References of "Mélard, Charles"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailEffects of geographic origin on growth and food intake in Eurasian perch (Perca fluviatilis L.) juveniles under intensive culture conditions
Mandiki, S. N. M.; Blanchard, G.; Mélard, Charles ULg et al

in Aquaculture (2004), 229(1-4), 117-128

Survival, growth, and food intake of Eurasian perch (Perca fluviatilis) juveniles from different stocks originating from various geographic regions of Europe were compared under the same conditions of ... [more ▼]

Survival, growth, and food intake of Eurasian perch (Perca fluviatilis) juveniles from different stocks originating from various geographic regions of Europe were compared under the same conditions of laboratory-scale intensive culture. In Experiment 1, four stocks originating from Italy (1), southwest (SF) and northwest (NF) France, and Belgium (B) were examined at larval and early juvenile (initial body weight, IBW = 0.53 g) stages. In Experiment 2, B stock was compared to a Finnish (F) one in two trials, including small (IBW = 1.26 g) and large (IBW = 32 g) juveniles. In Experiment 3, small (IBW = 1.29 g) and large (IBW = 7.33 g) juveniles from Polish (P), F, and B stocks were examined. In Experiment 1, body weight means at hatching and survival at the end of the larval stage were significantly lower in the I and SF stocks than in the B and NF stocks. In the early juvenile stage, survival and growth rates were significantly lower in the I and SF stocks than in the B and NF ones. In Experiment 2, {early juvenile stage} survival in the F stock was significantly lower than in the B stock, partly due to a higher incidence of cannibalism. During this stage, growth rates and food intake or feed efficiency in the F and B stocks were comparable, but at the end of the juvenile stage, the F stock outperformed the B one. In Experiment 3, survival in all the three stocks was comparable both in small and large juveniles. In contrast to the higher performance of F juveniles in Experiment 2, growth rates were comparable between the B and F stocks, and fish from the P stock had the highest growth rates. The results indicate a high level of variation within and between hatchery stocks in survival rates, growth rates, and food intake. These variations depended on the geographic origin of the fish, with the lowest survival and growth potentials being in the stocks originating from the southern regions. These findings highlight the interest in evaluating growth and food consumption of different Eurasian perch stocks. Such evaluation is a necessary tool for genetic selection in improving performance in perch aquaculture. (C) 2004 Elsevier Science B.V. All rights reserved. [less ▲]

Detailed reference viewed: 26 (1 ULg)
Full Text
Peer Reviewed
See detailSize heterogeneity, cannibalism and competition in cultured predatory fish larvae: biotic and abiotic influences
Kestemont, P.; Jourdan, S.; Houbart, M. et al

in Aquaculture (2003), 227(1-4), 333-356

Growth heterogeneity is a central problem in larviculture and especially in predatory species. It can be influenced by a wide range of intrinsic and environmental factors, of which the respective ... [more ▼]

Growth heterogeneity is a central problem in larviculture and especially in predatory species. It can be influenced by a wide range of intrinsic and environmental factors, of which the respective influences are largely unknown. The role of non-interactive (temperature, day length, light intensity, food availability and composition) and interactive factors (stocking density, initial size heterogeneity, hatching time) on growth, survival and size heterogeneity was measured in larvae and post-larvae of the European seabass Dicentrarchus labrax and Eurasian perch Perca fluviatilis. Embryos hatching later than others were found less competitive than those hatching earlier in both species, but to a greater extent in perch. By contrast, the final size heterogeneity in both species was independent from the initial size heterogeneity or recurrent size sorting. High stocking density had a positive effect on perch larvae, no effect on seabass larvae and a negative impact on the post-larvae of both species, owing principally to density-dependent access to food. Day length and light intensity produced contrasting results in larvae and post-larvae. Larvae of both species performed better under bright light and continuous day length. Post-larvae of seabass performed equally well at different light levels but did better under short day lengths, whereas post-larvae of perch were unaffected by day length but performed better under reduced light levels. Increasing food availability resulted in increasing performance of perch larvae, although cannibalism was higher for submaximal than for maintenance rations. The similarity between the two species at the larval stage, and differences at the post-larval stage can be accounted for by the increasing specialisation towards specific environments and niches. Regarding the impact of rearing factors on growth, survival and size heterogeneity, interactive variables impacted essentially on growth and survival, whereas size heterogeneity was chiefly influenced by non-interactive variables, either directly or indirectly via interactive mechanisms such as cannibalism and size-dependent mortality. (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

Detailed reference viewed: 53 (5 ULg)
Full Text
Peer Reviewed
See detailEffect of stocking density on the dynamics of cannibalism in sibling larvae of Perca fluviatilis under controlled conditions
Baras, E.; Kestemont, P.; Mélard, Charles ULg

in Aquaculture (2003), 219(1-4), 241-255

The effect of stocking density (10, 31.6 and 100 larvae 1(-1); three replicates per treatment) on the day-by-day dynamics of survival, growth and cannibalism was examined in sibling perch larvae reared ... [more ▼]

