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The influence of energy content of glass eels (Anguilla anguilla) on their migratory behavior was investigated in November 2004 and February 2005 under laboratory conditions. Fish were sorted according to their response to a decrease in light intensity: Glass eels becoming active at dusk and using water flow to move with the current were considered as "active", whereas those remaining in the substratum throughout the catching period (24 h) were categorized as "inactive". "Active" glass eels exhibited higher energy content than "inactive" ones, whatever the catching month, and were more pigmented. Differences in percentage dry weight between "active" and "inactive" fish were already significant in the first pigmentary stages, suggesting that energy content plays a causal role in the estuarine migration of glass eels. The possible impact of energy state on the development of different migratory tactics in glass eels is discussed.

A blue variant of the rainbow trout, which appeared in a French fish farm, displayed an iridescent body color that was cobalt blue on the back, lighter on the undersides, and silvery on the belly and which held up to adult stage. This color was supposed to result from a Tyndall effect involving a structural arrangement of melanin pigments because it disappeared when it was associated with a depigmenting gene. This blue variant appeared to be governed by an autosomal recessive gene. Blue fry survival and body weight were about 25% less than those of wild-type sibs, but no major problem was observed in further breeding performances, including reproduction. These features do not correspond with those of the blue variants previously described in the rainbow trout.

Isotope turnover in muscle of ectotherms depends primarily on growth rather than on metabolic replacement. Ectotherms, such as fish, have a discontinuous pattern of growth over the year, so the isotopic signature of muscle (delta13C and delta15N) may only reflect food consumed during periods of growth. In contrast, the liver is a regulatory tissue, with a continuous protein turnover. Therefore, the isotopic composition of liver should respond year round to changes in the isotopic signature of food sources. Therefore, we predicted that (1) Whitefish in Lake Geneva would have larger seasonal variation in the isotopic variation of the liver compared to that of the muscle tissue, and (2) the isotope composition of fish muscle would reflect a long-term image of the isotope composition of the food consumed only throughout the growth period. To test these expectations, we compared the isotope compositions of Whitefish muscle, liver and food in a 20-month study. We found that the seasonal amplitude of isotope variation was two to three times higher in liver compared to muscle tissue. During the autumn and winter, when growth was limited, only the isotopic signature of liver responded to changes in the isotope composition of the food sources. The delta13C and delta15N of muscle tissue only reflected the food consumed during the spring and summer growth period.

Most regions in the tropics undergo high seasonal precipitation that produces cyclic patterns of riverine discharge, resulting in periods characterized by low and high water levels. Many chemical and bio-logical factors are affected by this hydrologic seasonality, and it therefore appeared to be very likely that aquatic food webs would also differ during the low and high water periods. Available carbon sources for fish are thought to be less varied during low water periods, but flooding during high water periods could bring fish into contact with a greater abundance and diversity of food sources such as terrestrial plants or the biofilms that grow on submerged terrestrial plants. At low water levels, higher fish densities may lead to more piscivory and less omnivory when compared with the high water periods. Therefore, trophic links within the fish communities may then be modified by water level changes in tropical reservoirs. To address this prediction, we performed stable isotope analyses of the most common species in Sélingué and Manantali, two large reservoirs in Mali (West Africa). Allochthonous and littoral carbon sources were shown to support fish production to a significant extent, even during low water periods. However, the allochthonous or littoral carbon contributions that sustained the top-predators production were indeed greater during the high water periods as expected. The expected higher omnivory in the high water period might have shortened the food chain when compared with the low water period. Some carnivorous fish species were shown to feed at lower trophic levels during high water periods in both reservoirs, but this was not a general pattern. Flooding did not, therefore, necessarily result in a shorter food chain when water levels were high.

