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To understand the genetic basis of coping style in European seabass, fish from a full factorial mating (10 females x 50 males) were reared in common garden and individually tagged. Individuals coping style was characterized through behavior tests at four different ages, categorizing fish into proactive or reactive: a hypoxia avoidance test (at 255 days post hatching, dph) and 3 risk-taking tests (at 276, 286 and 304 dph). We observed significant heritability of the coping style, higher for the average of risk-taking scores (h2 = 0.45 ± 0.14) than for the hypoxia avoidance test (h2 = 0.19 ± 0.10). The genetic correlations between the three risk-taking scores were very high (rA = 0.96-0.99) showing that although their repeatability was moderately high (rP = 0.64-0.72), successive risk-taking tests evaluated the same genetic variation. A mild genetic correlation between the results of the hypoxia avoidance test and the average of risk-taking scores (0.45 ± 0.27) suggested that hypoxia avoidance and risk-taking tests do not address exactly the same behavioral and physiological responses. Genetic correlations between weight and risk taking traits showed negative values whatever the test used in our population i.e. reactive individual weights were larger. The results of this quantitative genetic analysis suggest a potential for the development of selection programs based on coping styles that could increase seabass welfare without altering growth performances. Overall, it also contributes to a better understanding of the origin and the significance of individual behavioral differences.

Partial or total replacement of fish meal by a mixture of plant protein (PP) sources (corn gluten, wheat gluten, extruded peas, rapeseed meal and sweet white lupin) balanced with indispensable amino acids was examined in juvenile gilthead sea bream over the course of a 6-month growth trial. A diet with fish meal (FM) as the sole protein source was compared to diets with 50%, 75% and 100% of replacement (PP50, PP75, and PP100). The possible influence of diets on growth performance, plasma metabolites, gut integrity, liver structure, anti-oxidant and immune status was evaluated. Final body weight was progressively decreased with PP inclusion, but in PP50 and PP75-fed fish, feed efficiency (FE) was significantly improved and specific growth rates remained unchanged or slightly reduced in comparison to fish fed the FM diet. In fish fed PP100 diet, FE remained unchanged and feed intake and growth decreased dramatically. In this group of fish, liver fat deposition was also largely increased, enterocytes showed an increased number of lipidic vacuoles and/or deposition of protein droplets, and the submucosa of intestine was dilated/hypertrophied and infiltrated with eosinophilic granular cells. Plasma glucose levels did not differ among the four groups, but a significant and progressive decrease of plasma cholesterol and plasma protein levels was found with FM replacement. The glutathione redox status in blood and liver increased with the increase of PP content and this increment was statistically significant in the liver of the three PP-fed groups. Glutathione reductase and gamma-glutainyl transferase were also enhanced by PP inclusion. Plasma lysozyme levels were not altered by the dietary treatment, but respiratory burst of head kidney leucocytes and plasma myeloperoxidase values were significantly increased in PP75 and PP100 fish, respectively. Complement (ACH(50)) was significantly increased in PP50 fed fish and decreased in PP75 and PP100 groups. As a general conclusion, substitution of FM by a mixture of PP sources exerted an anti-oxidative effect, compromised growth performance only at the 100% level, and decreased one of the immune defence mechanisms at above 75% level. (c) 2005 Elsevier B.V All rights reserved.

Related sib-groups of rainbow trout × brown trout and rainbow trout × brook charr triploid hybrids and monospecific diploid and triploid rainbow trout controls were obtained from a common set of rainbow trout dams. On the basis of hybrid juvenile performances, 10 sib-groups were selected and the corresponding diploid rainbow trouts were raised up to adult stage. Females from each group of rainbow trout were used to produce a second generation of hybrid progeny, the performances of which were analysed for grandmaternal variation and relation with first-generation relatives. Results showed that hybrid traits (alevin yield and weight, survival and growth of fingerlings) were strongly influenced by maternal origin, and could be correlated to those of rainbow trout controls, but that maternal abilities had a low rate of inheritance. It was concluded that little improvement can be expected through selective breeding within parental populations.

Two diets based oil fish meal (FM) or oil a mixture of plant protein sources supplemented with free amino acids (PP) were fed to rainbow trout having a mean initial body weight of 162.5 g reared at 17 +/- 1 degreesC for 24 weeks to evaluate the effect of plant protein sources oil fish growth, morphological and body quality traits. At the end of the growth study, samples were withdrawn for chemical analyses as well as measurements of different parameters of quality. Compared to the FM group, the trout fed diet PP had lower growth rates (mean final body weight 663 vs. 800 g), feed efficiency (0.95 vs. 1.07) and protein efficiency ratio (1.96 vs. 2.13). Trout fed diet PP were also characterised by a lower dressed weight (89.45% vs. 91.07%), hepato-somatic index (0.92% vs. 1.01%) and fillet lipid content (5.50% vs. 6.98%), but had a higher mesenteric fat (5.65% vs. 4.08%), viscero-somatic index (10.55% vs. 8.93%) and fillet crude protein content (20.53% vs. 19.93%). The muscle fatty acid composition reflected that of the diet with a higher level of polyunsaturated (n-6) fatty acids in trout fed diet PP and a higher content in polyunsaturated n-3 fatty acids and n-3/n-6 ratio in trout fed diet FM. Sensory analysis was carried out at 5 days post-mortem on microwave-cooked dorsal portions of fillets stored at 1 degreesC with ice covering. The results of the triangular test showed differences between groups (P

The present work aimed at evaluating whether solubility and peptide profile of dietary protein can affect survival and growth performance of common carp during early stages of life. Water-insoluble casein and two forms of soluble casein (non-hydrolysed and hydrolysed) were used as protein sources at different proportions in the experimental diets for first-feeding carp larvae. When provided as the only protein source water-insoluble casein led to high mortality and depressed growth after 21 days. The partial or total substitution of water-insoluble casein by soluble non-hydrolysed casein effectively improved survival and enhanced growth of larvae. An optimum level of soluble non-hydrolysed protein was found at 25% of total protein. The addition of some hydrolysed casein (25% of soluble protein) further improved results. However, high dietary levels of hydrolysed casein led to negative effects on larval performance, which would be related with a surplus of di-/tripeptides or/and amino acids. Protein solubility appears to have only a temporary effect on larval performance, probably related with the ontogeny of the digestive tract, since about 2 weeks after the onset of exogenous feeding larvae became able to use efficiently water-insoluble protein. Results also suggest the need for a balance in the peptide profile to optimise the utilization of dietary protein by fish larvae.

Five practical diets in which the supply of protein from fish meal was decreased gradually from 100% to about 2% and replaced by plant protein sources were formulated. European seabass weighing about 190 g were fed these diets for 12 weeks at a water temperature of 22 °C. Feed was dispensed using automatic self-feeders and voluntary feed intake (VFI) was closely monitored. We did not find any significant difference among diets in the apparent digestibility coefficients (ADC) of dry matter (80–82%), protein (94–96%), energy (88–92%) or phosphorus (49–58%). Replacement of fish meal by plant protein ingredients did not influence VFI. All groups had very good growth rates (DGI above 1.3%/day) and there were no significant differences in growth rate, feed efficiency or in daily nitrogen gains among groups. There was, however, a slight increase in fat deposition in fish fed diets with plant protein sources. Ammonia nitrogen and soluble phosphorus excretion rates were measured. Nitrogen and phosphorus balance studies indicated that fish meal replacement by plant ingredients led to a slight increase in nitrogen losses (from 83 to 103 g N/kg weight gain) but led to a significant reduction in total phosphorus losses (from 13 to 5 g P/kg weight gain). These results combined with the remarkable acceptability of diets containing high levels of plant protein ingredients with identical growth performances of European seabass show clearly that dietary fish meal levels can be considerably reduced without any adverse consequence in terms of somatic growth or nitrogen utilisation.

