thyroid hormone metabolism, and protein folding pathways. Methylmercury (MeHg) is a toxic environmental contaminant that affects seafood safety. Selenium can reduce MeHg toxicity, but it is unclear how selenoproteins are affected in this interaction. In this study we explored how Se and MeHg interact to affect the mRNA expression of selenoprotein genes in whole zebrafish ( Danio rerio ) embryos. Embryos were obtained from adult zebrafish fed MeHg with or without elevated Se in a 2×2 factorial design. The embryo mRNA levels of 30 selenoprotein genes were then measured. These genes cover most of the selenoprotein families, including members of the glutathione peroxidase (GPX), thioredoxin reductase, iodothyronine deiodinase, and methionine sulfoxide reductase families, along with selenophosphate synthetase 2 and selenoproteins H, J-P, T, W, sep15, fep15, and fam213aa. GPX enzyme activity and larval locomotor activity were also measured. We found that around one-quarter of the selenoprotein genes were downregulated by elevated MeHg. These downregulated genes were dominated by selenoproteins from antioxidant pathways that are also susceptible to Se-deficiency-induced downregulation. MeHg also decreased GPX activity and induced larval hypoactivity. Elevated Se partially prevented MeHg-induced disruption of selenoprotein gene mRNA levels, GPX activity, and larval locomotor activity. Overall, the MeHg-induced downregulation and subsequent rescue by elevated Se levels of selenogenes regulated by Se status suggest that Se deficiency is a contributing factor to MeHg toxicity. [ABSTRACT FROM AUTHOR]

Highlights: [•] We examined the interactive effects of dietary SeMet and MeHg on female zebrafish. [•] Elevated SeMet reduced Hg concentrations in both adult fish and their eggs. [•] The positive effect of SeMet on egg Se concentrations was enhanced by MeHg. [•] Elevated SeMet reduced MeHg induced toxic effects on fish growth and survival. [•] Negative effects of elevated SeMet on fish reproduction were increased by MeHg. [ABSTRACT FROM AUTHOR]

The objective of this study was to examine the biochemical composition of intensively reared rotifers after enrichment with three commonly used enrichment media, Multigain, Ori-Green and DHA-enriched freshwater algae Chlorella, using standard enrichment protocols at a local cod larvae producer and compare it with that of natural zooplankton from Lofilab AS, a cod larvae producer using semi-intensive rearing techniques. Unenriched rotifers were analysed to examine whether the enrichment procedures were successful in increasing the content of essential nutrients to level requirements for marine fish larvae. Neither total lipids nor proteins were affected by enrichment. Unenriched rotifers were significantly lower in highly unsaturated fatty acids ( HUFAs) and significantly higher in linoleic acid ( LA, C18:2, n-6), than were zooplankton. Enrichment with Chlorella and Multigain increased the HUFAs significantly, while they were slightly reduced after enrichment with Ori-Green. Total amino acids and mineral content were unaffected by enrichment. Zooplankton was rich in taurine and selenium, whereas rotifers were devoid of it, both prior to and after enrichment. Using zooplankton as a reference for the nutritional requirements of marine fish larvae, results from this study demonstrate that enrichment media currently in use are not effective for enhancing the nutritional quality of rotifers. [ABSTRACT FROM AUTHOR]

Abstract: Rotifers are used as the first feeding diet for the larvae of many commercially produced marine fish species. However, the nutritional requirements of marine fish larvae appear to be better fulfilled by their wild feed, copepods. Consequently, rotifers are fed diets that alter their body composition to better imitate copepod composition and this results in greater success when rearing rotifer fed marine fish larvae. Despite this, copepod fed fish larvae still have higher growth rates and survival than rotifer fed larvae. This may occur because of the less investigated mineral differences that exist between rotifers and copepods. The concentration of selenium (Se) in rotifers Brachionus sp. (0.08–0.09mg Se kg−1 dry weight) can be over 30 fold lower than the concentration found in copepods (3–5mg Se kg−1 dry weight). In this study, the enrichment and retention of Se in rotifers fed Se enriched yeast (Se-yeast) were investigated. Rotifer Se concentration increased linearly with increasing levels of Se-yeast, with rotifers reaching a maximum of 138mg Se kg−1 dry weight. The use of Se-yeast was highly effective, with only 1% of the batch culture or short term enrichment diet needed to be replaced with Se-yeast to achieve copepod Se levels. At this feeding level there were no negative effects on rotifer egg ratio or population growth. Uptake of Se from Se-yeast was over 40 fold higher than obtained from using sodium selenite in short term enrichments (3h). Se-yeast enriched rotifers had a high retention (100–85%) of Se for up to 10h storage in clear water at cold (10°C) or warm (20°C) temperatures, while storage in green water (with algae) resulted in a slightly lower Se retention (65%) in a similar time period (8h). Overall, rotifers enrichment with Se-yeast resulted in reproducible concentrations of Se that were then retained for extended periods of time. This will allow Se-yeast enriched rotifers to be used as a Se delivery method for fish larvae nutritional requirement or toxicological studies. [Copyright &y& Elsevier]

Vitamin E is a generic term for a group of lipid-soluble molecules, the tocopherols and tocotrienols, which have a function in the protection of organisms against lipid oxidation and which also may have other, more specific biological functions. In fish, as in other vertebrates, α-tocopherol (TOH) is preferentially retained in the body compared to the other tocopherols, probably because of the presence of a tocopherol transfer protein (TTP) in the liver which binds the tocopherols with different affinities and returns them to the circulation. Tocopherols that bind weakly to TTP are to a greater extent excreted in the bile. α-TOH interacts with other nutrients, and the requirement therefore varies with the dietary composition. High levels of polyunsaturated fatty acids, and low levels of vitamin C, selenium and astaxanthin increase the requirement. This is attributed to the dynamic nature of both lipid oxidation and the antioxidant defence, where oxidized vitamin E is recycled by other antioxidants. The interactions also determine the display of vitamin E deficiency signs, immune responses and effects on flesh quality. Within the mammalian nutrition research community, there is a controversy as to whether vitamin E is primarily an antioxidant or a specific modulator of cell signalling through regulation of enzyme activities and gene expression and some of the hypotheses are presented in this review. [ABSTRACT FROM AUTHOR]

Butylated hydroxyanisole (BHA) is a phenolic antioxidant that is used as a food additive, particularly in fats and oils, and it is also authorized as a feed additive in the European Union for all animal species with a maximum concentration of 150 mg kg−1 feed (alone or in combination with ethoxyquin and/or butylated hydroxytoluene). Information on the BHA levels in food of animal origin is scarce, as is literature on the transfer of BHA from feed to animal products. Consequently, the current feeding trial was conducted under realistic rearing conditions to determine the retention of BHA in Atlantic salmon ( Salmo salar) fillets. Four different concentrations of BHA in feed were tested (0, 48.5, 92.5 and 225 mg BHA kg−1 feed), and fish were sampled after 4, 8 and 12 weeks dietary exposure, and after a 2-week starvation period, which is representative of commercial salmon farming in Norway. The levels of BHA in salmon fillets were fairly dose dependent during the feeding period. A steady state in fillet residues was reached after 4 weeks of administration of BHA. After the 2-week withdrawal period, BHA was not detectable (<7 μg kg−1) in either fish fillets or livers. [ABSTRACT FROM AUTHOR]

The current best practice intensive culture of larval Atlantic cod includes feeding rotifers from onset of exogenous feeding until 25–30 days after hatching. These larvae grow considerably slower and develop higher frequencies of deformities than larvae reared in semi-extensive systems, using copepods as feed. The present study compares the micronutrient concentrations in rotifers with those of copepods, with the aim of identifying nutrients that may be limiting for normal growth and development of cod larvae. An additional criterion used is the nutrient requirements given for fish in general, by NRC (1993) , as nutrient requirements of cod remains to be determined. Rotifers were fed on four different diets, consisting of baker's yeast with cod liver oil (3.3 : 1 dry weight (DW)/v), baker's yeast with Algamac 2000TM (3.5 : 1 DW), baker's yeast with live algae Chlorella (4.1 : 1 DW), and Culture Selco 3000TM (CS). CS was a complete commercial diet for rotifers while the other diets are considered as based on raw ingredients. Compared with copepod nutrient levels, rotifers grown on yeast-based diets supplemented with either cod liver oil, Algamac 2000 or Chlorella were apparently sufficient for covering the requirements in cod larvae for all the B-vitamins, except thiamine. Rotifers cultured on the CS diet also had sufficient amounts of thiamine. Of the minerals, only calcium and magnesium were sufficient, using this criterion while iron was on the borderline. However, with reference to the requirements given for larger fish ( NRC 1993 ), only thiamine, vitamin A, manganese, selenium and perhaps copper, appear too low in the rotifers cultured without extra micronutrient supplementation. The other nutrients were present at levels intermediate between copepod and fish requirement levels. This study suggests that it is necessary to develop enrichment techniques to produce rotifers with sufficient amounts of all micronutrients. Such techniques will also be important tools for determining which nutrients are present at levels below the actual requirements in cod larvae. [ABSTRACT FROM AUTHOR]