The effect of stocking density (10, 31.6 and 100 larvae 1(-1); three replicates per treatment) on the day-by-day dynamics of survival, growth and cannibalism was examined in sibling perch larvae reared from eyed-egg stage in 100-1 cages (16L:8D, 20.0 +/- 0.5 degreesC, O-2 greater than or equal to 6.0 mg 1(-1); feeding in excess with live Artemia nauplii during the photophase) during the first 3 weeks of exogenous feeding. Larvae unable to achieve the transition to exogenous feeding died in between 7 and I I days post-hatch. Later, mortality from causes other than cannibalism never exceeded 1% day(-1). Cannibalism did not start before days 10 - 11 and first consisted in the incomplete ingestion of prey attacked tail first, exclusively. This type of cannibalism never caused losses higher than 2.0% of the initial stock, and ceased after days 16-18. From days 12-14 onwards, differential growth was apparent, and cannibals turned to complete cannibalism of small prey ingested head first, which caused greater losses (28-53% of the stock). Increasing the stocking density did not compromise growth and decreased the overall impact of cannibalism through several complementary mechanisms: (i) a postponed emergence of cannibalism, (ii) a lower proportion of cannibals in the population, and (iii) probably a lower rate of cannibalism per capita as predation was complicated and less directed at high stocking density. (C) 2003 Elsevier Science B.V. All rights reserved. [less ▲]

Detailed reference viewed: 32 (3 ULg)
Full Text
Peer Reviewed
See detailInheritance of sex in two ZZ pseudofemale lines of tilapia Oreochromis aureus
Desprez, D.; Mélard, Charles ULg; Hoareau, M. C. et al

in Aquaculture (2003), 218(1-4), 131-140

This paper reports a study on the sex determination system of the blue tilapia, Oreochromis aureus. Investigations were carried out using a pseudofemale line in two populations of O. aureus, known as ... [more ▼]

This paper reports a study on the sex determination system of the blue tilapia, Oreochromis aureus. Investigations were carried out using a pseudofemale line in two populations of O. aureus, known as Egyptian Population (EP) and Israel Population (IP). In O. aureus, males are the homogametic sex (ZZ/ZW), and sex reversal of fry with estradiol results in the production of some functional sex-reversed fish with a female phenotype and ZZ male genotype, known as pseudofemales or A-females. Crosses between ZZ pseudofemales and ZZ males theoretically should provide monosex ZZ male progeny only. We have studied the sex ratios of progeny from 43 IP (F-2 to F-3 generations) and 51 EP (F-1 to F-5 generations), pair-matings between normal males and pseudofemales. In IP, the male percentage in progenies ranged between 83% to 100% in F-2 and 66% to 100% in F-3. In EP, male percentage was more constant, varying from 88% to 100% in F-1, from 96% to 100% in F-3 and from 97% to 100% in F-5. In EP, F-2 and F-4 pseudofemales produced only monosex male progeny. This apparent difference in sex ratio frequency distributions between the two O. aureus pseudofemale lines could be due to the selection of males. EP pseudofemales were mated with their siblings for F-2 and F-3 pseudofemales or with closely related males for F-4 and F-5 pseudofemales. Conversely, IP pseudofemales were crossed with nonrelated males originating from research center broodstock, resulting in a higher proportion of females in sex ratio of progenies from successive generations of pseudofemales. The role of inbreeding is discussed in the context of predominantly monofactorial sex chromosome determination system operating in this species, influenced by other factors (genetic and environmental). The present study also shows that it is possible to fix the male sex determining factors (Z sex chromosome and genetic factors) in a line of pseudofemales, producing a high percentage of male progeny in five successive generations. (C) 2003 Elsevier Science B.V. All rights reserved. [less ▲]

Detailed reference viewed: 108 (1 ULg)
Full Text
Peer Reviewed
See detailProduction of a high percentage of male offspring with a natural androgen, 11 beta-hydroxyandrostenedione (11 beta OHA4), in Florida red tilapia
Desprez, D.; Geraz, E.; Hoarea, M. C. et al

in Aquaculture (2003), 216(1-4), 55-65

This paper reports the effects of a natural androgen, 11beta-hydroxyandrostenedione (11betaOHA4), on sex-reversed fry of the Florida red tilapia. In a first approach, the optimal dosage and duration were ... [more ▼]