A 21-day feeding trial was carried out to investigate the ability of first feeding European sea bass larvae to utilize medium-chain triacylglycerols as an alternative source of energy. Three compound diets based on soluble fish protein concentrate and yeast were supplemented with either 3% tricaproin (TC6), tricaprylin (TC8) or tricaprin (TC10). A diet containing triolein (TOL) was used as a reference diet. Diets were tested on four replicate groups of first feeding European sea bass larvae at 20°C, i.e. 6 days after hatching. At the end of the 21-day trial, TC8 yielded significantly higher survival (57±8% vs. 28±11% for the three other groups). Considered together, larvae fed TC8 and TC6 displayed better growth rates than larvae fed TOL and TC10 (final mean wet weights: 1.5±0.3 mg vs. 1.2±0.2 mg, respectively). The fatty acid composition of larval total lipid revealed a low deposit of medium-chain fatty acids (between 1 and 3% of total fatty acids) suggesting that medium-chain fatty acids were oxidized for energetic purposes. Tricaprylin and to a lesser extent tricaproin, appear to be potential energy sources for first feeding European sea bass larvae reared on compound diets.

This study was performed to assess growth rate, feed efficiency, and N and P loss of sea bass (initial body weight 3.5 g), held in 500-l tanks under ambient temperature and natural light, and fed according to the following methods: by automatic feeders that released feed continually in daylight according to feed manufacturers' recommendations (AF100%); half of the above continually in daylight (AF50%); half of the above again but in two meals only (AF50%M); and by self-feeders that supplied feed at low (SFL), medium (SFM) and high (SFH) reward. None of the feeding conditions affected the survival rate of fish. SFL fish had the highest specific growth rate, while AF50% and AF50%M the lowest. Population weight distribution in the restricted automatic-fed fish (AF50% and AF50%M) was more homogenous compared to the other feeding conditions. These two practices produced high feed efficiency ratios (0.93 and 0.95, respectively), compared to the AF100% (0.57) and self-fed ones (SFL: 0.60; SFM: 0.37; SFH: 0.21). Self-feeding at low reward of 0.6 g trigger −1 could be considered as the optimum feeding practice, combining higher weight gain, lower N and P loss, and intermediate feed supply compared to the other treatments. In the SFH method, fish did not adjust their manipulation of the self-feeders according to their feed needs. Daily feeding activity in all self-fed fish groups was independent of feeding reward.

A 21-day feeding trial was carried out to investigate the ability of first-feeding carp larvae to utilize medium-chain fatty acids (MCFA). Six semi-purified diets, with a common casein and soluble fish protein concentrate basis, were tested on triplicate groups of 400 larvae. The diets were isolipidic (23–24% of dry matter). They differed only by triacylglycerol supplementation (10% of diet) which consisted of either triolein (TO), coconut oil (CO) or tricaprylin (TC) alone or in combination of two of these (TO+CO, CO+TC, TO+TC). Survival and growth rates of larvae fed with CO or TO were high (survival 95–97%, mean wet weight 60–67 mg after 21 days). Addition of TC (5 or 10% of diet) induced a significant mortality as early as 11 days of feeding and resulted in a final survival of less than 6%. TC also led to reduced growth rates (final mean larval weight 6–13 mg). The fatty acid (FA) composition of larvae fed with TO or CO reflected that of the diets with high levels of oleic acid (42% of total FA) in larvae fed with TO and lauric and myristic acids (17 and 10% of total FA, respectively) in larvae fed with CO. In contrast, larvae fed with TC contained only traces (0.3% of total FA) of caprylic acid but had higher levels of capric acid than other larvae (6% vs. 1–2%). Present results indicate an important difference in the utilization between MCFA supplied as CO (12:0) and TC (8:0).

Gilthead seabream were fed a fish meal based diet, supplemented with graded amounts of ascorbyl polyphosphate equivalent to 0, 25, 50, 100 and 200 mg of l -ascorbate (AA)/kg, for 12 weeks. Although there were no significant differences between growth rates of each group, the feed gain ratio and voluntary feed intake were significantly lower, and the protein efficiency ratio was significantly higher for the fish fed 200 mg AA/kg, when compared with the group fed 0 mg AA/kg. An increase of the ascorbate concentration within the liver and spleen occurred with the increasing vitamin supplementation. After 12 weeks, the fish were subjected to hypoxia for 24 h to determine the influence of AA supplementation on the physiological response to this stressor. A significant hyperglycaemia occurred in fish fed all the diets 3 h after the onset of stress, although a significantly higher resting plasma glucose was observed in fish fed the AA free diet. No significant difference was found in plasma cortisol concentration with stress, with the exception of fish fed the 100 mg of AA/kg diet, where a significantly lower cortisol level was found after 9 h of hypoxia. Fish fed the non-supplemented diet showed wider variation and a tendency to increase this variable, having significantly higher levels at 9 h and 24 h of stress then all the other groups and than fish fed the 200 mg AA/kg diet, respectively. Stress had no detectable effect on liver AA concentration in all groups. However, spleen AA showed significantly increased levels between 3–6 h of hypoxic stress in fish fed 25 and 200 mg AA/kg diet and a further increase after 9 h in fish fed the 200 mg of AA/kg diet. These results suggest that the ascorbic acid requirements for seabream is less than 25 mg/kg diet based on a 12-week growth study and that it requires about a four-field increase in weight before signs of deficiency can be observed. Also, the fact that no variation in liver vitamin C concentration was be detected as a response to stress, suggests that this kind of stress does not significantly increase the utilization of this vitamin. However, a possible relation between dietary ascorbate and the physiological response to hypoxia was found, since the fish receiving the non-supplemented diet showed increased plasma glucose and a tendency to have wider plasma cortisol variations than the fish fed the supplemented diets.

Histological observations were made in common carp larvae in order to understand the origin of the phospholipid (PL) requirement of fish during their young stages. Larvae were fed for 6 or 8 days after start-feeding on semi-purified diets containing peanut oil and supplemented with or without different PL fractions enriched in phosphatidylcholine (PC) or phosphatidylinositol (PI). A group of larvae was also fed Artemia nauplii. Dietary PL deficiency was associated with an accumulation of fat droplets in the enterocytes of the anterior intestine, an increase in height of mucosal epithelium, a reduced total liver volume and mean hepatocyte volume. In contrast, diet supplementation with PC from hen egg yolk or from soybean prevented the intestinal steatosis and resulted in larger liver volume and larger hepatocyte volume. Larvae fed Artemia showed the same features as larvae fed PC-enriched diets. Hydrogenated PC also prevented the intestinal steatosis but resulted in small liver and hepatocyte size. Larvae fed PI-enriched diets exhibited intestinal steatosis, although less systematically than larvae fed PL-deficient diets, and reduced liver and hepatocyte size. Results support previous opinions that PL are needed for the absorption of neutral lipids although their beneficial effect appears to be independent of their emulsifying properties. The limiting stage seems to be the synthesis and exportation of chylomicrons or very low density lipoprotein (VLDL) by the enterocytes and not the intraluminal formation of micelles. PC appears to have a specific role for chylomicrons and VLDL synthesis and secretion, as in mammals. The reduced liver and hepatocyte size in the absence of PC could result from a decreased energy supply due to poor lipid absorption.

International audience; The composition and seasonal dynamics of biofilm-associated eukaryotic communities were analysed at the metre and kilometre scale along a salinity gradient in the Westerschelde estuary (The Netherlands), using microscopy and a genetic fingerprinting technique (PCR-DGGE). Microphytobenthic biomass, measured as chlorophyll a (chl a), varied seasonally over 2 orders of magnitude, being highest in spring. Communities were dominated by epipelic diatoms, in particular by members of the genus Navicula. In spring, a few smaller epipelic diatom species dominated during biomass peaks, while during the rest of the year, communities were more diverse and were characterised by larger species. The microphytobenthic community collapsed when grazers appeared, which happened concomitantly with a rise in temperature. Spring biomass development was associated with marked changes in porewater nutrient concentrations, especially towards the estuary mouth. In the DGGE data, diatoms, ciliates, amoebae, copepods, nematodes, annelids and platyhelminthes were detected. Ordination analysis of the species counts and DGGE data were largely congruent and indicated that on the scale of the whole estuary (i.e. km scale), taxonomic turnover in microphytobenthos composition was mainly associated with the salinity gradient. At smaller spatial scales, the position of sampling localities along the tidal exposure gradient appeared to be the main determinant of species turnover, in particular in the brackish reaches of the estuary.