Abstract: Lipid spray beads (LSB) containing high concentrations of phospholipids were produced in order to improve their dispersion in both fresh and saltwater. The beads were developed to deliver both fat-soluble and water-soluble micronutrients to Artemia and other suspension feeders. LSB were prepared by spraying molted lipid into a chamber that was cooled with liquid nitrogen in order to solidify the lipid beads. Addition of soy lecithin to LSB did not affect retention of glycine when the beads were suspended in distilled water. There was an initial loss of 80% incorporated glycine after LSB were suspended in water for 20min. Artemia readily ingested riboflavin-containing LSB and their full guts were evident within 30min of feeding. The riboflavin content of Artemia could be increased from 55± 0.6 mg kg−1 (dw) to 329±62 mg kg−1 (dw) after 1h enrichment. LSB prepared with phospholipids are promising vehicles for enrichment of suspension-feeding organisms used as feed for larval marine fish and crustaceans as well as other suspension feeders. [Copyright &y& Elsevier]

Atlantic halibut juveniles, which have been fed Artemia during larval development, frequently demonstrate malpigmentation and impaired eye migration. This is in contrast to the high percentage of normally developed larvae fed copepods, reared under similar conditions. Nutrition is therefore an important component influencing larval development. Analyses of the nutrient composition of Artemia and copepods show that Atlantic halibut larvae fed Artemia probably receive sufficient amounts of vitamin A by converting canthaxanthin, while iodine may be deficient, possibly leading to interrupted thyroid hormone synthesis. An unbalanced fatty acid composition, such as high levels of arachidonic acid and low levels of docosahexaenoic acid, can be another limiting factor in Artemia. Vitamin A, fatty acids and thyroid hormones have all been shown to affect pigmentation in flatfish. They are ligands to nuclear receptors, thyroid hormone receptors, retinoic acid receptors, retinoic X receptors and peroxisomal proliferator-activated receptors, which are members of the superfamily of steroid hormone receptors. The receptors interact with each other to promote gene expression that modulates proliferation and differentiation of cells. Our hypothesis is that these interactions are important for development during flatfish metamorphosis. Very little data exist on the topic of impaired eye migration. However, energy limitation, iodine deficiency and an unbalanced fatty acid composition have been proposed as possible explanations. Here, we review the literature on development of pigment cells and the possible mechanisms behind the effects of vitamin A, fatty acids and thyroid hormone on pigmentation and eye migration during development of Atlantic halibut larvae. [ABSTRACT FROM AUTHOR]

Atlantic cod, initial weight 0.26 g, were fed diets varying in added protein from 530 to 830 g kg−1, lipid from 50 to 300 g kg−1 and carbohydrate from 0 to 150 g kg−1 of dry weight, according to a three-component mixture design. Analysed values of protein and lipid were 500–770 g kg−1 and 30–270 g kg−1, respectively. Analysed carbohydrate levels were as added. Increasing levels of both lipid and carbohydrate had a positive effect on fish growth ( P < 10−3), whereas protein levels above 600 g kg−1 gave a reduction in growth ( P < 10−4). The effects on growth were evident in fish less than 4 g, whereas fish growth between 4 and 6 g was unaffected by the dietary variation. It is hypothesized that the reduction in growth at high protein levels in fish of less than 4 g could be owing to incomplete utilization of protein, as the stomach of cod is not fully developed before the fish is approximately 1 g. Mortality and cannibalism were high in fish less than 4 g but low when the fish grew from 4 to 6 g. There was a significant decrease in cannibalism with increasing dietary lipid during the first half of the experiment ( P < 0.05) and cannibalism was consistently high in fish fed less than 150 g kg−1 lipid. The lipid level in whole fish increased with increasing dietary levels of lipid ( P < 10−6) and carbohydrate ( P < 10−4), whereas the liver lipid level increased with increasing dietary lipid up to 200 g kg−1 ( P < 10−6) and decreased thereafter ( P < 10−4). Whole body glycogen increased slightly with increasing levels of dietary carbohydrate ( P < 0.05) and was not affected by the other dietary variables. Liver glycogen increased in response to increasing dietary carbohydrate ( P < 10−5) and decreasing levels of dietary lipid ( P < 10−5). An abrupt increase in liver glycogen was seen with the reduction in dietary lipid from 100 to 50 g kg−1. The hepatosomatic index increased in response to both dietary lipid and carbohydrate ( P < 10−6). It is concluded that the protein requirement of young cod is less than 500 g kg−1 of dry diet. Fish of less than 4 g should not be given more than 620 g kg−1 protein and should be supplemented with 150–200 g kg−1 lipid. Carbohydrate up to 150 g kg−1 of dry diet promoted growth and did not seem to affect the fish negatively. Fish above 4 g can be given diets varying in protein and carbohydrate over the wide range of concentrations used in the present study, but lipid supplementation should be restricted to between 100 and 200 g kg−1. [ABSTRACT FROM AUTHOR]

An experiment with 2(7 − 3) reduced factorial design was conducted to study the biological effects of pro- and antioxidant micronutrients and lipid in Atlantic salmon. Vitamins C and E, astaxanthin, lipid, iron, copper and manganese were supplemented at high and low levels. For vitamins and minerals, high levels were chosen to be below the anticipated toxic level and the low levels were just above the requirement (vitamin C, 30 and 1000 mg kg−1; vitamin E, 70 and 430 mg kg−1; Fe, 70 and 1200 mg kg−1; Cu, 8 and 110 mg kg−1; Mn, 12 and 200 mg kg−1). For astaxanthin, the dietary levels were 10 and 50 mg kg−1 and for lipid, 150 and 330 g kg−1. The experiment was started with postsmolts (148 ± 17 g) and lasted for 5 months. The variation in micronutrients had only minor effects on growth, feed conversion and fillet quality, measured as lipid and astaxanthin deposition. High dietary lipid had a profound positive effect on growth and feed conversion but gave fillets nearly two times the fat content that was found in fish fed the low lipid diet. Astaxanthin deposition in the fillet was primarily affected by dietary astaxanthin with a positive effect of high dietary lipid in week 14 but not in week 23. Vitamin E protected the fillet against iron ascorbate stimulated oxidation, with no effect of the other nutrient variables. [ABSTRACT FROM AUTHOR]

Abstract The development of cataracts in Atlantic salmon, Salmo salar L., was studied in 16 groups of smolts fed diets differing in prooxidant (iron, copper, manganese) and antioxidant (vitamin E, vitamin C, astaxanthin) composition and lipid level for 23 weeks in sea water, using a 27--3 reduced factorial design. The seven dietary variables were systematically varied at low (requirement level and 150 g lipid kg-1 ) and high levels (below known toxic levels and 320 g lipid kg-1 ). A mean endpoint cataract incidence of approximately 36% was observed. High dietary levels of vitamin C and astaxanthin reduced cataract frequency, whereas high dietary lipid level, iron and manganese were associated with increased cataract frequencies. Considering the nutritional status of selected organs of the fish, only the status of ascorbic acid correlated negatively to cataract development (P < 0.05). The lens glutathione (GSH) status was not correlated to cataract frequency, nor statistically explained by the dietary variables. However, the study shows that balancing the diet with respect to pro- and antioxidant nutrients may significantly protect Atlantic salmon against development of cataracts. An incidence of reversible osmotic cataract observed at week 14 was positively correlated to plasma glucose concentration. [ABSTRACT FROM AUTHOR]

Atlantic halibut larvae were fed docosohexanoic acid- (DHA) selco enriched Artemia (RH-cysts) or wild zooplankton in duplicate tanks from first-feeding and 60 days onward. The zooplankton were collected from a fertilized sea water pond and consisted mainly of different stages of Eurytemora affinis and Centropages hamatus . There were no differences in survival, or in growth during the first 45 days of feeding, between larvae fed the two prey items, but the larvae fed Artemia showed much higher incidence of malpigmentation and impaired eye migration than larvae fed zooplankton. The prey organisms contained similar amounts of dry matter and protein, but Artemia was higher in lipid and glycogen than the zooplankton. Larvae fed Artemia were higher in both glycogen and lipid than the zooplankton-fed larvae towards the end of the feeding period. There were large differences between the prey organisms in the concentrations of essential fatty acids (% of total fatty acids) which was reflected in the fatty acid composition of the larval body. It is concluded that the macronutrient composition of Artemia in the present study was probably within the optimal range for promotion of growth and survival in young Atlantic halibut. The concentration of n-3 HUFA, and especially DHA, is however, very much lower in enriched Artemia than in copepods, and may be one of the factors triggering developmental errors in Atlantic halibut. [ABSTRACT FROM AUTHOR]