Cyanobacteria including genus Oscillatoria are known to release toxins into waterbodies. To study the occurrence of toxic blooms in Lake Nantua, the Planktothrix rubescens species (Oscillatoria rubescens) was considered. At the same time, some physicochemical parameters were analysed to estimate their impact on toxin production. The investigations were conducted during summertime and the highest toxin concentration analysed by HPLC was detected in August (10.8 microg/l of lake water). The results of this work suggested that the toxin production increased when the light intensity, temperature, alkaline pH and phosphorus contents were at low levels. Moreover, the toxin production was positively related with NT/PT ratio. TLC analysis of the purified fractions revealed the occurrence of 4-7 polypeptide or protein bands. Two of them were shown to be toxic using Artemia bioassays and the most toxic one was identified as MCYST-RR.

A study was undertaken to investigate the environmental impact of herbicides on natural communities of freshwater periphyton and phytoplankton in the river Ozanne and in related nearby water reservoirs, including both pristine and pesticide- (atrazine and isoproturon) contaminated stations. The microalgal toxicity of both herbicides was investigated by short-term studies, using the in vivo fluorescence pattern to perform dose-effect experiments. The taxonomic composition of the communities sampled was assessed by microscopy and by HPLC pigment analysis. The EC50 (periphyton) or EC125 (phytoplankton) values, calculated using in vivo fluorescence endpoints, increased with the herbicide concentration found in the water. In contrast, the structure of the algal communities (periphyton) inhabiting the contaminated stations seemed to be permanently affected when compared to the reference community. A 'memory effect' could be detected, both in herbicide sensitivity and in the structure of periphytic communities that persisted even when peak contaminations had disappeared. This study shows that the response of algal communities is likely to reflect past selection pressures, and suggests that the function and structure of a community could both be modified by the persistent or repeated presence of microcontaminants in natural environments. We could use short-term ecotoxicological tests on freshwater microalgae to assess the effects of past temporary contaminations by agricultural pesticides, and combining this with diversity indices could make it possible to assess the ecotoxicological risk of herbicide contamination even when a complete chemical analysis of the contamination is not feasible.

The antifouling herbicide Irgarol 1051 has been detected in recent years in numerous estuaries, marinas, harbors and coastal areas, and in some harbors on Lake Geneva, but so far only a few studies have investigated the ecotoxicological effects of this compound on microalgae. The purpose of this study was to assess the ecotoxicological impact of Irgarol 1051 on the algal communities of Lake Geneva, and to compare its phytotoxicity to that of the common triazine herbicide, atrazine. We investigated the response of phytoplanktonic and periphytonic algal communities and single-species isolates collected from the lake, to the PS II inhibitor Irgarol 1051 (growth, proxy of photosynthetic activity and community structure). A short-term bioassay was developed based on in vivo fluorescence, together with nanocosm experiments with natural algal communities, and single-species tests on algal strains isolated from the lake. The toxicity of Irgarol 1051 towards periphyton and phytoplankton was shown to be higher than that of atrazine. Indications of the tolerance induced by this triazine in the algal communities of Lake Geneva, suggests that even at the levels of contamination reported in some parts of the lake, Irgarol 1051 is already exerting selection pressure. Information about sensitivities, selection and tolerance from laboratory experiments are used to explain the observations in natural microalgal communities from the lake.

Acetyl-CoA carboxylase (ACoAC) catalyses the carboxylation of acetyl-CoA into malonyl-CoA. This product plays a pivotal role in the regulation of energy metabolism since it is both a substrate for fatty acid synthesis and an inhibitor of the oxidative pathway. The present study was initiated to analyse the modulation of ACoAC activity in liver and selected extrahepatic tissues of rainbow trout (Oncorhynchus mykiss) by dietary changes as a contribution to the understanding of the nutritional control of lipid metabolism in fish. Short-term effects of food intake were studied by measuring ACoAC activity in the liver and dorsal white muscle at different time intervals after a meal. Only slight variations were observed in the muscle during the period 2-72 h after the meal. The long-term effects of an increase in dietary lipids or carbohydrates levels were examined by measuring ACoAC activity in the liver, adipose tissue, intestine, kidney, red muscle, dorsal and ventral white muscles of trout after 3 months of feeding with different diets. ACoAC activity is stimulated by a high-digestible starch diet in the abdominal adipose tissue and the white muscle. A high-lipid diet decreases ACoAC activity in the liver and the intestine, but not in other tissues. Contrary to mammals, a rapid adaptation of ACoAC activity to food supply is not effective in rainbow trout. However, a long-term nutritional control of ACoAC activity does occur in this species, but the target tissue differs with the predominant non-protein energy sources in the diet. The present results suggest the potential existence of two ACoAC isoforms with different tissue distribution as has been observed in mammals and birds.