International audience; The aim of the study was to determine the influence of dietary phospholipid (PL) levels on survival and development of first feeding gilthead sea bream (Sparus aurata) larvae. Larvae were fed from day 4 to 23 posthatching with an isoproteic and isolipidic formulated diet with graded levels of PL from 90–150 g kg)1 dry matter (DM). A dietary PL content of more than 90 g kg)1 DM seems to be necessary for sustaining growth of first feeding sea bream larvae. The survival rates of larvae fed the formulated diets (31–40% at day 23) were similar to those generally observed in marine aquaculture hatcheries with live prey feeding sequence. However, this high survival rate was not associated with high growth and the larvae showed, at the end of the study, a high proportion of individuals with abnormal liver and calculi in the urinary bladder. It is concluded that although the diets used here cannot be used in total replacement of live preys, they constitute a solid starting point for further nutritional studies with first feeding gilthead sea bream larvae

Large yellow croaker is an important marine fish species for aquaculture in China. Larval rearing of this species is still based on live prey feeding. The aim of this study was to describe the onset and development of the main digestive enzymes during larval development of this species, in order to obtain essential data for the formulation of a compound diet adapted to larvae. Enzymatic assays were conducted from day I post hatching to day 40 in larvae fed the following live prey sequence: rotifers, Artemia nauplii, copepods, and then frozen copepods. Assays were done on whole larvae until day 19, then on dissected larvae and on purified brush border membranes of intestine. Pancreatic enzymes, amylase, and trypsin, showed high activities from early stages, even before mouth opening. Mechanisms of pancreatic secretion were achieved from day 19. Enzymes of brush border membranes, alkaline phosphatase, and aminopeptidase N, increased abruptly between day 23 and 25, showing maturation of the intestinal digestive process. These data, together with data describing mouth enlargement during development, suggest that large yellow croaker larvae could be fed successfully with a compound diet from early stages, at least from day 23.

Temporal changes in the bacterial community composition (BCC) and the impact of resources and predation on this community composition have been studied in the euphotic zone of the Sep reservoir (France), using terminal-restriction fragment length polymorphism (T-RFLP) and fluorescent in situ hybridization (FISH) for Eubacteria (EUB338) and eubacterial subgroups. Net growth and grazing rates of the various subgroups were computed from experiments conducted in dialysis bags in the presence or absence of predators. There was a significant difference between the grazing rates of different bacterial groups and subclasses, the alpha-proteobacteria (ALF1b) were subjected to the highest grazing rate (max. 1.76 d -1 ). In contrast, the beta-proteobacteria (BET42a) seemed to be little consumed by bacterivorous organisms, and predation led to large variations in the grazing rates of Cytophaga-Flavobacterium (CF319a). The different composition of bacterial con- sumers (Dinobryon sp. and Cladocera) during the study could explain the observed differences in grazing impact. The mean net growth rates of total bacteria, EUB338, BET42a ALF1b, and CF319a in dialysis bags without predators were 0.21, 0.69, 0.45, 0.50 and 0.84 d -1 , respectively. Various statisti- cal analyses indicated that the BCC could depend on the organic matter excreted by the phyto- plankton. There were also positive correlations not only between net growth and/or net production of ALF1b and CF319a with the primary production and biomass of the main phytoplankton groups, but also between phytoplankton biomass, primary production (PP) and some operational taxonomic units (OTUs). Among the physical variables, input and output of water in the reservoir seem to play a role in determining the BCC in this ecosystem. The results suggest that the BCC depends on the combined impact of dominant substrate sources and selective predation by bacterial consumers.

Triplicate groups of European sea bass juveniles (60 g) were fed for 84 days two experimental diets containing either vegetable or marine oil (0.4 and 2.2% n-3 highly unsaturated fatty acid [n-3 HUFA] dry matter in LD and HD, respectively) and held at 22 or 29 degreesC (LD-22, LD-29, HD-22 and HD-29 groups). Significant differences in mass gain between the two diets and temperatures were, observed from day 28 onwards, and on day 84, weight was 18% higher in the HD-29 group than in the LD-22 group (the highest and lowest values. respectively). Over the 84-day period-SGR was significantly affected both by temperatures and diets (P=6x10(-4) and 2x10(-4) respectively), averaging 1.01 and 1.07 in the HD-22 and HD-29 groups compared to 0.92 and 1.0 in the LD-22 and LD-29 groups. Differences in growth rate between the experimental conditions were mainly explained by differences in feed intake (FI). FI was more affected by temperature than by diets (in fish fed HD, it was 1.7% day(-1) at 29 degreesC and 1.4% day(-1) at 22 degreesC, and 1.1% day(-1) and 1.3% day(-1), respectively, with LD). Feed conversion ratio (FCR) was significantly affected by temperature and diets; days 0-84 FCR was on HD and LD 1.6 and 1.7 at 29 degreesC and 1-4-1.5 at 22 degreesC. Considering growth and feeding parameters. no interaction between dietary concentration in n-3 HUTA and temperatures were observed. In acclimated fish, MO2 on routine metabolism was the highest at HD-29 (396 mg O-2 kg(-1) h(-1)) as it was dependent on FI. There was no major difference in fish whole body composition, and protein retention was more affected by temperature than by diets. Diets and temperature affected polar lipid fatty acid content, without interaction; n-3 HUFAs were lower at 29 degreesC than at 22 degreesC. Fatty acids of total and neutral lipids (NL) were mainly affected by dietary fatty acids, while some low but significant influences of temperature were observed. Interactions between the two studied factors concerned particularly n-3 HUFAs content, lower at 29 than at 22 degreesC only in fish fed vegetable oil (LD). This study demonstrated that in high-quality sea bass juveniles, a 3-month deficiency in dietary n-3 HUFA did not drastically impair fish capacity to adapt to a high temperature, 29 degreesC.

Effects of porcine bile extracts added at three different dietary concentrations 0, 10 and 20 g kg-1 were studied on astaxanthin serum concentration in rainbow trout (mean weight 200 ± 7 g). Astaxanthin from micro-algae Haematococcus pluvialis and synthetic astaxanthin (CARO-PHYLL® pink) were incorporated in diets of rainbow trout at a rate of 100 mg astaxanthin kg-1 of feed. Fish were hand fed twice a day. After 5 days of feeding there was a significant effect of the pigment source on the ratio (total blood astaxanthin per unit body weight to cumulative astaxanthin intake per unit body weight). Trout receiving synthetic astaxanthin showed a significantly (P < 0.05) higher ratio than trout fed algal astaxanthin. Increasing dietary bile extract did not lead to produce any effect on this ratio. The power of the statistical analysis is discussed. Therefore, the interaction (pigment source x dietary bile concentration) showed no more effect.

Recent results have demonstrated that live yeast in diets improved gut maturation in sea bass larvae. In this study, we tested the absence and two levels of live yeast in sea bass larvae diets. Specimens were fed from time of mouth opening to 37 days after hatching a diet of 0%, 1.1%, or 5.7% wet weight of live yeast (Debaryomyces hansenii CBS 8339). Yeast incorporation improved survival 10%, and reduced malformed larvae. In groups fed 1.1% yeast, only 1% of larvae were malformed, compared to 14% in the control group. Final mean weight in groups fed 1.1% yeast was twice that of other groups. Activities and concentrations of mRNA trypsin and lipase were higher in the two groups fed yeast than in the control group, whereas activity and concentration of mRNA amylase were lower. This suggests that the pancreas matured faster in the two groups fed yeast. Activities of intestinal enzymes alkaline phosphatase, aminopeptidase N, and maltase in the group fed 1.1% yeast were higher than those in the two other groups, revealing earlier development of intestinal digestion. The best results were obtained with the diet containing 1.1% yeast cell biomass, corresponding approximately to 10(6) CFU g(-1) in the diet and 1.1 x 10(4) CFU per larva 30 days after hatching. The dose-dependent effect of yeast on rearing performance could be attributed to the amount of polyamines secreted by live yeast in the gut lumen of larvae.