Abstract Small raceways were used in a weaning experiment with Atlantic halibut (Hippoglossus hippoglossus L.) larvae. The size of the tanks was 1.0 × 0.4 m with a 1- to 2-cm water level. Duplicate larval groups were transferred to the raceways from circular first feeding tanks at 0.07, 0.10 and 0.16 g wet weight, while recommended weaning size of this species is 0.2–0.3 g. During the first 7 days of weaning, Artemia was used as a food supplement in combination with the formulated dry feed. Thereafter only dry feed was used. The dry feed used in this experiment was produced by a special heat technique. The 0.07, 0.10 and 0.16 g larval groups were evaluated after 31, 25 and 17 days respectively (same date) The corresponding average survival was 81.4%, 78.0% and 96.6% and the specific daily growth rate was 3.18%, 3.17% and 2.38% respectively. In the Artemia control group, a survival rate of 96.0% and a growth rate of 5.28% was achieved. To evaluate the weaning success, the groups were followed in a 22-day post-weaning period on a commercial dry diet. Higher growth rates, 5.8–6.9%, were then obtained in all experimental groups, except control. The survival here averaged approximately 80% in the three experimental groups, but showed some differences between replicates. One hundred per cent survival was achieved during weaning in the former Artemia group. From the start of weaning to the end of the post-weaning period, the survival rates averaged 64% for the 0.07 and 0.10 g groups, approximately 80% for the 0.16 g group and 96% in the Artemia control group. Higher variance (CV) through the experiment and highest growth of the 75% quartiles of the fish groups compared with the 50% and 25%, indicated suppressed growth of the smaller fish. The successful weaning at these small sizes considerably reduced the live food period. Based on the present knowledge of the energetic demands of this species, it is calculated that weaning at 0.07 g compared with 0.25 g will reduce the amount of Artemia needed by at least 60%. No differences in pigmentation or degree of completed eye migration were detected between groups, indicating that this is determined at earlier developmental stages. [ABSTRACT FROM AUTHOR]

Abstract Atlantic salmon smolt (64 g) were fed 40, 300 or 1100 mg kg[sup -1] all-rac-α-tocopheryl acetate feed under normoxic and moderate hyperoxic conditions for 12 weeks. After 7 weeks, however, the hyperoxic fish were subjected to a temporary severe supersaturation of dissolved oxygen with development of gas bubble disease and substantial mortality as a result. Liver α-tocopherol (α-TOH) levels reflected the dietary input after 6 and 12 weeks of feeding. Increased levels of thiobarbituric-reactive substances (TBARS) in the liver of hyperoxygenated fish after 6 weeks indicate that moderate hyperoxic conditions may represent an oxidative challenge to the fish. After 12 weeks, liver ascorbic acid (AA) content was reduced in hyperoxygenated fish, and a decreasing tendency was also found in the liver content of α-TOH. Effects of oxygen supersaturation were also observed on liver antioxidant enzyme activities, content of glutathione and total mercapthans in liver, phagocytic chemiluminescent response and total plasma protein level, indicating a disturbed redox balance. No effects of dietary vitamin E were observed on any of the measured parameters, indicating that high levels of dietary vitamin E under these circumstances did not protect the fish against oxidative stress. [ABSTRACT FROM AUTHOR]

Abstract The influence of α-tocopheryl acetate (α-TOAc) on plasma concentration and fillet deposition of dietary astaxanthin was investigated in Atlantic salmon Salmo salar L. The diets were added 30 or 50 mg kg[sup –1] astaxanthin, and 200, 400 or 800 mg kg[sup –1] α-TOAc at each astaxanthin level. Improved flesh deposition of astaxanthin by 8–14% was achieved for fish fed diets with 30 and 50 mg kg[sup –1] astaxanthin, respectively, by the dietary addition of 800 compared with 200 mg kg[sup –1] α-TOAc. These results were supported by CIE[1976]L*a*b* tristimulus redness measurements (a* value). Plasma astaxanthin concentration mirrored the muscle astaxanthin concentration in the groups of fish fed a diet containing 30 mg kg[sup –1] astaxanthin. The salmon fed a high astaxanthin and low α-TOAc diet had the highest plasma concentration of idoxanthin (P < 0.05). Astaxanthin retention was significantly higher (P < 0.001) in salmon fed 30 mg kg[sup –1] astaxanthin than in those fed 50 mg kg[sup –1] astaxanthin, but was not significantly affected by dietary α-TOAc. Liver weight, body weight, specific growth rate, feed/gain ratio and mortalities were not affected by dietary α-TOAc levels. In conclusion, the dietary addition of α-TOAc appears to increase astaxanthin fillet deposition in salmonids and may reduce the demand for astaxanthin supplementation. The effect was rather small and requires verification. [ABSTRACT FROM AUTHOR]

The loss of fish in the seawater (SW) phase of Atlantic salmon farming is high, and a major proportion of this loss occurs in the period just after SW transfer. In the current study, we hypothesize that improvements made to the diet during the freshwater (FW) stage affect fish growth, survival and robustness later in the SW stage. To test this, salmon parr were fed five experimental diets in FW at 12 °C. In addition to a commercial-like control diet, fish were fed a diet with changed FA composition aimed to be more like the natural feed of salmon in FW, a diet with increased concentrations of selected AA/N-compounds (methionine, lysine, threonine and taurine), a diet with increased concentrations of methionine and certain B-vitamins (folate, B 12 and B 6) and a final diet combining all of these potential improvements. At the time of SW transfer, the robustness of fish fed the different diets was tested by direct transfer to SW at three different temperatures (8, 12 and 16 °C, without prior acclimation), as well as transfer into open net pens, while fed on a common commercial diet. Growth and proximate composition of the fish did not differ between the diet groups. All diet groups seemed to handle transfer to SW well, and while SW transfer elicited a stress response in the fish, this was not significantly different between diet groups. Fish transferred to SW at 8 °C had higher mortality, reduced mucus layer and increased prevalence of scale loss and wounds, but this applied to all diet groups. Hence, direct transfer to SW at a lower temperature than the fish has been acclimated to cannot be recommended. At the two highest temperatures, there were some differences between the groups in the severity of cataracts. Apart from this, none of the health- or welfare related parameters measured showed any difference between the diet groups, indicating that the control diet was already sufficient. • High loss of farmed salmon after seawater transfer was attempted ameliorated by diet. • The proposed dietary improvements did not affect survival or growth. • The fish did not handle direct transfer from 12 °C freshwater to 8 °C seawater well. • High rearing temperature and probably dietary histidine affected cataract. [ABSTRACT FROM AUTHOR]

Access to marine feed ingredients is considered a limiting factor for the rapidly growing aquaculture industry. With increasing inclusion of vegetable feed ingredients in aquafeeds, new challenges have arisen. Substituting marine oils and meals with vegetable ingredients has decreased the level of persistent organic pollutants ( POPs) in marine farmed fish such as Atlantic salmon. Consequently, this shift in feed ingredients has led to increased levels of polyaromatic hydrocarbons ( PAHs) in aquafeeds. Several of the PAHs listed are on EFSAs and EPAs list of priority substances. Not only are the carcinogenic and genotoxic properties of PAHs of concern, but also their ability to interact with and disrupt metabolic pathways such as vitamin metabolism and signalling. The interactions, and the potential depletion of vitamin stores that follows, are of particular interest as marine ingredients are naturally rich in micronutrients such as vitamins A and D. This study has summarized the current knowledge on the effect of PAHs commonly found in vegetable feed ingredients on vitamin metabolism/signalling and their possible implications in fish. [ABSTRACT FROM AUTHOR]

Introduction: Serological methods provide useful metrics to estimate age-specific period prevalence in settings of low malaria transmission; however, evidence on the use of seropositivity as an endpoint remains scarce in studies to evaluate combinations of malaria control measures, especially in children. This study aims to evaluate the immediate effects of a targeted mass drug administration campaign (tMDA) in Haiti by using serological markers.Methods: The tMDA was implemented in September-October 2018 using sulfadoxine-pyrimethamine and single low-dose primaquine. A natural quasi-experimental study was designed, using a pretest and posttest in a cohort of 754 randomly selected school children, among which 23% reported having received tMDA. Five antigens were selected as outcomes (MSP1-19, AMA-1, Etramp5 antigen 1, HSP40, and GLURP-R0). Posttest was conducted 2-6 weeks after the intervention.Results: At baseline, there was no statistical difference in seroprevalence between the groups of children that were or were not exposed during the posttest. A lower seroprevalence was observed for markers informative of recent exposure (Etramp5 antigen 1, HSP40, and GLURP-R0). Exposure to tMDA was significantly associated with a 50% reduction in the odds of seropositivity for Etramp5 antigen 1 and a 21% reduction in the odds of seropositivity for MSP119.Conclusion: Serological markers can be used to evaluate the effects of interventions against malaria on the risk of infection in settings of low transmission. Antibody responses against Etramp5 antigen 1 in Haitian children were reduced in the 2-6 weeks following a tMDA campaign, confirming its usefulness as a short-term marker in child populations. [ABSTRACT FROM AUTHOR]

Introduction: Serological methods provide useful metrics to estimate age-specific period prevalence in settings of low malaria transmission; however, evidence on the use of seropositivity as an endpoint remains scarce in studies to evaluate combinations of malaria control measures, especially in children. This study aims to evaluate the immediate effects of a targeted mass drug administration campaign (tMDA) in Haiti by using serological markers. Methods: The tMDA was implemented in September–October 2018 using sulfadoxine-pyrimethamine and single low-dose primaquine. A natural quasi-experimental study was designed, using a pretest and posttest in a cohort of 754 randomly selected school children, among which 23% reported having received tMDA. Five antigens were selected as outcomes (MSP1-19, AMA-1, Etramp5 antigen 1, HSP40, and GLURP-R0). Posttest was conducted 2–6 weeks after the intervention. Results: At baseline, there was no statistical difference in seroprevalence between the groups of children that were or were not exposed during the posttest. A lower seroprevalence was observed for markers informative of recent exposure (Etramp5 antigen 1, HSP40, and GLURP-R0). Exposure to tMDA was significantly associated with a 50% reduction in the odds of seropositivity for Etramp5 antigen 1 and a 21% reduction in the odds of seropositivity for MSP119. Conclusion: Serological markers can be used to evaluate the effects of interventions against malaria on the risk of infection in settings of low transmission. Antibody responses against Etramp5 antigen 1 in Haitian children were reduced in the 2–6 weeks following a tMDA campaign, confirming its usefulness as a short-term marker in child populations. [ABSTRACT FROM AUTHOR]