This paper reports the effects of a natural androgen, 11beta-hydroxyandrostenedione (11betaOHA4), on sex-reversed fry of the Florida red tilapia. In a first approach, the optimal dosage and duration were determined in the laboratory. The sex-reversal treatment was applied on post-yolksac stage fry (10 days after fertilisation at 27degreesC. Dosages of 20, 30, 40 and 50 mg of 11betaOHA4 kg(-1) of food were used during periods ranging from 10 to 35 days. Dosages of 40 or 50 mg of 11betaOHA4 kg(-1) of food during 21-35 days significantly increased the male percentage in sex-reversed groups in comparison to control groups. A lower but still significant deviation of the male percentage was observed when a dosage of 40 mg kg-1 was given during at least 28 days. Lower dosages did not significantly affect the sex ratio of treated groups. Based on the results of these observations, a follow-up study was conducted to evaluate the efficiency of this natural androgen for an intensive production of sex-reversed fry. Optimal dosage (50 mg kg-1) and treatment duration (28 days) were applied to increasing stocking density of fry (8000-11,000 fish m(-2)), producing a mean male percentage of 99.1% on the 510,000 treated fry. This study demonstrates the masculinizing efficiency of 11betaOHA4 in Florida red tilapia. Interest of a natural androgen, used in sex-reversal treatment, is discussed, particularly for the Florida red tilapia strain. (C) 2003 Elsevier Science B.V. All rights reserved. [less ▲]

Detailed reference viewed: 20 (1 ULg)
Full Text
Peer Reviewed
See detailInduce triploidy by heat shock in Eurasian perch, Perca fluviatilis
Rougeot, Carole ULg; Minet, Laurent; Prignon, Christian ULg et al

in Aquatic Living Resources (2003), 16(2, MAR-APR), 90-94

In Eurasian perch (Perca fluviatilis), females grow significantly faster than males. Moreover, gonadal development has a significant negative impact on somatic growth and fillet yield. In order to induce ... [more ▼]

In Eurasian perch (Perca fluviatilis), females grow significantly faster than males. Moreover, gonadal development has a significant negative impact on somatic growth and fillet yield. In order to induce sterility, triploidy induction was attempted by subjecting fertilised eggs to heat shocks. Different combinations of temperature (28, 30, 34, 35 and 36 degreesC), duration (2, 5, 10 and 25 min) and time of shock initiation (TI = 3, 5 and 7 min post-fertilisation) were tested. Flow cytometry analysis was used to assess ploidy level of control and heat-shocked larvae. Low intensity (28-30 degreesC) and long duration (10 and 25 min) shocks lead to significantly higher survival (44 +/- 26%) and triploidisation (71 +/- 26%) rates than high intensity (34-36 degreesC) and short duration (2 and 5 min) shocks (17 +/- 19% and 21 +/- 26%, respectively). The most effective conditions for efficient triploidy induction were low intensity shock of 30 degreesC, applied 5 min post-fertilisation for 25 min. This treatment led to the production of all-triploid populations (100%) with up to 43% survival rate. (C) 2003 Editions scientifiques et medicales Elsevier SAS and Ifremer/IRD/Inra/Cemagref. All rights reserved. [less ▲]

Detailed reference viewed: 64 (8 ULg)
Full Text
Peer Reviewed
See detailOntogenetic variations of thermal optimum for growth, and its implication on thermolabile sex determination in blue tilapia
Baras, E.; Mpo'n'tcha, A.; Driouch, H. et al

in Journal of Fish Biology (2002), 61(3), 645-660

Knowledge of how the optimum temperature for growth (Tdegrees(opt)) varies during ontogeny, and how close it is to the temperatures that induce Phenotypic masculinization is fundamental to the ... [more ▼]

Knowledge of how the optimum temperature for growth (Tdegrees(opt)) varies during ontogeny, and how close it is to the temperatures that induce Phenotypic masculinization is fundamental to the understanding of the evolution of thermolabile sex determinism (TSD) in fishes. In blue tilapia Oreochromis aureus, Tdegrees(opt) is 32.6degrees C at the start of exogenous feeding (10 mg fish) and it decreases by c 1degrees C each time that the fish bode mass increases by an order of magnitude. Temperatures <35degrees C are not sufficient to induce complete phenotypic masculinization. Based on a multiple-regression model (r(2)=0.938) plotting growth against body mass and water temperature. genotypically female tilapia living at high temperatures during the thermosensitive period (21-28 days) and being reversed into phenotypic males should incur an initial growth disadvantage over fish living at Tdegrees(opt) but not over those living at slightly colder temperatures (27-29degrees C). This initial disadvantage would be later compensated for by faster growth because of between-sex growth dimorphism to the detriment of phenotypic females. These arguments suggest that there is no definite pressure against the selection of TSD in blue tilapia and probable other Oreochromis spp. (C) 2002 The Fisheries Society of the British Isles. Published by Elsevier Science Ltd. All rights reserved. [less ▲]