Three practical isoproteic (54% protein) diets were formulated to contain graded levels of crude fat (diet L: 10%, diet M: 20% and diet H: 30%). Each diet was assigned unrestrictedly to three and restrictedly to two replicate groups of fish (IBW 243 g). In unrestricted groups, increasing the dietary lipid level led to a significant decrease in voluntary feed intake without affecting growth rate. In the feed-restricted groups, daily growth rates increased with increasing dietary fat levels. There was a significant and inverse effect of the dietary fat content on whole body moisture and fat levels, with highest lipid (ca. 20%) and lowest moisture (ca. 58%) contents in sea bass fed diet containing the highest lipid level; muscle lipid concentration was however not affected. Nitrogen retention was significantly increased by an increase in lipid concentration in the diets, with better efficiencies observed in unrestricted (ca. 31%) than in restricted groups (ca. 27%). Nitrogen loss was significantly affected by both the feeding level and the diet composition, with lowest values (ca. 60 g kg −1 ) in groups fed diet H unrestrictedly and highest values (ca. 90 g kg −1 ) in groups fed diet L at a restricted level. Soluble phosphorus excretion in H groups was less than half that in L groups, regardless of the feeding level.

Partial or total replacement of fish meal by a mixture of plant protein sources (corn gluten meal, wheat gluten, extruded peas, rapeseed meal) balanced with indispensable amino acids (IAA) was examined in juvenile gilthead sea bream (Sparus aurata) over the course of a 12-week growth trial. A diet with fish meal (FM) as the sole protein source was compared to diets with 50%, 75% and 100% of replacement (PP50, PP75, PP100). Protein retention was improved with more plant protein supply, and just a slight decrease in the final weight gain was found in fish fed PP50 and PP75 diets. However, in the PP100 group, weight gain was depressed up to 30% mainly as the result of a marked reduction of feed intake. These fish also showed a lower fat gain along with a marked hypocholesterolemic effect. Dietary treatment did not alter the hepatic activity of amino acid catabolising enzymes (alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), glutamate dehydrogenase (GDH)), although the size of the total muscle free amino acid (FAA) pool was increased by more plant protein supply. The activity of the somatotropic axis also varied among experimental groups, and the up-regulation of circulating growth hormone (GH) levels with a high plant protein supply followed the decrease in growth rates, plasma levels of insulin-like growth factor-I (IGF-I), and liver mRNA transcripts of IGF-I and GH receptors. This catabolic feature evidenced a liver desensitisation to the anabolic action of GH in the PP100 group, and to a lesser extent in the PP75 group. Taken together all these findings, up to 50-75% of fish meal replacement seems to be feasible with IAA supplementation, but further research is needed to fully identify the responsible factors for the depressed feed intake in order to achieve a full replacement in a fish species having high dietary protein requirements.

In the present study, we report the characterization in European sea bass of the partial cDNA sequences of three nuclear receptors, retinoic acid receptor (RAR)α, RARγ, retinoid X receptor (RXR)α, involved in retinoid pathways. These pathways participate to vertebrates morphogenesis processes and may be responsible for the appearance of skeletal malformations. The predicted polypeptide encoded by each cDNA sequence contains the ligand-binding domain (LBD) characteristic of nuclear hormone receptors, and the RXRα cDNA sequence also includes a partial zinc finger domain corresponding to the DNA-binding domain (DBD) of this receptor. The relative expression levels of the three receptors were determined by real-time polymerase chain reaction (RT–PCR) in European sea bass larvae. Between 10 and 42 days posthatch (dph), the expression of RARα and RARγ increased 7.3- and 35.6-fold, respectively, while RXRα expression was down-regulated with a factor of 35.4. The same trend was observed between 10 and 21 dph but was not statistically different. Using RNA/RNA hybridizations, RARα antisense probes were revealed in jaws at 5 dph, and, at 37 dph, they were detected in jaws, vertebra, liver, muscle, pectoral fins, brain, neural tissues, eyes, and branchial arches. At 37 dph, RARγ expression was found in the cartilage, eyes, and operculum, while the presence of RXRα mRNA was localised in the exocrine pancreas, liver, thyroid, kidney, heart, jaws, and teeth. These results suggested that RARα and RARγ were used for European sea bass development. RARγ would play a key role in the morphogenesis of the cephalic region, while RXRα would be essential during the early stages of development in European sea bass larvae when an intense process of differentiation occurred.

Males of Pangasius bocourti (3.3–6.9 kg) raised in floating cages on the Mekong River were used to study the production of milt and its use for fertilization. Although spontaneous spermiation occurred in mature males, the average volume of collected milt was low (26.5 μl kg −1 ). A single human chorionic gonadotropin (hCG) injection (2000 IU kg −1 ) induced a 13-fold increase in sperm volume, 12 h after injection (344.5 μl kg −1 ). The associated sperm concentration and production were 26.9×10 9 spz ml −1 and 8.4×10 9 spz kg −1 , respectively. Injection of GnRHa (30 μg kg −1 ) with domperidone (3 mg kg −1 ) induced a lower increase of sperm volume and sperm production. The motility of spermatozoa (spz) in well water lasted only 57 s, but was doubled in low saline solution (NaCl 34 mM). Crude milt could not be stored but five-fold dilution in immobilization solution (NaCl 207 mM) allowed fertilization to be postponed for 36 h. Fertilization was triggered by well water with milt diluted 1000 times.

The solubility of protein nitrogen at pH 8 in the organisms used as live food for fish larvae (rotifers and Artemia) was determined and the molecular weight profile of soluble protein nitrogen was analysed by HPLC-gel filtration chromatography. Soluble nitrogen accounted for 61% of total nitrogen in microalgae-fed rotifers, 47% in starved rotifers and 54% in newly hatched Artemia. A remarkable similarity in the profile of molecular weight distribution of soluble nitrogen was noticed among these three types of live food. The molecular weights of soluble nitrogen was partitioned as follows, respectively, in rotifers and Artemia: 84–88% and 89% >500 Da (corresponding mainly to proteins, poly- and oligopeptides), 8–11% and 4% from 200 to 500 Da (corresponding mainly to di- and tripeptides), 3–4% and 7%

Survival, growth, nitrogen (N) and phosphorus (P) budgets and feeding behaviour were studied in groups of sea bass, Dicentrarchus labrax L., that fed using self-feeders with different feed reward and maintained at different densities (up to 35 kg m−3 or 500 fish tank−1). The experiment was conducted in 500-l indoor tanks under ambient conditions of light and temperature during two successive years. In the first year (experiment I), fish (5.5±0.1 g) were separated into five groups according to stocking density (50, 200 or 500 fish tank−1) and reward (R=0.6 g trigger−1) level: 50:R, 200:R, 200:4R, 500:R and 500:10R. Both increases in stocking density and in feed reward affected negatively all the studied parameters concerning growth and feed efficiency (FE). In the second year (experiment II), the experiment was repeated with fish of similar weight (5.3±0.0 g), which were held under the following four feeding protocols: 50:0.5R, 50:R, 500:0.5R and 500:R. The lowest feed reward fish groups presented better tendencies in growth and feed efficiency independent of stocking density. Survival was high in all feeding regimes in both experiments, but at high density (500 fish tank−1), some mortalities (

During a field mesocosm experiment conducted in coastal waters off western Norway, 11 m3 enclosures were filled with unfiltered seawater and enriched daily with different nitrate and phosphate concentrations in order to induce a bloom of the coccolithophorid Emiliana huxleyi under different nutrient regimes. Flow cytometry (FCM) analysis was performed 5 times d-1 in order to follow the initiation, development and termination of the bloom as well as the production of large virus-like particles (LVLPs) identified as E. huxleyi viruses (EhV). EhV production was observed first in the enclosure where N was in excess, and P limitation induced a lower burst size compared to nitrate-replete enclosures. These observations suggest a critical role for both P and N in E. huxleyi-EhV interactions. Concomitant to EhV production, a shift was observed between the original population (coccolith-bearing cells) towards a population characterized by the same chlorophyll a (chl a) fluorescence but with lower right angle light scatter values. This population is likely to correspond to either senescent cells losing their coccoliths or cells characterized by a lower production of coccoliths possibly due to viral infection. At the end of experiment, a significant proportion of E. huxleyi had survived after the end of the bloom. This suggests either the presence of a resistant form of the coccolithophorid or a change in the dominance of different host and/or viral strains during the bloom. A periodical pattern in virus production was recorded with virus number decreasing during the second part of the day suggesting that virus production may be synchronized to the daily light cycle. Our results provide new insights towards the understanding of the relationship between a key marine species and its specific virus.