Introduction: Serological methods provide useful metrics to estimate age-specific period prevalence in settings of low malaria transmission; however, evidence on the use of seropositivity as an endpoint remains scarce in studies to evaluate combinations of malaria control measures, especially in children. This study aims to evaluate the immediate effects of a targeted mass drug administration campaign (tMDA) in Haiti by using serological markers. Methods: The tMDA was implemented in September–October 2018 using sulfadoxine-pyrimethamine and single low-dose primaquine. A natural quasi-experimental study was designed, using a pretest and posttest in a cohort of 754 randomly selected school children, among which 23% reported having received tMDA. Five antigens were selected as outcomes (MSP1-19, AMA-1, Etramp5 antigen 1, HSP40, and GLURP-R0). Posttest was conducted 2–6 weeks after the intervention. Results: At baseline, there was no statistical difference in seroprevalence between the groups of children that were or were not exposed during the posttest. A lower seroprevalence was observed for markers informative of recent exposure (Etramp5 antigen 1, HSP40, and GLURP-R0). Exposure to tMDA was significantly associated with a 50% reduction in the odds of seropositivity for Etramp5 antigen 1 and a 21% reduction in the odds of seropositivity for MSP119. Conclusion: Serological markers can be used to evaluate the effects of interventions against malaria on the risk of infection in settings of low transmission. Antibody responses against Etramp5 antigen 1 in Haitian children were reduced in the 2–6 weeks following a tMDA campaign, confirming its usefulness as a short-term marker in child populations. [ABSTRACT FROM AUTHOR]

Abstract: Rotifers are a common first feeding diet for rearing marine fish larvae. However, the levels of Mn, Cu, Zn, Se and iodine found in rotifers are low and may be insufficient to meet larval fish requirements. This study investigates increasing the concentration of Mn, Cu, Zn, Se and iodine simultaneously in rotifers (Brachionus plicatilis) in both short term enrichments (3h) or during batch cultures (6days), using either organically bound or inorganic mineral sources. This study demonstrates that rotifers can simultaneously be produced with Mn, Cu, Zn and Se concentrations up to and higher than the known requirements of fish, while increasing the level of iodine in rotifers was ineffective at the concentrations tested. To produce rotifers with copepod levels of Mn, Cu, Zn and Se, only 6% of a commercial rotifer enrichment diet had to be replaced with organically bound minerals, leaving a large percentage of the rotifer diet free to deliver other important nutrients such as lipid and proteins. Rotifers enriched to copepod mineral levels and stored for 18h retained 75–110% of their Se, Zn and Mn and 50% of their Cu. Overall, increasing rotifer mineral levels appears to be most effective when the mineral is available in an insoluble and hence ingestible form. [Copyright &y& Elsevier]

Four heat coagulated early weaning diets with increasing concentrations of pepsin hydrolysed protein, were investigated with regard to the change in protein quality during feed production and exposure to leaching. Water-soluble N, trichloroacetic acid-soluble N and amino acid (AA) profiles were determined in finished diets and in diets leached for 6 min. In vitro diet digestibility was measured and related to increasing inclusion of hydrolysed protein and N leakage. Seventeen to 47% of soluble N in the feed ingredients was made insoluble by heat denaturation during feed production, but the concentration of peptides and free amino acids (FAA) were not influenced. All peptides/FAA and 70–80% of water-soluble protein were lost after exposure to leaching. Increased inclusion of hydrolysed protein increased the loss of crude protein (15–30%). All taurine and 30% of histidine was lost during leaching, no other major changes in AA profile were found. There was no difference in digestibility between diets exposed to leaching. However, leached diets showed reduced digestibility as compared to diets that had not been exposed to leaching. In conclusion micro-bound type diets as used in this study have a low efficiency in delivering soluble N to fish larvae and should be carefully considered for this purpose. [ABSTRACT FROM AUTHOR]

Abstract: To investigate if digestion is limiting for absorption of dietary neutral lipids in Atlantic halibut (Hippoglossus hippoglossus, L.) larvae, absorption of triacylglycerol (TAG), diacylglycerol, (DAG), and monoacylglycerol, (MAG) as well as phosphatidylcholine (PC) was studied by tube-feeding larvae with radio-labelled lipids and tracing the radioactivity. PC was included to evaluate any difference in absorption of neutral versus polar lipids. The labelled lipids where deposited by tube-feeding before larvae were incubated individually for 18 h with collection of expired CO2. At sampling, the gut was separated from the body carcass and radioactivity traced in four different compartments, namely body carcass, gut, incubation water and CO2 expired from larvae. The relative (%) isotope distribution of each compartment was calculated and the dose size effect analysed by regression analysis. The results show that there is an increasing amount of evacuated unabsorbed neutral lipids as the complexity of the lipid increases (TAG>DAG>MAG). The larval faecal evacuation ranged from 66±20% of TAG to 9±6% of MAG. DAG was intermediate with 52±21% evacuated. Of the labelled PC, 37±16% was absorbed, but this can not be directly compared to the neutral lipids due to the different digestive enzymes that specifically hydrolyse neutral and polar lipids. Increasing the administered amount of lipids only slightly increased the total amount of labelled TAG and DAG that were actually absorbed, while there was a linear correlation between fed and absorbed MAG. The absorption of PC was also linearly related to the administered amount. The difference in net absorption of labelled TAG, DAG and MAG diets indicates that digestion is a limiting factor for absorption of neutral lipids in Atlantic halibut larvae. [Copyright &y& Elsevier]

This study sought to investigate whether a "natural diet" (mimicking the fatty acid composition of freshwater aquatic insects eaten by salmon parr) during the freshwater (FW) life stage of pre-smolt Atlantic salmon (Salmo salar L.) affected red blood cells and gill fatty acid composition as well as eicosanoid metabolism in gill during smolting at different temperatures. Before being transferred to seawater (SW), salmon parr were fed with a modified (MO) diet containing vegetable oils (rapeseed, palm, and linseed oils) supplemented with eicosapentaenoic acid (EPA) and arachidonic acid (ARA) to completely replace the fish oil (FO). Fatty acid composition in red blood cells and gill tissues was determined before SW transfer and six weeks after. Additionally, the expression of genes associated with eicosanoid metabolism and Na+/K+-ATPase (NKA) activity in salmon gill was examined at different temperatures before SW transfer and 24 h after. The results showed the changes in fatty acid composition, including sum monounsaturated fatty acids (MUFAs), docosahexaenoic acid (DHA), ARA, EPA, and sum n-6 polyunsaturated fatty acids (n-6 PUFA) in both red blood cells and gill tissues at the FW stage were consistent with the fatty acid profiles of the supplied MO and FO fish diets; however sum EPA and DHA composition exhibited opposite trends to those of the FO diet. The proportion of ARA, EPA, and n-6 PUFA increased, whereas sum MUFAs and DHA decreased in the red blood cells and gill tissues of MO-fed fish compared to those fed with the FO diet at FW stage. Additionally, 5-lipoxygenase-activating protein (Flap) expression was downregulated in MO-fed fish prior to SW transfer. During the process of SW transfer at different temperatures, the MO diet remarkably suppressed NKAα1a expression in MO-fed fish both at 12 and 16 °C. The MO diet also upregulated phospholipase A2 group IV (PLA2g4) expression in gills at 8, 12, and 16 °C, but suppressed phospholipase A2 group VI (PLA2g6) expression in gills at 12 °C compared to FO-fed fish at 12 °C and MO-fed fish at 8 °C. The MO diet also upregulated Cyclooxygenase 2 (Cox-2) expression at 8 °C compared to FO-fed fish and increased Arachidonate 5-lipoxygenase (5-Lox) expression in MO-fed fish at 16 °C compared to both FO-fed fish at 16 °C and MO-fed fish at 8 °C. Our study also determined that both SW transfer water temperatures and diets during the FW period jointly influenced the mRNA expression of PLA2g4 , PLA2g6 , and Lpl , whereas 5-Lox was more sensitive to dietary changes. In conclusion, the MO diet affected the fatty acid composition in gill and in red blood cells. When transferred to SW, dietary ARA supplementation could promote the bioavailability for eicosanoid synthesis in gill mainly via PLA2g4 activation, and potentially inhibit the stress and inflammatory response caused by different water temperatures through dietary EPA supplementation. • Salmon parr were fed with a MO diet only containing vegetable oils supplemented with EPA and ARA. • The MO diet affected fatty acid composition synergistically in gills and red blood cells at FW stage. • A lasting impact of MO diet during FW stage on fatty acid composition after SW transfer. • The MO diet promoted the eicosanoid biosynthesis in gill during SW transfer. • The MO diet inhibited the inflammatory response during smoltification at different temperatures. [ABSTRACT FROM AUTHOR]

