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See detailOtolith development in larval and juvenile European chub, Squalius cephalus: otolith shape analysis during ontogeny and daily increment validation
Bounket, Bernadette; Gibert, Pierre; Gennotte, Vincent ULiege et al

in Journal of Fish Biology (in press)

This study aimed to assess features of otoliths from laboratory-reared embryos, larvae and juvenile European chub, Squalius cephalus (Linnaeus 1758), from hatching to 180 days post-hatching (dph). We ... [more ▼]

This study aimed to assess features of otoliths from laboratory-reared embryos, larvae and juvenile European chub, Squalius cephalus (Linnaeus 1758), from hatching to 180 days post-hatching (dph). We observed the development of the three pairs of otoliths (lapilli, sagittae and asterisci) and more precisely shape changes, as well as timing and deposition rate of increments of the lapilli. The lapilli and the sagittae were present at hatching, whereas the asterisci formed between 20 and 30 dph. The lapillus and sagitta shapes were round until 20 dph. From 60 dph the anterior and the posterior rostra of the sagittae were well developed, but very thin, making this otolith too fragile to manipulate for further studies of shape and validation of otolith increment deposition rate. The lapilli provided reliable age estimates for free embryos, larvae and juveniles up to 120 dph. However, caution should be taken when ageing fish older than 150 dph as an underestimation was noticeable. The regression of the number of otolith increments on age showed a slope and an intercept not significantly different from 1 and 0, respectively, which indicated that otolith growth increments were deposited on a daily basis, with the first microincrement occurring at hatching. Increment counts were consistent between three interpreters, indicating a consistent and reliable age estimate. This study validates that the otolith increment deposition rate can be used to assess hatching dates and daily growth of wild age-0 S. cephalus under 150 dph and in environments similar to the conditions used in this study. [less ▲]

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See detailTemperature preference of Nile tilapia (Oreochromis niloticus) juveniles induces spontaneous sex reversal
Nivelle, Renaud ULiege; Gennotte, Vincent ULiege; Muller, Marc ULiege et al

in PLoS ONE (2019)

Nile tilapia (Oreochromis niloticus) is an African freshwater fish that displays a genetic sex determination system (XX|XY) where high temperatures (above 32°C to 36.5°C) induce masculinization. In Nile ... [more ▼]

Nile tilapia (Oreochromis niloticus) is an African freshwater fish that displays a genetic sex determination system (XX|XY) where high temperatures (above 32°C to 36.5°C) induce masculinization. In Nile tilapia, the thermosensitive period was reported from 10 to 30 days post fertilization. In their natural environment, juveniles may encounter high temperatures that are above the optimal temperature for growth (27–30°C). The relevance of the thermal sex reversal mechanism in a natural context remains unclear. The main objective of our study is to determine whether sexually undifferentiated juveniles spontaneously prefer higher, unfavorable temperatures and whether this choice skews the sex ratio toward males. Five full-sib progenies (from 100% XX crosses) were subjected to (1) a horizontal three-compartment thermal step gradient (thermal continuum 28°C– 32°C– 36.5°C) during the thermosensitive period, (2) a control continuum (28°C– 28°C– 28°C) and (3) a thermal control tank (36.5°C). During the first days of the treatment, up to an average of 20% of the population preferred the masculinizing compartment of the thermal continuum (36.5°C) compared to the control continuum. During the second part of the treatment, juveniles preferred the lower, nonmasculinizing 32°C temperature. This short exposure to higher temperatures was sufficient to significantly skew the sex ratio toward males, compared to congeners raised at 28°C (from 5.0 ± 6.7% to 15.6 ± 16.5% of males). The proportion of males was significantly different in the thermal continuum, thermal control tank and control continuum, and it was positively correlated among populations. Our study shows for the first time that Nile tilapia juveniles can choose a masculinizing temperature during a short period of time. This preference is sufficient to induce sex reversal to males within a population. For the first time, behavior is reported as a potential player in the sex determination mechanism of this species. [less ▲]

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See detailAquaponics as a sustainable way to diversify local food production in Belgium: an integrated study
Gennotte, Vincent ULiege; Forchino, Andrea Alberto; Rougeot, Carole ULiege et al

Conference (2019)

In aquaponics, fish wastes are transformed in valuable nutrients for soilless plant growth. Consequently aquaponics is often presented as a sustainable way to produce food. Initiatives and developing ... [more ▼]

In aquaponics, fish wastes are transformed in valuable nutrients for soilless plant growth. Consequently aquaponics is often presented as a sustainable way to produce food. Initiatives and developing projects are flourishing everywhere. However, the real environmental, economic and social sustainability of systems are usually difficult to objectify. We developed an aquaponics pilot unit with the aim to fill a part of the gap between science and market. This system is dedicated to data collection on the technical functioning and the balance between the different physical and biological compartments (nutrient, energy and water flows), on the environmental (LCA) and economic sustainability (LCC) and meant to integrate a real social and economic peri-urban network. In a second step, modelled data will be used for production system sizing and for technical, environmental and economic optimizing. [less ▲]

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See detailOtolith shape development in young-of-the-year chub (Cyprinidae, Squalius cephalus)
Gibert, Pierre; Bounket, Bernadette; Morat, Fabien et al

Poster (2018, April)

Only a very few studies have focused on the influence of age on the otolith morphometry of cyprinids. Chub Squalius cephalus (L.) is an abundant and widespread European rheophilic cyprinid. Otolith shape ... [more ▼]