Two rapeseed meals (RM1 and RM2), containing glucosinolates at a concentration of 26 and 40 micromol/g, respectively, were incorporated at increasing levels (10, 20, and 30% for RM1 and 30 and 50% for RM2) in diets of juvenile rainbow trout. Disturbances in the thyroid axis appeared after 14 days of feeding (with a dietary incorporation level of 10%). The dietary supplementation with T(3) or iodine induced an increase in plasma T(3) levels, compared to that in fish fed the RM diets, and reduced the deleterious effect of RM on growth. When trout were reared in seawater, there was also a slight increase in thyroid hormone levels. TSH treatment had no effect on the thyroid hormone plasma levels. The incorporation of 30% of RM1, which induced a lower dietary content of toxic compounds than RM2, led to a rapid decrease of plasma T(4) and T(3) levels, but growth was affected only after 6 months of feeding. During these studies, the deiodinase activities responded in a complex manner to restore plasma and tissue levels of T(3).

Molecular techniques are of growing importance in the study of anthelmintic resistance in trichostrongylid worm populations. A knowledge of the genetic determinants of benzimidazole (BZ) resistance has made it possible to construct a molecular tool for genotyping individual worms, in respect of mutation of the beta-tubulin gene responsible for BZ resistance. This tool offers new possibilities in the diagnosis of BZ resistance, and also in the study of anthelmintic use and other breeding management factors that can affect the selection of BZ-resistant alleles in worm populations. New molecular methods have also made it possible to study the origin and diversity of BZ-resistant alleles in trichostrongylid populations. The results demonstrate the value of a multidisciplinary approach to the study of anthelmintic resistance, combining molecular, ecological and epidemiological techniques.

The effect of light-dark (LD) cycle and food availability was tested on the demand-feeding rhythm of single and groups of rainbow trout and European catfish. Under LD and free food access, most trout and catfish displayed, respectively, a diurnal and a nocturnal pattern of demand-feeding activity, whereas a few fish or groups of fish switched from diurnalism to nocturnalism or vice versa. In both species held under constant lighting conditions and a restricted feeding (RF) cycle (RF 20:4), the demand-feeding rhythm rapidly synchronised to food availability. The demand-feeding rhythm was under endogenous control and, in rainbow trout, periodogram analysis suggested the existence of two oscillators, one synchronised by photoperiod (LEO) and the other by food (FEO). When submitted to both LD and RF cycles, LD was, at least in the rainbow trout, the dominant zeitgeber synchronising the demand-feeding rhythm. In catfish, food availability rapidly synchronised demand-feeding rhythm. Finally, in both species, the synchronisation of single fish to LD or feed availability appeared slower than that of groups of fish, supporting the idea that social organisation affects the circadian activity in fish.