Atlantic halibut ( Hippoglossus hippoglossus L.) larvae were fed enriched Artemia or zooplankton in duplicate tanks from 0 to 60 days after first-feeding. Both diets and the larvae were analysed for vitamin A (VA) in order to confirm earlier findings, in which Artemia fed larvae had lower levels of VA compared with larvae fed zooplankton. Furthermore, we wanted to investigate the composition of the retinoids in the larvae. The results showed that Artemia and zooplankton contains low levels of VA, probably too low to sustain the assumed requirement. Nevertheless, larvae fed Artemia had the same level of retinal and retinol as larvae fed zooplankton. We found a significant lower level of retinyl esters in larvae fed Artemia. The total VA level was lower in larvae fed Artemia only at the end of the feeding trial after the onset of metamorphosis. Our conclusion is that feeding Artemia to Atlantic halibut larvae is not likely to cause VA deficiency. [ABSTRACT FROM AUTHOR]

Sixteen groups of post smolt, Atlantic salmon (Salmo salar) (initial weight 148 ± 17 g) were fed diets with different lipid content and composition of pro- and antioxidants (vitamin E, vitamin C, astaxanthin, Fe, Cu and Mn). The composition of the experimental diets was based on a multivariate reduced factorial design (RFD) (27–3) with either high (+1) or low (–1) level (within limits of toxicity and requirement) of each of the seven dietary variables. Lipid class and fatty acid (FA) composition was analysed in retina, very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL). Further FA composition was analysed in fillet, liver and plasma. High dietary lipid increased growth, feed efficiency, fillet lipid level and the amount of LDL and HDL in plasma, whereas high dietary copper and high dietary vitamin E decreased the amount of plasma LDL. High dietary vitamin E decreased the amount of lipid and protein in LDL, whereas high dietary lipid increased cholesterol and cholesterol ester levels in plasma and HDL and the amount of lipid in LDL. Dietary astaxanthin and manganese affected retina PE levels. The FA composition did not differ significantly between the 16 diets. Dietary FA composition was reflected in fillet FA composition and gradually less in VLDL, LDL, HDL, plasma, liver and retina FA composition. Dietary lipid content influenced FA composition to some extent in the analysed tissues, i.e. generally high dietary lipid content led to a decreased relative amount of saturated and monoene fatty acids and an increase of the relative amount of polyene fatty acids. [ABSTRACT FROM AUTHOR]

The aim of the current study was to investigate how freshwater diets impact on immunity in Atlantic salmon smolts in freshwater, during transfer to seawater and in post smolts during the seawater stage with and without pancreas disease (PD) infection. Three specific freshwater diets were prepared: (i) A diet similar in composition to commercial salmon freshwater diets (Standard diet); (ii) A diet composed of vegetable oils (rapeseed, palm and linseed oils) mimicking the fat composition in aquatic insects – the natural diet of wild salmon in freshwater (Fatty acid diet); (iii) A diet enriched with possible immune modulating amino acids including dl -methionine, l -lysine, l -threonine and taurine (Amino acid diet). After seawater transfer, all fish were fed the same commercial diet. Head kidneys were extracted, and their leukocytes isolated from smolts right before transfer to seawater, from post smolts one and six weeks after transfer to seawater, and from post smolts in seawater after 8 weeks of ongoing PD infection. In addition, to provoke bacterial or virus induced inflammation in vitro, the individual leukocyte suspension from all fish were stimulated by lipopolysaccharide (LPS) or polyinosinic acid: polycytidylic acid (PIC). The transfer of smolts from fresh-to seawater changed the transcription of several types of genes. Particularly in isolates from fish fed the Standard or Fatty acid diet in freshwater, overall gene transcription (IL-1β , CD83 , INF-γ , cox2 , cd36 , MGAT2, catalase) declined. However, the Amino acid diet stimulated the LPS induced gene transcription of IL-1β , CD83 , Cox2 , and INF-γ at this stage. In freshwater smolts, PIC stimulated leukocytes showed higher transcription level of Mx and viperin in the Fatty acid and Amino acid diet groups compared to the Standard diet group. In seawater post smolts, Mx and viperin responded similarly to PIC challenge in all diet groups. Furthermore, leukocytes isolated from PD infected fish, continued responding to PIC, regardless of freshwater diet. • Modified Amino- and Fatty acid composition in freshwater diets can increase the immunological robustness of salmon parr towards virus infections during the freshwater phase. • The Amino acid composition in freshwater diets can be tailored to be protective against bacterial and oxidative damage in post smolts newly transferred to seawater. • When challenged with PIC, PD virus or PD virus + PIC, salmon immune cells use their energy to produce antiviral molecules, regardless of diet composition in freshwater. [ABSTRACT FROM AUTHOR]

The use of plant-based feeds warrants the supplementation with selenium (Se) to cover the requirement for Atlantic salmon. Depending on its chemical form, Se is a trace element with a narrow range between requirement and toxicity for most vertebrates. Information on safe upper limit for Atlantic salmon feed supplementation is lacking. Atlantic salmon (147 g) were fed a low natural background organic Se diet (0.45 mg Se kg −1 , wet weight (ww)) fortified with 5 graded levels of inorganic sodium selenite (0.45, 5.4, 11.0, 29.4, or 60.0 mg kg −1 ww) or organic selenomethionine (SeMet) (0.45, 6.2, 16.2, 21, or 39 mg kg −1 ww), in triplicate for 3 months. Excess Se supplementation was assessed by targeted biomarkers of Se toxicity pathways (e.g. markers of oxidative stress and lipid metabolism), as well as general adverse effect parameters (plasma biochemistry, hematology, liver histopathology, and growth). Safe limits were set by model-fitting the effect data in a dose-response (lower bound) bench mark dose (BMDL) evaluation. Fish fed the two highest selenite levels showed mortality while fish fed SeMet had no mortality. Fish fed 5.4–11 mg selenite kg −1 feed showed significantly (ANOVA, Tukey's t -test, p  < .05) increased liver oxidative stress, as seen from altered hepatic GSH and vitamin E levels, and liver damage as seen from increased plasma ALAT and liver histopathology such as degeneration and focal necrosis. Fish fed SeMet mainly showed liver pathology and kidney dysfunction as seen from altered plasma creatinine and total plasma proteins in fish fed ≥21 mg kg −1 , compared to control. For selenite exposed fish, a safe feed limit (BMDL) was set at 1–2 mg kg −1 ww feed (daily dose 0.01–0.02 mg kg BW −1  day −1 ), based on plasma ALAT increase, liver vitamin E depletion, and liver histopathology. For SeMet fed fish, the safe feed limit was higher than for selenite with a BMDL of 2.8 mg kg −1 ww (dose 0.03 mg kg BW −1  day −1 ), based on liver histopathology and plasma creatinine. In conclusion, with regards to fish health, Atlantic salmon seemed to tolerate the supplementation of selenite or SeMet to a level of total selenium of respectively 1–2 or 3 mg kg −1 feed, respectively, in a high plant-based salmon feed with background levels of 0.45 mg Se kg −1 . [ABSTRACT FROM AUTHOR]

Depending on its chemical form, selenium (Se) is a trace element with a narrow range between requirement and toxicity for most vertebrates. Traditional endpoints of Se toxicity include reduced growth, feed intake, and oxidative stress, while more recent finding describe disturbance in fatty acid synthesis as underlying toxic mechanism. To investigate overall metabolic mode of toxic action, with emphasis on lipid metabolism, a wide scope metabolomics pathway profiling was performed on Atlantic salmon ( Salmo salar ) (572 ± 7 g) that were fed organic and inorganic Se fortified diets. Atlantic salmon were fed a low natural background organic Se diet (0.35 mg Se kg −1 , wet weight (WW)) fortified with inorganic sodium selenite or organic selenomethionine-yeast (SeMet-yeast) at two levels (∼ 1–2 or 15 mg kg −1 , WW), in triplicate for 3 months. Apparent adverse effects were assessed by growth, feed intake, oxidative stress as production of thiobarbituric acid-reactive substances (TBARS) and levels of tocopherols, as well as an overall metabolomic pathway assessment. Fish fed 15 mg kg −1 selenite, but not 15 mg kg −1 SeMet-yeast, showed reduced feed intake, reduced growth, increased liver TBARS and reduced liver tocopherol. Main metabolic pathways significantly affected by 15 mg kg −1 selenite, and to a lesser extent 15 mg kg −1 SeMet-yeast, were lipid catabolism, endocannabinoids synthesis, and oxidant/glutathione metabolism. Disturbance in lipid metabolism was reflected by depressed levels of free fatty acids, monoacylglycerols and diacylglycerols as well as endocannabinoids. Specific for selenite was the significant reduction of metabolites in the S-Adenosylmethionine (SAM) pathway, indicating a use of methyl donors that could be allied with excess Se excretion. Dietary Se levels to respectively 1.1 and 2.1 mg kg −1 selenite and SeMet-yeast did not affect any of the above mentioned parameters. Apparent toxic mechanisms at higher Se levels (15 mg kg −1 ) included oxidative stress and altered lipid metabolism for both inorganic and organic Se, with higher toxicity for inorganic Se. [ABSTRACT FROM AUTHOR]