Detailed reference viewed: 29 (6 ULg)
Full Text
Peer Reviewed
See detailInfluence of sexual genotype on the behaviour of females (genotype WZ) and pseudofemales (genotype ZZ) in the tilapia Oreochromis aureus
Ovidio, Michaël ULg; Desprez, Damien; Mélard, Charles ULg et al

in Aquatic Living Resources (2002), 15(3), 163-167

17alpha-ethynylestradiol sex-reversed males of Oreochromis aureus (pseudofemales, DeltaF, genotype ZZ) are used in aquaculture to produce a male monosex population by crossing with ZZ homogametic normal ... [more ▼]

17alpha-ethynylestradiol sex-reversed males of Oreochromis aureus (pseudofemales, DeltaF, genotype ZZ) are used in aquaculture to produce a male monosex population by crossing with ZZ homogametic normal males. When placed with males (M) and females (F) in the same spawning tank, the spawning rate of F is higher than for DeltaF. In order to understand this phenomenon, comparisons were made between the behaviour of 18 F (446 +/- 96 mm) and 18 DeltaF (401 +/- 59 mm). DeltaF showed a more aggressive behaviour and were significantly more dominant than normal F in fighting pair experiments (F x DeltaF) or in fighting group experiments in four different stocking densities (8, 12, 16 and 83 fish 10(-3) l with F/DeltaF ratio = 1). DeltaF were also more aggressive towards males than F were. The results support the idea that behavioural differences exist between F and DeltaF These differences are probably due to the effect of the sexual genotype on behaviour. (C) 2002 Ifremer/CNRS/Inra/IRD/Cemagref/Editions scientifiques et medicales Elsevier SAS. All rights reserved. [less ▲]

Detailed reference viewed: 41 (8 ULg)
Full Text
Peer Reviewed
See detailSex control and sex determinism study in Eurasian perch, Perca fluviatilis, by use of hormonally sex-reversed male breeders
Rougeot, Carole ULg; Jacobs, Bruno; Kestemont, Patrick et al

in Aquaculture (2002), 121

Detailed reference viewed: 80 (25 ULg)
See detailSex control in Eurasian perch, Perca fluviatilis
Rougeot, Carole ULg; Kestemont, Patrick; Mélard, Charles ULg

Poster (2001)

Detailed reference viewed: 10 (1 ULg)
Peer Reviewed
See detailEffet of dietary fat levels on growth, feed efficiency and biochemical compositions of Eurasian perch Perca fluviatilis
Xu; Fontaine, P.; Mélard, Charles ULg et al

in Aquaculture International (2001), 9

Detailed reference viewed: 8 (2 ULg)
Full Text
Peer Reviewed
See detailSibling cannibalism in dorada under experimental conditions. I. Ontogeny, dynamics, bioenergetics of cannibalism and prey size selectivity
Baras, E.; Ndao, E.; Maxi, M. et al

in Journal of Fish Biology (2000), 57

Detailed reference viewed: 29 (13 ULg)
Peer Reviewed
See detailDynamics of total lipids and fatty acids during embryogenesis and larval developpement of Eurasian perch (Perca fluviatlis)
Abi-Ayad, Amine; Kestemont, P.; Mélard, Charles ULg

in Fish Physiology and Biochemistry (2000), 23

Detailed reference viewed: 8 (2 ULg)
See detailAquaculture
Kestemont, P.; Mélard, Charles ULg

in Craig, J. F. (Ed.) Percid Fishes: Systematics, Ecology and Exploitation (2000)

Detailed reference viewed: 33 (8 ULg)
Peer Reviewed
See detailSibling cannibalism in dorada under experimental conditions. II. Effect of initial size heterogeneity, diet and light regime on early cannibalism
Baras, E.; Maxi, M. Y.; Ndao, J. et al

in Journal of Fish Biology (2000), 57

Detailed reference viewed: 13 (3 ULg)
Peer Reviewed
See detailPhenotypic sex reversal of blue tilapia under constant and fluctuating thermal regimes, and its adaptive and evolutionary implications
Baras, E.; Prignon, Christian ULg; Gohoungo, G. et al

in Journal of Fish Biology (2000), 192

Detailed reference viewed: 15 (5 ULg)
Peer Reviewed
See detailThe effect of PIT tags on growth and physiology of age-0 cultured Eurasian perch Perca fluviatilis of variable size
Baras, E.; Malbrouck, C.; Houbart, M. et al

in Aquaculture (2000), 185

Detailed reference viewed: 9 (1 ULg)
Peer Reviewed
See detailCathepsin L in eggs and larvae of perch Perca fluviatilis: variations with developpement stage and spawning
Kestemont, Patrick; Cooremens, J.; Abi-Ayad, A. et al

in Fish Physiology and Biochemistry (1999), 21

Detailed reference viewed: 6 (0 ULg)