Growth modifications caused by various concentrations of atrazine and nicosulfuron were monitored in closed and continuous culture of Chlorella vulgaris (chlorophyta), Navicula accommoda (diatomophyta), and Oscillatoria limnetica (cyanophyta). The concentration at which algal growth rate was reduced twofold (EC50) was determined in the three species for both herbicides. Comparatively, the two toxicants were applied at 10 microg/l level in microcosms inoculated with natural phytoplankton from Lake Geneva. The relative abundances of major phytoplanktonic species were measured by algal cell count at the beginning and at the end of each experiment. Atrazine and nicosulfuron have different targets in plant metabolism, respectively, photosystem II (PSII) and acetolactate synthase (ALS), and the expected effects were different. Generally, the cultured phytoplankton exhibited various sensitivities, depending on species or herbicide. In the microcosms, the major taxa of natural phytoplanktonic samples exhibited various patterns, from acute toxicity to growth enhancement. For example, the diatoms inside the community were not affected by atrazine and nicosulfuron, except for Stephanodiscus minutulus that was sensitive to both, and Asterionella/formosa that was sensitive only to nicosulfuron. The specific physiology and the relationships among the phytoplanktonic communities have to be carefully considered when one would try to predict the extent of herbicide action on natural phytoplankton using in vitro tests. There is a need to test the toxic effect on various cultured strains, representative of most of the taxonomic composition of natural communities, to take into account the wide range of sensitivities and reaction to herbicide contamination. But this is not enough to give a solid frame when transposing the results to the field, and the use of more ecologically relevant systems is recommended.

A study was conducted on common carp (Cyprinus carpio L.) to determine the effects of environmental temperature experienced by embryos and larvae on the development of myotomal white muscle. Eggs from one female were divided into two groups following fertilisation and incubated at constant pre-hatch temperatures of 18 or 28 degrees C. At hatching, larvae from the 18 degrees C-incubated eggs were divided into two groups and either reared at the same temperature of 18 degrees C ('cold' group) or transferred over a period of 5 days (at 2 degrees C per day) to 28 degrees C ('transferred' group). Larvae hatched from eggs incubated at 28 degrees C were reared at the same temperature of 28 degrees C ('warm' group). Larvae were sampled at two developmental stages (stage 1, inflation of the back chamber of the swimbladder; stage 2, inflation of the front chamber of the swimbladder) and at 26 days post-hatching. The maturation of myotome shape during larval life was studied in parallel with the changes occurring in the organisation of white fibres. At stage 1, the epaxial part of the myotomes surrounding the vent had the shape of lamellae inclined backwards, and only one central layer of white fibres was present. At stage 2, the epaxial part of the myotomes began to acquire a V-shape, which was well developed at 26 days post-hatch. At stage 2 and at 26 days post-hatch, two layers of white fibres were identified: the initial central layer and a second apical layer. These differ in their orientation, the initial central layer being orientated backwards and the apical layer forwards, and in the mean fibre diameter, which is greater in the initial central layer. Studies on the effects of temperature (constant 18 degrees C, constant 28 degrees C, transfer from 18 to 28 degrees C at hatching) were carried out according to both the developmental stage and the length of the larvae. At stage 1, no significant differences were found between the three groups for larval standard length and muscle variables. The number of fibres in one quadrant of epaxial white muscle sectioned at the level of the vent was 100-111. At stage 2, there were significant differences between groups. Larval standard length and mass were higher in the cold group than in the warm group. The transferred larvae were of intermediate standard length but had a significantly higher cross-sectional area of white muscle than either of the other two groups. This increase in surface area was related to a 50 % greater fibre number (233) in the transferred larvae compared with the cold (165) or the warm (152) larvae. The increase in fibre number was more marked for large-diameter ( >20 microm) white fibres located in the initial central fibre layer (+58-72 % in transferred larvae) than in small-diameter ((less than equal to) 10 microm) white fibres mainly located in the apical layer (+18-35 %). In 26 days post-hatch samples, transferred larvae still showed a higher total number of white fibres than warm larvae, but the difference was no longer significant when the total number of white fibres was regressed against larval standard length, suggesting that this stimulation may be temporary.

In fish, dietary digestible energy (DE) content is a major factor controlling feed intake. It was therefore of interest to determine how circadian rhythm of feeding activity is influenced by the dietary DE levels. To that end, groups of European sea bass were fed on demand by means of self feeders, under light-dark and constant light conditions, with a fixed or an unlimited amount of feed with variable lipid contents. Daily total feed intake, but not the feeding rhythm, was adjusted in relation to the DE content of the diet regardless of the lighting conditions. We conclude that a satiation mechanism was likely responsible for the regulation of feed intake in relation to the dietary fat content but was not acting in itself on the mechanisms that drive the free-running rhythms of feeding activity. These results are giving additional evidence that a true endogenous clock is driving feeding activity rhythms in fish.