The extensive use of plant ingredients in novel aquafeeds have introduced mycotoxins to the farming of seafood. The emerging enniatin B (ENNB) and beauvericin (BEA) mycotoxins have been found in the novel aquafeeds and farmed fish. Little is known about the potential toxicity of ENNs and BEA in farmed fish and their feed-to-organ transfer. Atlantic salmon (Salmo salar) pre-smolt (75.3 ± 8.10 g) were fed four graded levels of spiked chemical pure ENNB or BEA feeds for three months, in triplicate tanks. Organismal adverse health end-point assessment included intestinal function (protein digestibility), disturbed hematology (red blood cell formation), bone formation (spinal deformity), overall energy use (feed utilization), and lipid oxidative status (vitamin E). Both dietary BEA and ENNB had a low (<∼0.01%) transfer to organs (kidney > liver > brain > muscle), with a higher transfer for ENNB compared to BEA. BEA caused a growth reduction combined with a decreased protein digestion and feed conversion rate- ENNB caused a stunted growth, unrelated to feed utilization capacity. In addition, ENNB caused anemia while BEA gave an oxidative stress response. Lower bench-mark dose regression assessment showed that high background levels of ENNB in commercial salmon feed could pose a risk for animal health, but not in the case of BEA. • Substitution of fish with plant ingredients increases mycotoxins in aquafeeds. • Dietary BEA causes growth reduction and feed conversion rate in salmon. • Dietary ENNB caused a stunted growth, unrelated to feed utilization capacity, and anemia in salmon. • Background levels of ENNB in salmon feed could form a risk to animal health. [ABSTRACT FROM AUTHOR]

In studies of marine larvae, it is common to use days post-hatch as a developmental reference point. We show that age is a poor measure of morphological and physiological development in Atlantic cod. Therefore, we propose a set of five developmental stages of Atlantic cod from start-feeding until the juvenile stage, based on cranial ossification as previously done in Atlantic halibut. Cod follows a sequence of cranial ossification that is to a large extent preserved in most fish species examined. These stages are therefore tools to standardize sampling and to reduce growth dependent variation in the analysis of larvae during development. We show that several developmental stages are present in the same rearing unit at a given time. We also demonstrate that nutrition during early development is a vital foundation for robust skeletal development. Cod larvae supplied with copepods instead of rotifers followed by Artemia , develop less skeletal deformities at 10 cm standard length, despite given the same formulated feed from 1.8 cm standard length and onwards. Statement of relevance This paper provides developmental stages that are vital for best practice protocols in aquaculture. By relating farming practices to developmental stages and not age, the right treatment ect may be provided. This manuscript does also highlight the importance of nutrition during live feed stages on events that may occur late in the production cycle. [ABSTRACT FROM AUTHOR]

Dietary selenium (Se) influences the glutathione peroxidase (GPx) activity and the thyroid hormone system in vertebrates, but these relations are poorly described in fish. The present study aimed to evaluate the effect of Se supplementation on Senegalese sole larvae, focusing on GPx activity and thyroid status. Two groups of larvae were fed on either control (C) or Se-enriched live feed, from 2 days after hatch (DAH) until 34 DAH. Senegalese sole larvae fed Se-enriched live feed significantly increased their whole-body Se, compared to larvae from C group. The activity of GPx was higher in larvae from Se group, suggesting that the levels of this mineral were suboptimal in the control diet. TH levels were also higher in larvae fed Se-enriched live feed, suggesting that Se may have a positive influence on the TH production in early life stages of marine fish larvae. [ABSTRACT FROM AUTHOR]

The present study assessed differences in fecundity and egg quality from Atlantic cod Gadus morhua fed isoproteic diets containing 13% fat (low fat, LF) or 20% fat (high fat, HF) and either stressed or left unstressed as a control over the spawning season. Each diet was fed to triplicate groups of G. morhua from June 2009, through to first maturation and spawning. In January 2010 sub-groups of G. morhua were moved to land-based spawning tanks where the experimental trial was carried out. At the start of the experiment, G. morhua fed the high-fat diet were significantly larger than G. morhua fed low-fat diet. These differences were maintained through the spawning season, although with a loss of mass in both dietary groups. Relative fecundity through the season was significantly lower in stressed G. morhua fed LF compared to unstressed G. morhua fed the same diet. Stressed G. morhua had a higher variability in weekly amount of eggs spawned, spawning occurred more irregularly, and the spawning period lasted longer than in unstressed G. morhua. Several egg quality variables were also affected: eggs from G. morhua fed LF and exposed to stress had lower fertilization and hatching rates compared to the unstressed G. morhua fed the same diet as well as all G. morhua fed HF. Gadus morhua fed a low-fat diet appeared less tolerant to stress than fish fed a high-fat diet. [ABSTRACT FROM AUTHOR]

Abstract: Dietary iodine may play an important role in the nutritional health of freshwater fish larvae. Artemia, commonly used for the culture of larval zebrafish (Danio rerio), contain low concentrations of iodine when compared with wild-caught zooplankton. Iodine concentrations of Artemia can be increased using wax spray beads (WSB) containing potassium iodide (KI; KI WSB); however, the availability of iodine in enriched Artemia for fish larvae is currently unknown. The objectives of this study were to: 1) evaluate the use of KI WSB for enrichment of Artemia with iodine; 2) determine if zebrafish larvae were able to obtain iodine from KI WSB-enriched Artemia; 3) investigate the effects of KI WSB-enriched Artemia on the growth, survival and thyroid status of larval zebrafish; 4) determine if Artemia were a potential source of exogenous thyroid hormones (TH) for larval fish; and 5) determine if KI WSB had an effect on bacterial concentrations associated with Artemia. A 24-day feeding trial was conducted to compare the effects of iodine-enriched Artemia with unenriched Artemia on the survival and growth of larval zebrafish. Zebrafish fed Artemia enriched with KI WSB showed a ten-fold increase in total iodine levels and increased survival when compared with larvae fed unenriched Artemia. Thirty-eight days-post-fertilization (dpf) zebrafish larvae fed iodine-enriched Artemia had lower epithelium to colloid (v:v) ratios when compared to those fed unenriched Artemia. Artemia were found to contain significant levels of outer-ring deiodinase and THs. KI WSB had no effect on the levels of marine bacteria associated with Artemia. The results of this study indicate that iodine contained in KI WSB enriched Artemia is available to larval fish. There was also evidence to suggest that early-stage zebrafish benefit from increased levels of dietary iodine. In addition, Artemia may provide larval fish with significant levels of exogenous THs and deiodinase. [Copyright &y& Elsevier]

To study the effect of dietary supplementation of iodine in Solea senegalensis, larvae were randomly distributed in six tanks. Larvae in three tanks were given rotifers and Artemia enriched with iodine in addition to Rich Advance or Super Selco from 2 days after hatch (DAH) until 31 DAH. Larvae in a second set of three tanks were fed control rotifers and Artemia, enriched only with Rich Advance or Super Selco. Samples were collected at 2, 5, 10, 15 and 31 DAH to determine dry weight, total length, myotome height and thyroid status. Larvae fed the iodine-enriched diet had significantly higher weight at 31 DAH and higher levels of whole body iodine concentration, compared to control larvae. At 31 DAH, larvae from the control treatment showed typical goitrous thyroid follicles. Thyroid cells of larvae from this treatment appeared columnar or afollicular, with the colloid partly or completely depleted, representative of hyperplasia (goitre). The lower growth rate in fish larvae from the control treatment was possibly a consequence of the hyperplasia, and the iodine enrichment prevented Senegalese sole larvae from developing goitre. This study demonstrates the importance of iodine enrichment of live feed for fish reared in a recirculation system. [ABSTRACT FROM AUTHOR]

Several synthetic antioxidants are authorized for use as feed additives in the European Union. Ethoxyquin (EQ) and butylated hydroxytoluene (BHT) are generally added to fish meal and fish oil, respectively, to limit lipid oxidation. The study was conducted to examine the concentrations of EQ, BHT and butylated hydroxyanisole (BHA) in several commercially important species of farmed fish, namely Atlantic salmon, halibut and cod and rainbow trout, as well as concentrations in fish feed. The highest levels of BHT, EQ and BHA were found in farmed Atlantic salmon fillets, and were 7.60, 0.17 and 0.07 mg kg−1, respectively. The lowest concentrations of the synthetic antioxidants found were in cod. The concentration of the oxidation product ethoxyquin dimer (EQDM) was more than ten-fold higher than the concentration of parent EQ in Atlantic salmon halibut and rainbow trout, whereas this dimer was not detected in cod fillets. The theoretical consumer exposure to the synthetic antioxidants EQ, BHA and BHT from the consumption of farmed fish was calculated. The contribution of EQ from a single portion (300 g) of skinned fillets of the different species of farmed fish would contribute at most 15% of the acceptable daily intake (ADI) for a 60 kg adult. The consumption of farmed fish would not contribute measurably to the intake of BHA; however, a 300 g portion of farmed Atlantic salmon would contribute up to 75% of the ADI for BHT. [ABSTRACT FROM AUTHOR]