Three isoproteic (crude protein content: 56%) diets with different fat levels (11%, 20%, and 26%) were fed to triplicate groups of triploid brown trout (initial average body weight of 1.5 kg), reared in seawater. At the end of 3 months of feeding, fish fed the high-fat (HF) diet were split into two groups: a triplicate group of fish received the low-fat diet and another triplicate group was kept unfed for a further 2-month period. Fish initially fed the low-fat diet during the first period were continued to be fed the same diet. Fish fed the medium-fat (MF) diet during period 1 were eliminated for period 2. At the end of each period, comparative whole body analyses, sensory and instrumental (texture and colour) analyses were made on fresh and smoked fillets. During the first period, increasing dietary fat level had no significant effect on growth or feed utilisation, but increased whole body (14.6% to 17.9%, on wet weight basis) and muscle (8.3% to 11.0%) fat content. During the second period, the fish fed the low-fat diet had similar growth performance irrespective of previous nutritional history, whereas starvation led to significant loss of weight and fillet yield. Whole body fat content did not differ between groups (around 15%) at the end of period 2. In fish initially fed the HF diet, both starvation and feeding a low-fat diet led to a reduction in muscle lipid content. Sensory analyses revealed few differences between treatments, in terms of visual colour aspects, for both cooked and smoked fillets at the end of period 1. A positive relationship between instrumental colour analyses (L*, a*, b* values) and dietary fat levels was observed, but no difference was observed for instrumental texture measurements. At the end of period 2, a significant increase in parameters of colour was observed in unfed fish. Although both feed withdrawal and feeding a low-fat diet 2 months before slaughtering led to a reduction in fat content, starvation had the disadvantage of leading to significant weight loss.

The seabass, Dicentrarchus labrax L., is a leading species in European marine aquaculture, but its genetic characteristics necessary to set up breeding programmes are still unknown. New tools, such as genomic markers, now allow to carry out strain testings and estimations of genetic parameters in reasonable scale experimental facilities. However, because of the high cost of genotyping, the total number of fish to be measured will be limited and mating designs (type of cross, number of sires and dams) must be optimised. An optimisation trial is done in this study by simulation of a quantitative trait for two different strains of fish according to a polygenic model with additive, dominance, maternal and residual effects. The phenotypic coefficient of variation and the difference between crosses means (D=10%) were also included in the model. For technical limitations due to the species, the mating design chosen was a factorial cross between sires of both strains with dams from one strain (topcross). Different combinations of size of progeny sample (500–4000), number of sires (10–120/strain) and dams (4–16) were studied. Various mixed models (SAS®, proc Mixed, option REML) were used to estimate D, the power for detecting D, heritability (h2) and their standard error (S.E.) over 1000 repetitions. Incomplete factorials were also tested as well as the effect of differential survival between dam families. In strictly additive models (no dominance or maternal effects), D and h2 estimates were unbiased. The number of dams did not noticeably affect the precision of estimates, whatever the number of sires. A joint optimisation of sample size and number of sires led to a consensus value of 40 sires/strain with a sample size of 2000 progenies, which gave good precisions for D and h2. It was also shown that a mixed model (fixed strain effect+random sire effect) gave more accurate results than a simple fixed model (strain effect only). The inclusion of maternal and dominance effects did not markedly bias nor affect the precision of D and h2 estimates in a full factorial design, but could lower the precision (up to 40% increase S.E.) in incomplete factorial design. Variance in dam family sizes (due to differential survivals) did not affect the results in full factorials when set at values observed in seabass. It is then concluded that a factorial cross of 40 sires/strain with 8 dams and a sample size of 2000 progenies (on average 1000/strain) is appropriate for comparing seabass strains (power >0.8 for detecting a 20% difference between strains means) and jointly estimating heritability.

The relationship between specific growth rate and initial body weight in fish was analysed by multivariate analysis using data sets from growth studies on rainbow trout (initial weight between 10 and 30 g, n =546) and Atlantic salmon (initial weight between 10 and 20 g, n =355). We demonstrate that individuals can be pooled into different classes according to their growth characteristics. Classes with similar initial mean weight can have very different mean specific growth rate. Indeed, we found the mean specific growth rate ratio between classes with similar initial mean weight to be between 1.5 and 5.8 in rainbow trout and between 1.2 and 1.9 in Atlantic salmon. We conclude that the constitution of replicates with homogeneous initial weight is not assurance of homogeneous specific growth rate among replicates. The consequences of such variability in growth on experimental designs and power of analysis-of-variance models are discussed.

Although antimicrobial drugs testing and minimal inhibitory concentration (MIC) assessment have become of common use for guiding bacterial disease treatments, it soon appeared that temperature conditions under which tests were performed could result in strong variations and cause misinterpretations. This is specially inconvenient with fish pathogenic bacteria, many of which require low temperature incubation and do not fit easily with the standardized procedures generally accepted in medical laboratories. Temperature may affect both antimicrobial drugs and bacterial physiology through a variety of mechanisms such as stability and diffusion kinetics of the drug species, growth rate, membrane properties, enzymatic activity and genetic regulations of the bacterial cells. Interference and combination of so many effects make any prediction unrealistic. In MIC studies, however, dilution methods appear much less susceptible than diffusion methods to temperature-induced fluctuations. Provided interpretation is done carefully they should always be preferred to perform routinely antimicrobial tests.

Rainbow trout (8.5–9.5 g) of two strains (C and M) differing in growth potential were compared with respect to feeding motivation and feeding rhythms, over a 65-day experimental period, employing self-feeding or automatic feeding. Growth rate, feed gain ratio, feed intake and pattern of feeding activity of fish fed with self-feeders, were recorded, as was body composition of both strains. The final weight of fish of the fast-growing strain, strain C, fed using self-feeders, was significantly higher (82.6 g) than that observed for fish of the slow-growing strain, strain M (69.3 g). When the automatic feeders were used, no significant differences were found between the strains in terms of body weight gain (65 g). Results observed for feed gain ratio were also similar between the two strains. Although the voluntary feed intake (VFI) did not vary significantly with the genetic origin of the fish, strain C displayed a consistently higher VFI compared to strain M. The retention efficiency of nutrients and energy were similar between strains but significantly different between feeding systems. With regard to body composition, when fish were fed by means of self-feeders, no significant differences were found between the two rainbow trout strains. However, when fed automatically, dry matter and lipid content were highest in the strain M fish. The energy and protein content of the whole fish were not significantly influenced either by the feeding system or by the strain of the fish used.

A study was undertaken with marketable size turbot to evaluate the effects of dietary fat levels on chemical composition. lipogenesis and flesh quality, Four experimental diets containing graded levels of fish oil in order to obtain 10%, 15%, 20% and 25% of crude fat were fed to triplicate groups of turbot (initial body weight of 660 g) for 12 weeks in full strength seawater at temperature of 17 degreesC. Nutrient digestibility was not influenced by dietary fat levels. The best growth performance was observed in fish fed 10% and 15% dietary fat. High dietary lipid levels led to higher fat deposition in whole fish, although lipid level in muscle remained low (1.1% in dorsal muscle and 1.7% in ventral muscle irrespective of diet), Significant subcutaneous fat accumulation was detected in turbot. No protein sparing effect by lipid was observed in turbot fed high dietary fat. Hepatic lipogenic enzymes (glucose-6-phosphate dehydrogenase, G6PD; malic enzyme, ME and acetyl CoA carboxylase) did not show any dear change in activity in response to dietary fat content. With regards to quality parameters, there were no differences in gutted and fillet yields among treatments. Sensory analyses of dorsal fillets indicated only a difference in exudation (corresponding to loss of water) and whiteness within treatments in accordance with instrumental colour analyses and on ventral fillets, only a difference of sweet flavour was observed. No differences in hardness were detected by either instrumental texture analysis or sensory analysis. In conclusion, although high dietary lipid levels affected growth and whole body composition of turbot adversely they induced very few alterations in flesh quality.