Our main objective was to verify whether the dietary ascorbic acid (AA) requirement of juvenile European sea bass (Dicentrarchus labrax) varies as a function of different physiological needs. Practical diets with eight (0, 5, 10, 20, 40, 80, 160, 320 mg AA/kg diet) levels of ascorbic acid polyphosphate were fed to sea bass (mean weight: 0.7 g) for 15 wk. At the beginning and at the end of the feeding trial, tissues were sampled for vitamin C and hydroxyproline (HyPro) analysis. Dose-dependent responses of skin and whole body HyPro concentrations and hepatic AA concentration to dietary vitamin C levels were observed. Skin and whole body HyPro concentrations were low in sea bass fed AA-deficient diet, 217 and 15 nmol/g tissue, respectively. HyPro levels increased with increasing dietary levels, reaching plateaus of 297 and 45 nmol/g tissue in the skin and whole body at dietary vitamin C levels of at least 5 and 31 mg AA/kg. Hepatic AA level increased with increasing dietary levels, reaching a plateau of 474 pmol/g tissue in juveniles fed at least 121 mg of AA/kg. We concluded that hepatic AA saturation is the most stringent response criterion for determination of the vitamin C requirement in juvenile European sea bass.

The responses of algae to herbicides depend on the sensitivity of each species, but competition within algal communities may be an important regulator of the effects of herbicides on aquatic systems. The impact of herbicides on algae also depends on abiotic factors like nutrients, light, and temperature. We examined the tolerance of the alga Oscillatoria limnetica Lemmermann to the photosystem II inhibitor herbicide atrazine under different culture conditions to assess those interactions between herbicides and biotic and abiotic factors. The density of the cyanobacterium O. limnetica was determined in natural phytoplanktonic assemblages and in unialgal cultures in medium containing 10 microg/L atrazine. Experiments (total of 13) were conducted in spring and early and late summer, during which the effect of atrazine varied in nature and intensity. The growth of the cyanobacterium was always inhibited in cold experiments, whereas it was stimulated in warm experiments within the natural phytoplankton assemblage, but unaffected in pure culture. Laboratory experiments with unialgal culture showed that the sensitivity to atrazine increased as the temperature decreased. Phytoplankton community structure, interactions between species, and environmental parameters (e.g., temperature) are important factors controlling the responses of cyanobacteria to the herbicide. These interactions between sensitivity to herbicides and environmental factors may reduce or emphasize the effects of pollution in aquatic systems. Thus, the ecotoxicological relevance of herbicides in aquatic systems is quite complex and cannot be assessed by single-species short-term laboratory toxicological tests.http://link. springer-ny.com/link/service/journals/00244/bibs/37n4p472.++ +html

We studied 12 size-matched pairs of Atlantic salmon, Salmo salar, in an experimental stream in southwest France, to determine whether fish activity and motivation changed during the course of reproduction. The absolute weight of spawners did not affect their spawning activity. On average, females deposited their eggs within 3 days in nine nests. Male and female breeding behaviours changed throughout the reproductive period. This cyclic variation in behaviour appeared to be determined in part by the activity of the other sex, as a consequence of complex interplay between the sexes, but also largely by the stage of the spawning period. During the first three ovipositions, male-female stimulus-reaction chaining became more consistent just before spawning, which may help synchronize gamete release for successful fertilization. During the last three ovipositions, sequence chaining between the sexes was less coherent, possibly as a result of reduced mate attractiveness and/or physiological limitations. Copyright 1999 The Association for the Study of Animal Behaviour.