Abstract: Commercially produced Atlantic cod (Gadus morhua L.) larvae are fed rotifers, while in the wild cod larvae feed on copepods. Rotifers contain up to 30-fold less selenium (Se) than copepods, and may contain insufficient Se to meet cod larvae requirements. In this study, rotifers were fed Se-enriched yeast (Se+rotifers) to obtain copepod levels of Se (3mgkg−1 dry weight (DW)), and the effects of feeding the Se+rotifers to cod larvae was investigated and compared to cod larvae fed control rotifers containing 0.7mgSekg−1 DW. No differences were observed in growth or survival between groups at the end of the rotifer-feeding period (29days post hatch (dph)), or in the rate of skeletal deformities at 120dph. Cod larvae fed Se+rotifers had increased whole-body levels of Se, and expression and activity of Se-dependent glutathione peroxidases during the rotifer-feeding period (3 to 29dph) compared to controls. Meanwhile no effect of the treatment was seen in the activity or mRNA expression of the deiodinases. There was no difference in thyroid hormone levels at 29dph, but the T3/T4 ratio was increased in the Se+larvae. Thyroid follicles of Se+larvae had increased total volume, colloid volume and ratios of epithelium to colloid compared to controls. The results demonstrate that Se-dependent enzyme mRNA expression and activities in cod are retained according to a selenoprotein hierarchy as found in other vertebrates, and suggest that rotifers need extra supplementation of Se to meet cod larvae requirements. [Copyright &y& Elsevier]

Genetic reference populations, particularly the BXD recombinant inbred (BXD RI) strains derived from C57BL/6J and DBA/2J mice, are a valuable resource for the discovery of the bio-molecular substrates and genetic drivers responsible for trait variation and covariation. This approach can be profitably applied in the analysis of susceptibility and mechanisms of drug and alcohol use disorders for which many predisposing behaviors may predict the occurrence and manifestation of increased preference for these substances. Many of these traits are modeled by common mouse behavioral assays, facilitating the detection of patterns and sources of genetic coregulation of predisposing phenotypes and substance consumption. Members of the Tennessee Mouse Genome Consortium (TMGC) have obtained phenotype data from over 250 measures related to multiple behavioral assays across several batteries: response to, and withdrawal from cocaine, 3,4-methylenedioxymethamphetamine; “ecstasy” (MDMA), morphine and alcohol; novelty seeking; behavioral despair and related neurological phenomena; pain sensitivity; stress sensitivity; anxiety; hyperactivity and sleep/wake cycles. All traits have been measured in both sexes in approximately 70 strains of the recently expanded panel of BXD RI strains. Sex differences and heritability estimates were obtained for each trait, and a comparison of early ( N = 32) and recent ( N = 37) BXD RI lines was performed. Primary data are publicly available for heritability, sex difference and genetic analyses using the MouseTrack database, and are also available in for quantitative trait locus (QTL) detection and genetic analysis of gene expression. Together with the results of related studies, these data form a public resource for integrative systems genetic analysis of neurobehavioral traits. [ABSTRACT FROM AUTHOR]

The study aims to test whether predigested dietary protein enhances the utilization of formulated diets at weaning, and also whether it stimulates intestinal maturation. In this study, Atlantic cod [ Gadus morhua L.; 41 days posthatch (dph)] and Atlantic halibut [ Hippoglossus hippoglossus L.; 63 days postfirst feeding (dpff)] were weaned onto diets with graded levels of protein hydrolysate. By increasing the inclusion of dietary protein as hydrolysate from 0 to 400 g kg−1, cod increased the rate of survival from 7 ± 1% to 18 ± 2% (82 dph; regression, P = 4*10−7). In halibut, the survival rate decreased from 57 ± 9% to 22 ± 7% as the inclusion of protein in the form of hydrolysate increased from 0 to 450 g kg−1 (119 dpff; regression, P = 8*10−5). Growth was not affected in any of the species. Results in specific activities of the intestinal enzymes leucine aminopeptidase (LAP) and alkaline phospatase (AP) supported the results in survival in halibut and partly also in cod, by showing increased activities in groups with increased survival (anova, P < 0.05). The lower optimal level of hydrolysed protein in halibut than in cod is suggested mainly because of a slower feeding practice in halibut, which allows more extensive nutrient leaching before ingestion. [ABSTRACT FROM AUTHOR]

Abstract: Culture of the early larval stages of many marine fish species is often characterized by high larval mortality and poor growth. Comparison of the nutritional composition of cultured live prey, such as species of rotifers and Artemia, with that of “natural” prey species, such as copepods, indicates possible deficiencies in essential micronutrients that could explain the poor performance of larvae fed on these cultured foods. Enrichment of live prey species by feeding them on artificial diets is difficult due to high leakage losses from microparticles in aqueous suspension. In this study, wax spray beads (WSB) consisting of bees wax, with or without a 5% w/w extract of a synthetic marine phospholipid (mPHL), were evaluated for their potential for delivery of water-soluble micronutrients and the antibiotic oxytetracycline (OTC) to Artemia. The micronutrient mix consisted of amino acids, vitamins and trace minerals and was based on the nutritional composition of copepods. Leaching experiments indicated that nitrogen (N) retention of WSB containing the micronutrient mix rapidly declined in the first 5 to 10 min of suspension in seawater; however, subsequent N losses over a 2 h period occurred at much lower rates, resulting in overall N retention efficiencies of 44% and 24% for WSB prepared with either 100% wax or 95% wax/5% mPHL, respectively. Substantial losses of labile micronutrients, such as vitamin A, vitamin E, astaxanthin, selenium, vitamin C and thiamin, occurred during WSB preparation. Furthermore, production of peroxidation products and losses of astaxanthin were greater with beads containing 5% mPHL compared with beads prepared with 100% bees wax. Artemia ingested and broke down riboflavin-containing WSB prepared with 100% bees wax and liberated riboflavin was observed in their digestive systems. Artemia fed OTC-containing WSB prepared with 100% bees wax retained OTC after purging their guts of ingested WSB. WSB may be useful in delivering water-soluble substances to Artemia as well as other marine suspension feeders capable of breaking down these beads by mechanical or enzymatic processes. The advantage of using wax as the lipid carrier, compared with phospholipid and triacylglycerol lipid types, is that it is relatively inert and will less likely react with incorporated materials to produce peroxides or result in excessive contributions to the lipid nutrition of the target organism. [Copyright &y& Elsevier]

Atlantic halibut ( Hippoglossus hippoglossus) achieve a mature gastrointestinal tract approximately 2 months after first feeding (12 °C). The immature digestion may be the reason that compound diets fail to sustain growth and survival in first feeding halibut larvae and in larvae of other marine fish species. On the other hand, larvae fed with live feeds are capable of extraction of sufficient quantities of nutrients to sustain high growth rates. A lower availability of the protein in formulated diets compared with live prey is considered to be an important reason for the low performance of formulated diets. One approach to increase dietary protein availability is supplementation of pre-digested proteins. Experiments using tube fed individual larvae show that halibut larvae are able to utilize hydrolysed protein more efficiently than intact protein. However, Atlantic halibut in culture did not respond well to dietary supplementation of hydrolysed protein, in contrast to some other species. One reason may be extensive leaching of pre-hydrolysed proteins from the microparticulate feed. Atlantic halibut are slow feeders and may thus suffer more from nutrient leaching than species eating more rapidly. Feed formulation techniques affect dietary protein leaching, and in this paper, different techniques and their impact on feed properties are described. Microbound diets are most widely used in larval rearing, but show high rates of nutrient leaching. Lipid-based capsules seem to have the best potential to prevent leaching, however, they are not able to deliver a complete diet. The high need for improvements in larval feed formulation techniques are clearly stated, and some suggestions are given. Among these are production of complex particles, where small lipid-based capsules or liposomes containing the low molecular weight water-soluble nutrients are embedded. In such feed particles the water-soluble molecules are protected from leaching. Techniques for delivery of water-soluble nutrients that are needed in large quantities, i.e. free amino acids or hydrolysed and water-soluble protein, remain to be developed. [ABSTRACT FROM AUTHOR]

Abstract: To determine the status of development of the intestine, the activities of intestinal leucine–alanine peptidase (Leu–ala), brush border membrane (bbm)-bound alkaline phosphatase (AP) and bbm-bound leucine aminopeptidase N (LAP) were analysed from first feeding to passed weaning in Atlantic halibut (Hippoglossus hippoglossus; 1–78 days post first feeding; dpff) and Atlantic cod (Gadus morhua; 0–72 dpff). Before conducting the ontogenetic studies, the enzyme assays used were optimised in relation to temperature and pH (only AP and LAP), and the Michaelis constant (K M; All enzymes) determined, in order to ensure valid data and to maximise the activity potentials. Leu–ala was used as a marker of intracellular digestion which was expected to decrease during the experimental periods. AP and LAP were used as markers of development of the bbm and achievement of an adult mode of digestion. In halibut, Leu–ala increased 11-folds (P =0.0002) in specific activity (mU (mg protein)−1) from first feeding to 34 dpff and thereafter a small decrease (0.65-fold; P =0.006) in activity was observed. In cod, the specific activity of Leu–ala varied randomly during the experiment. Distinct increases in specific activities of AP and LAP were observed from 29 to 52 dpff in halibut (fivefold; P <0.002) and from 29 to 37 dpff in cod (two–threefold; P <0.02). The bbm-bound activities of AP and LAP in percent of total intestinal activity of the respective enzyme increased from approximately 2 to 15% between 34 and 43 dpff in halibut (P <0.0003), confirming the results of specific activities. In cod, a similar result with AP was found between 29 and 51 dpff (P =0.0003). The increase in percentage of bbm-bound activity of LAP was later, increasing exponentially from constituting 5 to 31% of total individual activity between 37 and 72 dpff (P =0.0003). The experiments indicated that the digestion in halibut had advanced towards the adult mode at 40 to 50 dpff, while time of reaching the same maturational level in cod was less certain due to the different activity profiles of AP and LAP. As AP is well recognised as a bbm differentiation marker, it can be assumed that the intestine in cod matured when AP activity had reached an elevated level at approximately 40 to 50 dpff, whereas LAP possibly was induced later. Ceasing of the larval mode of digestion, expected to be indicated by reduced activity of Leu–ala, was not detected. [Copyright &y& Elsevier]