Apparent digestibility coefficients (ADC) of nutrients and energy of extruded peas, extruded lupin and rapeseed meals were determined in juvenile rainbow trout and turbot. Extruded lupin was found to be a promising substitute for fish meal in the diets of trout and turbot, with an acceptable digestibility of its dry matter (70% in trout and 81% in turbot) and a high digestibility of its protein (96% in trout and 98% in turbot) and its energy (77% in trout and 85% in turbot). Extruded peas had a lower digestibility of its protein in trout (88%) than in turbot (92%), and the ADC of energy, mainly supplied as starch, was relatively low (69% in trout and 78% in turbot). The digestibility of rapeseed meal was improved by a thermal treatment. Without thermal treatment, rapeseed meal had a low digestibility of its dry matter (57%) and energy (69%) in turbot. The availability of phosphorus was higher for extruded lupin (62% in trout and 100% in turbot) compared to the other plant-ingredients. When compared to a solvent-extracted meal, the availability of phosphorus from rapeseed meal was improved by heat treatment in both species (42% vs. 26% in trout and 65% vs. 49% in turbot).

An experiment was conducted in order to assess the incorporation in diets for juvenile turbot of extruded lupin (Lupinus albus) and heat-treated (RM1) or untreated (RM2) rapeseed meals (Brassica napus) (26 and 40 mu mol glucosinolate/g DM, respectively). The level of incorporation of 30% for each plant-protein, as well as 46% for RM1 and 50% for lupin was tested and compared with a fish meal based control diet. Triplicate groups of turbot (initial body weight of 66 g) were fed by hand with isonitrogenous and isoenergetic experimental diets, twice daily and to visual satiety, during 63 days. Extruded lupin can be incorporated in diets of turbot up to a level of 50% without adverse effects on growth performance and body composition. Rapeseed meal can only be incorporated at levels up to 30%, but a preliminary heat treatment of RM is necessary in order to improve its nutritional quality. In turbot-fed the RM-based diets, plasma T(4) levels were reduced with low dietary content in glucosinolate breakdown products (3.6 mu mol/g), but no decrease in plasma T(3) levels was observed with the higher level of toxic compounds (4.4 mu mol/g). A significant deiodinase type II compensatory effect, leading to an increase of the conversion of T(4) to T(3), was observed in vitro in the liver of turbot fed RM1-based diets. The intake of lupin-based diets also had an effect on thyroid status with an increase of plasma T(3) levels and of deiodinase type I activity in liver and kidney, suggesting an increase in the degradation of rT(3) and in the conversion of T(4) to T(3).

The present study investigated the interaction of dietary medium-chain fatty acids (MCFA) and phospholipids (PL) on survival, growth and lipid metabolism in common carp larvae. Nine diets based on casein and dextrin and with a variable lipid part were tested in triplicate for 22 days post first feeding. The 3×3 design consisted of three triacylglycerols (3% of diet) combined with three different lipid supplements. Tested triacylglycerols were triolein (TOL), tricaprylin (TC8) and tricaproin (TC6), and lipid supplements were 2% soybean oil (low-fat diets without PL), 2% soybean lecithin (low-fat diets with 2% PL) or both 2% soybean lecithin and 6% TOL (high-fat diets with 2% PL). In the first step, both TC6 and TC8 resulted in improved survival and growth rates compared to TOL, irrespective of the PL supply. In the second step, TC8 decreased survival and growth rates, whereas the difference between TC6 and TOL became less. Histological signs of impaired intestinal absorption of neutral lipids were evidenced in larvae fed TOL without PL and also in high-fat diets with 2% PL. The latter diets also resulted in poorer growth rates compared to low-fat diets with 2% PL. These results suggest that the quantitative PL requirement of larvae increases as the dietary level of long-chain triacylglycerols increases. Larvae fed TC6 or TC8 showed enlarged liver and hepatocyte volume and a decreased level of body neutral lipids. Based on β-hydroxybutyrate (β-HBA) measurements in whole larvae, TC8 was found to be more ketogenic than TC6. TC6 and TC8 affected differently the fatty acid profile of larval body neutral lipids. TC6 did not induce the appearance of MCFA, whereas TC8 feeding resulted in a low level of 8:0 and relatively high levels of 10:0 (3.8% of total fatty acids). Neither 8:0 nor 10:0 were found in larval polar lipids. This study confirmed the essentiality of PL in common carp larval diets and underlines differences in the utilization of TC6 and TC8, which both initially stimulate growth during the first week, but only temporarily in the case of TC8.

A recombinant yeast system highly and stably expressing rainbow trout oestrogen receptor (rtER) was used in parallel with a more elaborated biological system, trout hepatocyte aggregate cultures to examine the oestrogenic potency of several chemicals commonly found in the environment. In hepatocyte cultures, the vitellogenin gene, whose expression is principally dependent upon oestradiol, was used as a biomarker. Moreover, competitive binding assays were performed to determine direct interaction between rtER and xenobiotics. This paper describes high specificity of our systems for screening potentially oestrogenic chemicals and determining the mode of action of trout ER with oestrogenic compounds. This work also demonstrates that it is important to combine bioassays with in vitro approaches to elucidate the mechanism of xenooestrogen actions.

Astaxanthin concentration in the blood of rainbow trout was studied in a feeding trial with two different astaxanthin sources: green algae Haematococcus pluvialis and commercial beadlets of 8% astaxanthin content (CAROPHYLL® Pink), and two different dietary lipid levels. The green algae contained 1.4% of carotenoids on a dry matter basis: free astaxanthin (< 1%), astaxanthin monoester (24.3%); astaxanthin diester (70.2%) and lutein (4.8%). Algal biomass was mechanically ground to disrupt the cell wall before incorporation in the feed. Hydrolysis of astaxanthin esters from algae occurred during the pelletization even at a low process temperature (43°C). Rainbow trout with an initial mean body weight of 150 g were fed experimental diets supplemented at a rate of 100 mg pigment/kg diet combined with two different lipid levels (9 and 24%) during 5 days. Astaxanthin concentration in the serum ranged from 5.3 μg/ml (8.9 nmol/ml) to 9.0 μg/ml (15.1 nmol/ml). Astaxanthin concentration in the serum was higher for fish fed high lipid level diets, independently of the astaxanthin source. No differences in the astaxanthin serum concentration were found for fish fed diets supplemented with either natural or synthetic astaxanthin, respectively 9.0 ± 1.9 and 8.4 ± 2.4 μg astaxanthin/ml serum, when dietary lipid level was high (24%). On the other hand, there was a higher blood astaxanthin concentration in fish fed diets supplemented with algal biomass (7.0 ± 2.4 μg astaxanthin/ml serum) compared to synthetic astaxanthin (5.3 ± 2.0 μg astaxanthin/ml serum) when dietary lipid level was low (9%).

The research of probiotics for aquatic animals is increasing with the demand for environment-friendly aquaculture. The probiotics were defined as live microbial feed supplements that improve health of man and terrestrial livestock. The gastrointestinal microbiota of fish and shellfish are peculiarly dependent on the external environment, due to the water flow passing through the digestive tract. Most bacterial cells are transient in the gut, with continuous intrusion of microbes coming from water and food. Some commercial products are referred to as probiotics, though they were designed to treat the rearing medium, not to supplement the diet. This extension of the probiotic concept is pertinent when the administered microbes survive in the gastrointestinal tract. Otherwise, more general terms are suggested, like biocontrol when the treatment is antagonistic to pathogens, or bioremediation when water quality is improved. However, the first probiotics tested in fish were commercial preparations devised for land animals. Though some effects were observed with such preparations, the survival of these bacteria was uncertain in aquatic environment. Most attempts to propose probiotics have been undertaken by isolating and selecting strains from aquatic environment. These microbes were Vibrionaceae, pseudomonads, lactic acid bacteria, Bacillus spp. and yeasts. Three main characteristics have been searched in microbes as candidates to improve the health of their host. (1) The antagonism to pathogens was shown in vitro in most cases. (2) The colonization potential of some candidate probionts was also studied. (3) Challenge tests confirmed that some strains could increase the resistance to disease of their host. Many other beneficial effects may be expected from probiotics, e.g., competition with pathogens for nutrients or for adhesion sites, and stimulation of the immune system. The most promising prospects are sketched out, but considerable efforts of research will be necessary to develop the applications to aquaculture.