The major source of aquatic animal production is based on fisheries. Currently, a significant portion of the fishery resources is used for non-food purposes. One of the first steps towards rational exploitation of the natural fishery resources should be to limit such abuse and address the needs of an increasing global population. The challenge for the fishery industry is to develop methods for early and reliable prediction of stock availability and fluctuations in order to maintain a sustainable supply. With the continuing decline in fishery resources, aquaculture is slowly becoming an interesting alternative for the supply of animal protein of high nutritional value. Aquaculture, like any other human activity can have adverse effects on the environment. In this context, the semi-intensive farming systems prevailing in the tropical areas should be encouraged, substantiating them with scientific knowledge on the nutrient flow in such confined ecosystems. In some instances of intensive culture systems, progress has been made in aquaculture waste management by applying adequate nutritional strategies. Such an approach should be extended to other cultured species. Be it production for profit or production for food, sustainable aquatic animal production is intimately connected with all human activities, in as much as all these activities invariably have an effect on water quality. Hence, greater consideration is needed towards a general strategy of protecting the aquatic ecosystem at all levels.

A study was conducted to evaluate tissue storage and mobilisation of L-ascorbic acid (AA) in the Siberian sturgeon (Acipenser baeri) fed three different experimental diets. The three treatments consisted of a diet devoid of vitamin C (diet A0) and two diets supplemented with equivalent of 300 mg AA kg(-1) in the form of either silicone-coated ascorbic acid (diet SC) or of ascorbyl-2-polyphosphate (diet AP). During the first phase (4 months) of the trial, six batches of 130 Siberian sturgeon (initial body weight: 25.5±0.5 g) each were fed one of the three diets in duplicate. During the second phase (3 months), fish from groups SC and AP were switched to diet A0 and those fed diet A0 during the first phase were switched to diet SC. Irrespective of the dietary treatment, growth rates were not significantly different from each other. At the end of phase I, in all tissues studied, total ascorbic acid (TAA) concentrations were higher in Siberian sturgeon fed diet AP than in the other two groups. During phase II, tissue ascorbate depletion was also higher in the AP group than in the other two groups. Transfer of the AA-free diet fed group onto a diet supplemented with 300 mg AA kg(-1) (diet SC) led to a slight increase in the TAA concentrations in all tissues. Blood plasma tyrosine concentrations were not significantly different between the three groups. Whole-body collagen levels were affected by dietary AA levels or forms at the end of phase I; the differences were not significant at the end of phase II. Muscle collagen levels were slightly affected. L-Gulonolactone oxidase activity was found in the kidney of Siberian sturgeon, but not in the liver. The ascorbyl-2-polyphosphate appears to be either better utilised by Siberian sturgeon, like in many other teleosts, or more stable than the silicone-coated AA during food processing and storage. Presence of L-gulonolactone oxidase activity in Siberian sturgeon kidney combined with the absence of gross scorbutic signs in AA-free diet fed groups expressing very good growth rates suggested no need of dietary AA byA. baeri.

When assessing pesticides toxicity on test organisms, the use of organic solvents is frequently required to formulate solutions of pesticides having low or moderate water solubility. These solvents may influence the results of toxicity tests. This study examined the effects of ethanol and dimethyl sulfoxide (DMSO) on two species of algae, Chlorella vulgaris and Selenastrum capricornutum. The interactives effects of these organic solvents with various concentrations of atrazine were tested to analyse how these solvents can affect the toxicity of atrazine. Toxicity was measured as the change in chlorophyll (a) content (estimated via fluorescence) in cultures of the test organism that were incubated over a 96-h period at standard conditions of temperature and light. In the absence of atrazine, ethanol was toxic to both algae, yielding significant inhibition of chlorophyll (a) content at concentrations as low as 0.05%. Morever, S. capricornutum was less sensitive to ethanol than was C. vulgaris. DMSO did not show any toxic effects on either chlorophycea. At concentrations up to 0.5%, DMSO interacted additively with atrazine for both chlorophycea. An additive response was also observed with ethanol towards S. capricornutum. For C. vulgaris, ethanol interacted antagonistically at most of atrazine concentrations and gave few additive and synergistic interactions. An additive response of an atrazine-solvent mixture indicate the inherent toxicity of the atrazine. Since DMSO generally gave additive responses for both algae, it can be considered as an adequate organic solvent to use in bioassays.