Abstract: In vitro methods have previously been utilised for the rapid and reliable evaluation of protein digestibility in fish. In this study we used in vitro methods to compare the digestibility of various live and artificial larval feeds and feed ingredients. Given previous suggestions that water-soluble dietary proteins are efficiently digested and utilised by stomachless fish larvae, we also analysed the content of water-soluble nitrogen in the feeds and feed ingredients and then measured the specific in vitro digestibility (simulated midgut conditions) of the water-soluble and insoluble fractions. The soluble nitrogen fractions were generally more digestible than the insoluble nitrogen fractions (P <0.05). A soluble reference protein (Na+-caseinate) was digested faster than the similar but insoluble reference protein (casein) although their final digestibility was the same (94%). Frozen live feeds (Artemia fransiscana and Calanus finmarchicus) contained high fractions of soluble nitrogen (54–67%) and also had high digestibility in vitro (84 and 87%, respectively). The in vitro digestibility of two formulated larval feeds tested was lower (53 and 70%) than the frozen live feeds. The digestibility of the ingredients of the protein-encapsulated feeds particles was reduced as a result of the production process (from 71 to 53%, respectively). Three meals of marine origin (fish meal, squid meal and fish roe meal) all had low contents of water-soluble nitrogen (11–17%) but showed different degrees of digestibility (77, 77 and 49%, respectively). The results also demonstrated that while pre-hydrolysis of a feed ingredient (fresh frozen cod fillet) almost doubled the water-soluble nitrogen fraction (from 34 to 65%) the positive effect of pre-hydrolysis on in vitro digestibility was much lower (from 80 to 86%). This demonstrates the complexity of assessment of bioavailability of dietary protein sources in larval fish; a number of factors such as leaching rates from feed particles, digestibility, digestion rates and absorption rates all need to be taken into account. [Copyright &y& Elsevier]

Flatfish metamorphosis is initiated by the actions of thyroid hormones (TH) and iodine is an essential part of these hormones. Hence, an iodine deficiency may lead to insufficient levels of TH and incomplete metamorphosis. In this study, different iodine sources for enrichment of Artemia were evaluated and the levels of iodine obtained in Artemia were within the range of 60–350 μg g−1 found in copepods. Larval Atlantic halibut was fed Artemia enriched with either normal DC-DHA Selco or DC-DHA Selco (commercial enrichments) supplemented with iodine from days 9 to 60 postfirst feeding. There was no significant difference in growth, mortality or metamorphic development between the groups. The analyses showed that we were able to enrich Artemia with iodine. Further, the larvae-fed iodine-enriched Artemia had higher whole body iodine concentration compared to larvae-fed Artemia without iodine enrichment. [ABSTRACT FROM AUTHOR]

Abstract: Leakage of water soluble nutrients from larval microparticulated feeds is probably extensive and needs to be further investigated. Leaching rates of 14C-labelled serine, pepsin hydrolysed, protein enriched 14C-algae extract and intact protein enriched 14C-algae extract were measured from three microparticulated feeds for marine fish larvae (heat coagulated, protein bond feed; agglomerated feed; protein encapsulated feed). The effects of particle size (<0.3 mm, 0.3–0.6 mm; 0.6–1.0 mm) and immersion time (1–60 min) in salt water were also tested. Leaching increased by decreasing molecular weight of leaching component (P <10− 5), by the feeds in order encapsulated, heat coagulated and agglomerated feeds (P <10− 5), by longer immersion time (P <10− 5), and by decreasing feed particle size (P <10− 5). Due to low protein content of the algae extract, the leaching rates of intact and hydrolysed algae extract did not represent absolute estimates for protein and hydrolysed protein leaching. A new estimate for leakage of hydrolysed protein was calculated based on molecular weight distribution of the hydrolysed algae extract analysed by cutoff centrifugation of the extract. Assuming that molecules<300–600 or <9–18 kD would leak, leakage of hydrolysed protein from the smallest feed particles after 5 min immersion would be 80–98%, 43–54% and 4–6% of the agglomerated, heat coagulated and protein encapsulated feeds, respectively. The feeds were also tested for preference in cod larvae of two different sizes (5.6±2.5 mg and 15.8±7.2 mg). The preference was highest for the heat coagulated feed in the first experiment (feed intake 0.32±0.06 mg dry feed larvae− 1) and the agglomerated in the second (2.04±0.32 mg dry feed larvae− 1), while the protein encapsulated feed was preferred at lower rates in both experiments (0.11–0.14 mg dry feed larvae− 1). [Copyright &y& Elsevier]

To determine developmental stages independent of eye migration, a highly plastic feature in Atlantic halibut, 180 sibling halibut larvae reared at an average temperature of 11.9 °C from first feeding and for a further 46 days were examined, cleared and stained for ossification and the cranial development was recorded. Morphological development and cranial ossification generally coincided. The order of ossification of cranial structures was: jaw structures, hyoid arch, opercular bones and structures of the neurocranium. The Frontale exhibited torsion correlated with eye migration, but calcification began earlier and full calcification was independent of ocular displacement. The appearance of ossified elements was used to group larvae into Stages 5–9, comprising premetamorphosis to climax metamorphosis, with significant morphometric differences between stages. The trajectory of juvenile development appears fixed by Stage 8. There was a linear relationship between stage and myotome height (R2=0.86) and stage and standard length (R2=0.80). The stage definitions were validated on two groups (n=23, n=101) of commercially produced larvae. Because metamorphosis is protracted in halibut, use of these stages and especially myotome height should help standardize sampling and analysis between experiments and between producers. [Copyright &y& Elsevier]

Larval nutrition affects post-metamorphic phenotype in Atlantic halibut and many deformities are related to skeletal development. In a multidisciplinary study, 24,000 sibling halibut larvae were reared at an average temperature of 11.9 °C on either enriched Artemia or natural zooplankton in duplicate treatments and the development followed. One hundred and eighty sibling larvae up to about climax metamorphosis at 46 days post start feeding (psf) were cleared and stained for bone, and stereological measurements of bone and body area and degree of eye migration were registered. From day 21 psf, the zooplankton-fed fish had more calcified matrix relative to body size than did Artemia-fed halibut and from day 35 psf, this difference was significant (33.7%±1.9 SD vs. 28.6%±4.1, P<0.05). When related to ontogeny, the zooplankton-fed fish had a higher average percentage ossification than the Artemia-fed larvae at Stages 7, 8 and 9 (pro- and climax metamorphosis), but this difference was significant only at Stage 8 (34.1%±2.56 SD vs. 31.9%±2.32 SD, P<0.05). Asymmetry of the cranium and consequently eye migration began earlier (Stage 7 vs. Stage 9) and was significantly better in the zooplankton-fed fish. The results suggest that nutritional differences in content of vitamin A and thyroid hormones, which target osteoblasts and osteoclasts, may underlie differences in developmental trajectory. The results also support the hypothesis of a critical window of metamorphosis between 14 and 25 days post start feeding in halibut larvae. [Copyright &y& Elsevier]

Abstract Fish fillet quality has been shown to be influenced by the level of antioxidants in preslaughter diet. Thus, an experiment was conducted to study the effect of different levels of vitamin E and C on the fillet quality of market-size reared turbot (Scophthalmus maximus ). Turbot of a mean initial weight of 347 ± 20 g were divided into four groups and fed commercial turbot diets (60% protein, 12% fat), supplemented with α -tocopheryl acetate (mg kg -1 ) and ascorbyl-2 monophosphate (mg kg -1 ) at the following dietary levels: 500/100, 1000/100, 100/1000, 100/100 respectively. Over a dietary supplementation period of 15 weeks, fish were fed to satiation and reached a final mean weight of 916 ± 29 g. α-Tocopherol levels increased significantly ( P < 0.001) in tissue (i.e. muscle, liver, heart and kidney) of fish fed diets containing elevated levels of α -tocopheryl acetate. In ice storage, fillets of these fish exhibited significantly lower ( P < 0.001) levels of lipid oxidation, and showed significantly less ( P < 0.001) colour deterioration (higher hue angle and lower chroma). Elevated dietary α -tocopheryl acetate levels had a negative effect ( P ≤ 0.001) on the concentration of ascorbic acid in muscle tissue. An increase in dietary vitamin C did not have any detectable effect on fillet quality. Prolonged feeding times had a negative effect on lipid oxidation ( P < 0.001) and colour deterioration ( P < 0.01). These results suggest that increased dietary α -tocopheryl acetate could prevent colour deterioration and lipid oxidation of turbot fillets in retail storage on ice. [ABSTRACT FROM AUTHOR]