A factorial experiment was conducted for 7 weeks over the summer period (23–26°C) with gilthead sea bream fingerlings fed under restricted (1–1.75%) and unrestricted (2.5–3%) conditions with two practical diets (55% protein–9% lipid; 46% protein–17% lipid). Specific growth rates ranged from 0.65 to 2.3%, and no significant differences were found at a given feeding level between dietary treatments. At the highest feeding level, no significant differences in the viscerosomatic, hepatosomatic and mesenteric fat index were observed, although the daily fat gain was always higher in fish fed the 17% lipid diet. Under restricted feeding conditions, no significant differences in daily N gain were found. However, in fish fed to visual satiety, N gain was significantly lower in fish fed the lipid enriched- diet. Thus, when considering protein retention, a reliable protein sparing effect of dietary lipid was only found under restricted feeding conditions, where a feed gain ratio near to 1 was found with both diets at the intermediate ration size (1.75%). Plasma growth hormone (GH) levels decreased with the increase of ration size. Besides, under fixed feeding levels, plasma GH levels were lower in fish fed the high lipid diet. An opposite trend was found in fish fed to satiety. After 8 days of fasting, fish previously fed the 17% lipid diet to satiety also exhibited a more pronounced hypersomatotropism and hypoglycemia, linked to increased loss of body fat. As a practical consequence, when high fat diets are used, these findings show the need to optimize ration size to avoid unwanted adiposity and impaired growth performance in gilthead sea bream.

Trials were conducted to determine whether the recent National Research Council [NRC (National Research Council), 1993. Nutrient requirements of fish. National Academy of Sciences, Washington, DC, USA, 114 pp.] data on the vitamin requirements of rainbow trout are (1) sufficient for salmonids fed practical diets, (2) applicable with semipurified diets containing all vitamins at the recommended levels only and with safety margins, and (3) applicable to other selected species of finfish. In the first trial, diets with either semipurified ingredients (diets 1 to 5) or practical ingredients (diets 6 to 8) were hand-fed to near satiety to triplicate groups of rainbow trout (IBW: 2.8 g; 15°C) over a period of 12 weeks. The supply of all vitamins was adjusted to be either at least meeting the NRC (1993) recommended levels (diets 3, 5, 7 to 8) or much above (diets 1, 4, 6). Results showed that while the NRC (1993) requirement levels were adequate as supplements when rainbow trout were fed practical diets, the same level led to depressed growth performance and nitrogen utilisation in those fed semipurified diets. In a second trial, triplicate groups of chinook salmon (IBW: 9.8 g; 12°C; 16 weeks), were fed semipurified (diets 1 to 4) or practical (diets 5 to 8) diets with graded levels of a vitamin mixture at the NRC recommended levels (100 to 200% and 50 to 125%, respectively). In this species, growth performance and feed utilisation were little affected by the dietary treatments. In two further trials, semipurified or practical diets supplying all vitamins at or above the recommended levels were given to European sea bass. Results confirm the applicability of the NRC recommendations for salmonids also for the seabass fed practical diets, but with semipurified diets, modest safety margins would appear necessary for rainbow trout and seabass with high growth rate.

Two groups of Dicentrarchus labrax were reared from day 5 to day 20 post-hatching with live prey in running seawater with or without algae. The concentration of algae Isochryisis galbana was maintained between 20 000 to 40 000 cells ml−1. On day 20, each group was divided into two subgroups, one still receiving live prey, the other fed a compound diet until day 32. On day 32, larvae fed live prey in the presence of algae exhibited an 18% higher survival than larvae reared without algae; in group fed compound diet, the algae supply induced a 26% survival enhancement. At day 16, it was observed a 40% weight improvement in the group reared in the presence of algae compared to the group reared without algae. At day 32, a slight but significant positive effect of algae on larvae weight was still noted in the group fed compound diet. From day 8 to day 16, the presence of algae in the rearing water resulted in an increase in trypsin activity whereas amylase and chymotrypsin were not affected. At day 26, alkaline phosphatase and maltase assayed in purified brush border membranes of intestine were significantly higher in larvae reared in seawater with algae than in those reared in clear water. This result suggests that the presence of algae facilitates the onset of hydrolytic functions of cell membranes. The significant improvement in survival of larvae reared in the presence of algae was related to the early development of brush border membranes. It is concluded that the algae acts by triggering digestive enzyme production, at both the pancreatic and intestinal level.

Microsatellite markers isolated from a genomic library of sea bass, Dicentrarchus labrax, were used to assess parentage in a breeding programme. The progenies were obtained from a complete factorial design between three males and three females, and mass-reared in a single tank. Three samples of 329, 97 and 360 larvae respectively aged 11, 40 and 116 days-old, were genotyped with microsatellite loci. The parentage of all individuals was determined unambiguously with only two microsatellite loci. A genetic analysis of quantitative characters (survival, body weight, length and malformation, condition coefficient) was realized on the larvae identified in this way. Each of the families appeared significantly different for the analyzed traits. We argue that microsatellites will be a valuable tool in: (i) breed identification (ii) family selection programs in which genetic tagging will allow different genotypes to be reared together, thus greatly reducing the impact of environmental variance and the number of replicate needed ponds.

Three compound diets, based on fish protein hydrolysate and yeast (diet A), soybean protein concentrate and yeast (diet B) and fish meal (diet C), were tested with start-feeding sea bass and carp larvae, during 28 days at 19°C (4 replicates) and 20 days at 24°C (3 replicates), respectively. In sea bass larvae, diet A yielded better results (survival: 35±6%, mean weight: 3.4±0.8 mg) than diets B (survival: 14±2%, mean weight: 1.8±0.4 mg) and C (survival: 19±5%, mean weight 1.1±0.2 mg). In carp larvae, feeding diet A resulted in a high survival (86±7%) and the best growth (mean weight: 73±14 mg), diet B led to in a higher survival (98±1%) but to a lower growth (mean weight: 45±12 mg) and diet C gave the poorest survival (45±6%) and mean weight (11±1 mg). Thus, start-feeding sea bass larvae proved to be able to utilize compound diets, as previously shown in carp and other freshwater fish larvae. Although inferior to live food, diet A containing fish protein hydrolysate supported significant growth and survival and can serve as a starting point for further study of the nutritional requirements of sea bass larvae.

As some controversy seem to exist regarding the dietary essentiality of ascorbic acid (AA) for larval cyprinids, a study was conducted to determine the dietary AA requirements with first-feeding larvae of common carp. Six semi-purified diets were formulated to contain graded levels (0, 10, 30, 90, 270, 810 mg kg −1 ) of AA supplied as ascorbyl polyphosphate. Triplicate groups of 250 larvae each were fed one of the experimental diets using automatic feed dispensers over the light hours of the day (temperature: 24±1°C; photoperiod 16L:8D). A duplicate group was kept unfed. Survival, body length and weight increments were recorded. At the end of the 21 day trial, samples were withdrawn for analyses of whole body vitamin C content. The results indicate that common carp larvae have a dietary requirement for ascorbic acid. The required level for maximum tissue storage is higher than that needed for survival and maximum growth. Based on growth performance, a dietary requirement of about 45 mg AA equivalent kg −1 was established. Maximal body vitamin C concentration (104–115 μ g g −1 wet weight) was observed in larvae fed 270 mg AA equivalent kg −1 or more.

Growth responses of rainbow trout fed on demand using self-feeders were tested over an 8 week period when triplicate groups were exposed to two feeding levels (unlimited and fixed ration), at two feeding frequencies (time-restricted and free access) and three reward levels (0.17 g, 0.30 g and 0.43 g per trigger actuation). Triplicate groups were also hand fed as control of maximum growth. Each fish was marked according to its weight-class, and each group of 26 fish comprised a predetermined number of fish per weight-class: two fish of 13–16 g, six fish of 16–19 g, 10 fish of 19–22 g, six fish of 22–25 g and two fish of 25–28 g. There was no significant effect of feeding regime on feed efficiency. Voluntary feed intake and specific growth rates were significantly decreased as fish were exposed to reduced reward levels, even though there was a negative relationship between reward level and daily demand. Time-restricted access to self-feeders led to a decrease in feed intake, and an increase in growth heterogeneity in comparison with free access to self-feeders. Voluntary feed intake and specific growth rates were always lower in self-fed groups than in groups fed to apparent satiation by hand. Individual growth heterogeneity was greater within tanks allowed time-restricted access to self-feeders and within tanks fed by hand to visual satiation than within those given continuous access to self feeders. It is suggested that rainbow trout fed on demand with self feeders may not ingest as much food as they would be able to, and may not be satiated, but do express their hunger in relation with the level of effort that has to be done to obtain food.