Trout reared at 8 or 18 degrees C were fed twice a day almost to satiation with 1 of 3 experimental diets. The diets were formulated to contain the same levels of protein (43%, dry matter (DM) basis) and digestible energy (around 15 kJ/g DM), but different carbohydrate/lipid ratios 30:7 to 23:14). Time-course studies of nitrogen excretion and glycaemia were also carried out. After 12 weeks of feeding, growth, protein retention and body composition were not influenced by the dietary treatment in trout reared at 8 degrees C. At 18 degrees C, the protein retention was not affected by dietary treatment, but the weight gain tended to be higher in trout fed the diet with the lowest carbohydrate/lipid ratio. This result was due to higher body lipid deposition in these trout. Nitrogen excretion was not influenced by dietary treatment, but was higher at 18 degrees C than at 8 degrees C because of a higher feed intake. Glycaemia increased with dietary level of digestible carbohydrate and the highest plasma glucose level was attained later at 8 degrees C in comparison to 18 degrees C.

The effect of the type of dietary starch (gelatinized vs native) on the biological value of fish meal (FP) and fish soluble protein concentrate (CPSP) was studied through the nitrogen balance in rainbow trout (Oncorhynchus mykiss) reared for 3 weeks at 2 water temperatures: 8 or 18 degrees C. The protein sources were included in diets at a level of 60% and gelatinized or raw starch at a level of 30%. Gelatinized starch improved the biological value of FP and CPSP by reducing the metabolic nitrogen losses. Trout fed the diet with CPSP had a higher nitrogen excretion than those fed the diet with FP. The biological value of both protein sources was unaffected by water temperature.

A method for the direct measurement of plasma amino acid flux, in rainbow trout, using the continuous infusion of L-[U-(14)C]-leucine with ALZET mini-osmotic pumps implanted into the peritoneal cavity, was developed. The fish were fed successively on three different diets (a commercial control diet, a semi-purified diet and a purified diet) during the 4 weeks of experiment. The amounts of radioactivity in the free pool and the protein of both the plasma and skin mucus were measured in these fish. The total flux of leucine was calculated either from the specific activity of leucine in the plasma (61.8 mg leucine. 100 g(-1).d(-1)) or from the amounts of labelled and unlabelled leucine flowing into the skin mucus protein (61.5 mg leucine. 100g(-1).day(-1)). The total plasma flux was not affected by changes in the diet. The contributions of total leucine oxidation and whole body protein turnover to plasma leucine flux (80% and 20% respectively) were estimated in fish fed the semi-purified diet.

In wild fish, gonad maturation and spawning induce modifications in feeding behaviour and dynamics of body stores which are possibly responsible for metabolic disorders. Conversely, food manipulations can modify reproduction of captive female broodstock. A restricted diet during early stages of the life cycle delays the first maturation age, a quantitatively restricted food supply during the stages of oocyte differentiation reduces the egg number, while a reduction of food levels during the last phases of oogenesis has only a small effect on egg size, composition and hatchability. During the spawning period, salmonid female broodstock seem to be more able to utilize carbohydrates than immature fish, they valorize the energy brought in by fats and have low quantitative requirements for proteins (28%). On the other hand, Red Sea bream broodstock have higher needs for proteins (45%).The incorporation into diet of liposoluble vitamins and essential fatty acids is necessary for normal reproduction, but (n-6) fatty acids seem to play a more important role than in juveniles. Although the effects and physiological role of carotenoids are not yet well known in salmonids, they are necessary for normal development in Red Sea bream. Although little work has been done on the effects of mineral nutrition, special attention must be paid to trace elements, manganese in particular.The major part of this review concerns female broodstock, since very little interest has been devoted to males.