Fish are continuously exposed to a wide range of microorganisms present in the environment, and the microbiota of fish have been the subject of several reviews. This review evaluates lactic acid bacteria in fish, and focuses on the several investigations that have demonstrated that Streptococcus, Leuconostoc, Lactobacillus, and Carnobacterium belong to the normal microbiota of the gastrointestinal tract in healthy fish. However, it is well known that the population level of lactic acid bacteria associated with the digestive tract is affected by nutritional and environmental factors like dietary polyunsaturated fatty acids, chromic oxide, stress and salinity. Pathogenic lactic acid bacteria such as Streptococcus, Enterococcus, Lactobacillus, Carnobacterium and Lactococcus have been detected from ascites, kidney, liver, heart and spleen. Some antibiotic treatments and vaccinations have been proposed to cure or prevent these diseases that seem, however, to spread with the development of fish culture. It has also been reported that some lactic acid bacteria isolated from the gastrointestinal tract of fish can act as probiotics. These candidates are able to colonise the gut, and act antagonistic against Gram-negative fish pathogens. These harmless bacteriocin-producing strains may reduce the need to use antibiotics in future aquaculture.

Two experiments were conducted in order to compare the effects of several phospholipid (PL) sources prepared from soybean lecithin on growth and survival of start-feeding carp larvae. Eight diets were tested in each experiment. All diets contained 94% of the same casein–dextrin mixture and 6% of added lipid, consisting of peanut oil alone or supplemented with a PL source. In both experiments, diets supplemented with fractions enriched in phosphatidylinositol (PI) resulted in the highest survival (95% after 25 and 31 days, respectively). Addition of phosphatidylcholine (PC) allowed high initial growth rates during the first week of feeding, similar to or higher than those obtained with PI, but induced a peak of mortality afterwards and, in the first experiment, a high frequency of deformed fish. Larvae fed PC-enriched diets started to die at a larger size than larvae fed PL-deficient diets. Other tested fractions with phosphatidylethanolamine, phosphatidylserine or phosphatidic acid as the major PL class resulted in intermediate results between those given by PI- and PC-rich fractions. Dietary hydrogenated soybean PC resulted in a decreased growth compared to native soybean PC. Soybean lysolecithin was inferior to original lecithin for final larval growth and survival, but was superior to peanut oil without PL. Present results confirm that both the polar head group and the fatty acid composition of the dietary PL may affect their nutritional value for larval carp and suggest distinct requirements for PI and PC.

Atlantic salmon ( Salmo salar ), sea trout ( S. trutta m. trutta ) and brown trout ( S. trutta m. lacustris ) at four fish farms in northern Finland were examined in 1988–1992 for external lesions with filamentous bacteria. Phenotypic tests demonstrated that most of these bacteria were very similar to Flavobacterium johnsoniae . In two cases Flavobacterium columnare was isolated also. A total of 247 tanks (cases) with fish having external lesions containing filamentous bacteria were found, 57.5% of which contained only filamentous bacteria, while the rest had simultaneous non-filamentous bacterial or parasitic infection. In 31.6% of the cases more than 5% of the fish died in the course of the disease, but in 39.7% of the cases no mortality occurred or it was below 1%. The disease symptoms occurred on either the gills, jaws, skin, fins or tail, or on different combinations of these. Logistic regression analysis was used to assess the significance of the site of the symptoms, fish species, fish age, rearing density, other simultaneous infections, water temperature and the farm for fish mortality in the cases with filamentous bacteria. The results indicated that water temperature, fish species, gill or jaw erosion and the farm itself had the greatest effects on mortality.

Microbiota was studied in 20-day old seabass larvae after 10 days of feeding compound diets, in comparison with a control group kept live food. This early weaning caused bacterial overload in the larvae fed the normal compound diet (109 CFU per g of body weight). The bacterial load was significantly limited with a diet lacking ferrous salt in the mineral premix (3 × 108 CFU g−1). A similar range of associated flora was observed before weaning at day 10, but only 107 CFU g−1 were counted in the larvae fed Artemia till day 20. The bacterial surge in weaned larvae was due to one strain of Vibrio, especially dominant in the iron-supplemented diet. In spite of its opportunism, the strain did not seem pathogenic to starving seabass larvae challenged from day 5 to day 10. This Vibrio produced siderophore, protease, phospholipase and amylase. These extracellular products were also produced by 25 to 60% of the diversified flora of the Artemia-fed larvae. Lipase was the main extracellular product observed in the latter flora (80% of the isolates), whereas it was seldom produced in the weaned groups (less than 10%). The omission of dietary ferrous salt had no detrimental effect on survival and growth rates of the larvae, but limited bacterial load. It is concluded that diet formulation should take into account the effects on microbiota, based on this first example with iron limitation.

A beneficial effect of dietary phospholipid (PL) supplementation in purified diets in terms of survival, growth, resistance to stress tests, and occurrence of deformities has been demonstrated in larval and juvenile stages of various species of fish and crustaceans. The exact determination of PL requirements in larvae is complicated due to the difficulty to bio-encapsulate PL in live prey. Furthermore, the great variety in purity and composition of the PL sources, and the experimental conditions (such as diet formulation and extent of co/prefeeding with live food) makes it difficult to compare requirements determined with artificial diets. Larval stages are extremely sensitive to a dietary PL deficiency and require higher levels of dietary PL than juveniles. For most of the fish and crustacean species examined, the estimated PL requirement of larvae are in the range of 1–3% phosphatidylcholine + phosphatidylinositol (PC + PI) of diet dry weight. The absence of a PL requirement in the freshwater prawn Macrobrachium rosenbergii exemplifies the important species differences. The few studies evaluating single PL demonstrate that PC and PI are the most efficient in most species. The presence of an unsaturated fatty acid in sn−2 position of the PL molecule seems to be essential for the functionality of PL. Some studies in crustaceans reported a relation between PL requirements and the protein source in the diet. Various hypotheses have been formulated to explain the effect of PL. The PL effect is not related to the provision of choline, inositol or essential fatty acids (EFA). However, PL may be superior to neutral lipids for larvae as a source of EFA and energy due to their better digestibility. PL may improve the performance of the diet by improving the water stability of food particles, or by their action as antioxidant or feed attractant. The effect of dietary PL appears not to be explained by their emulsifying ability. However, there are proofs that dietary PL interfere with lipid transport, especially cholesterol transport in crustaceans, and with retention of fatty acids provided by dietary triacylglycerol. Although the origin of the requirement is still unclear, dietary PL supplementation has potential importance for the formulation of practical larval diets.

During the period 1977–1992 virological tests were conducted on a total of 2092 pools of elvers and eels ( Anguilla anguilla ), collected on 306 sampling occasions, in Denmark, United Kingdom, France and Sweden. From the 2092 pools, 91 virus isolates were obtained, of which 44 were of eel rhabdovirus (EVEX/EVA) belonging to the vesiculo group, 3 were of eel rhabdovirus of the lyssa group, 38 were of infectious pancreatic necrosis (IPN) virus, and 5 were herpes-like viruses. On one occasion only, a virus was isolated which was serologically related to viral haemorrhagic septicaemia (VHS) virus. On no occasion was infectious haematopoietic necrosis (IHN) virus isolated. An examination of available data on the occurrence and spread of VHS in Europe gave no evidence to indicate that A. anguilla might be a vector of this disease. This is supported by published data showing that elvers of A. anguilla appear to be refractory to experimental challenge with VHSV. It is concluded that, provided simple precautions are taken for elvers which might, by chance, be surface-contaminated with the virus, there appears to be little risk of spread of VHSV into previously VHS-free areas through international transfer of wild elvers for aquaculture purposes.