Only a very few studies have focused on the influence of age on the otolith morphometry of cyprinids. Chub Squalius cephalus (L.) is an abundant and widespread European rheophilic cyprinid. Otolith shape analysis was used in many studies to characterize diverse local populations. In the present study we have evaluated the influence of age on the shape of otoliths during the early life of Chub when reared for experiment. Features of the sagittae, asterisci, and lapilli of laboratory-hatched larvae of the chub, were investigated until day 180 after hatching. Our observations showed that the lapilli and the sagittae were both present at hatching, whereas the asterisci were formed only between 20 and 30 days post-hatching. From day 45, the shape of the lapilli and the sagittae became more complex. The lapilli took the shape of a bean whereas the sagittae became far too fragile and inappropriate for study due to its developing very thin anterior and posterior rostra. From day 45, Fourier analysis of the shape of lapilli showed significant differences dependent on age group. However, the shape of the lapilli did not differ significantly between individuals of the same age group, even if their total length was different. This result suggested that differences in individual growth rate do not greatly influence the shape of the otolith. For young-of-the-year chub, according to the link between age and otolith shape, we recommend taking this parameter into account in any study aiming to highlight a genetic or environmental regulation of the otolith form. [less ▲]

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See detailEffect of high temperature on sex determinism and sex differentiation in African catfish Clarias gariepinus
Santi, Saïdou; Rougeot, Carole ULiege; Toguyeni, Aboubacar et al

Conference (2018)

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See detailApplication of the life cycle approach to the set-up of a pilot aquaponic facility in Belgium
Forchino, Andrea Alberto; Gennotte, Vincent ULiege; Mélard, Charles ULiege et al

Conference (2018)

Aquaponics is a technique which combines recirculating aquaculture systems with hydroponic cultivation. In the last decades aquaponics gained increasing attention as a sustainable way of producing fish ... [more ▼]

Aquaponics is a technique which combines recirculating aquaculture systems with hydroponic cultivation. In the last decades aquaponics gained increasing attention as a sustainable way of producing fish and vegetable for human consumption. However, previous studies, suggest that the environmental and economic sustainability of aquaponics is still a controversial subject matter. Flexible assessment tools such as Life Cycle Assessment (LCA) and Life Cycle Costing (LCC), allow one to investigate the whole process, from the design up to the operating phases. The aim of the present study is the combined application of LCA and LCC to highlight critical aspects related to the construction of an indoor pilot aquaponic facility in Belgium [less ▲]

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See detailEvolution de la forme des otolithes de juvéniles de chevaines (Cyprinidae, Squalius cephalus)
Gibert, Pierre; Bounket, Bernadette; Morat, Fabien et al

Poster (2018)

L’analyse de la forme des otolithes est utilisée pour caractériser diverses populations locales, mais seulement quelques études s’intéressent à l’influence de l’âge sur la forme des otolithes. Le Chevaine ... [more ▼]

L’analyse de la forme des otolithes est utilisée pour caractériser diverses populations locales, mais seulement quelques études s’intéressent à l’influence de l’âge sur la forme des otolithes. Le Chevaine Squalius cephalus (L.) est un poisson cyprinidé rhéophile très abondant et avec une large aire de répartition en Europe. Dans l’étude présentée, nous avons observé le lien entre l’âge et la forme des otolithes durant les premiers mois de la vie de Chevaines élevés en condition expérimentale. Les caractéristiques de forme des sagittae, asterisci, et des lapilli de chevaines éclos en laboratoire ont été étudiées jusqu’à l’âge de 180 jours post-éclosion. Nos observations montrent que les lapilli et les sagittae sont présents dès l’éclosion, alors que les asterisci sont formés entre 20 et 30 jours post-éclosion. A partir de 45 jours de vie post-éclosion, la forme des lapilli et des sagittae se complexifie. Les lapilli prennent une forme de haricots, tandis que les sagittae deviennent très fragiles avec le développement des rostres postérieur et antérieur. Ces observations nous confortent dans l’utilisation des lapilli, et non des autres paires d’otolithes, lorsqu’il s’agit d’études sur le chevaine s’appuyant sur de l’otolithométrie. A partir du jour 45 post-éclosion, les analyses de Fourier de la forme des lapilli montrent des différences significatives entre les classes d’âge. Cependant, au sein d’une même classe d’âge, la forme de l’otolithe n’est pas significativement différente, même entre des individus de longueur totale très différente. Ces résultats suggèrent que des taux différents de croissance individuelle n’influencent pas significativement la forme des otolithes. Pour des juvéniles de Chevaines, au regard du lien mis en évidence entre l’âge et la forme des otolithes, nous recommandons de prendre en compte ce paramètre dans le cas d’études ayant pour but de mettre en lumière l’effet de la génétique ou de l’environnement sur la forme des otolithes. [less ▲]

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See detailEco-designing Aquaponics: a case study of an experimental production system in Belgium
Forchino, Andrea Alberto; Gennotte, Vincent ULiege; Maiolo, Silvia et al

in Procedia CIRP (2018), 69

Aquaponics is receiving a growing interest as an emerging technology that combines recirculating aquaculture practices and hydroponics to produce fish and vegetables. However, a proper eco-design is ... [more ▼]

Aquaponics is receiving a growing interest as an emerging technology that combines recirculating aquaculture practices and hydroponics to produce fish and vegetables. However, a proper eco-design is essential to limit the environmental burdens and to enhance the economic profitability. Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) were here combined to estimate the environmental and economic impacts of a designed pilot indoor aquaponic system in Belgium. Results showed that energy consumption, infrastructure and water consumption represent the main critical issues to achieve both the environmental and economic sustainability of this aquaponic system. [less ▲]

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See detailTemperature Preference and Sex Differentiation in African Catfish, Clarias gariepinus
Santi, Saïdou; Rougeot, Carole ULiege; Toguyeni, Aboubacar et al

in Journal of Experimental Zoology. Part A, Ecological Genetics and Physiology (2017)

The African catfish Clarias gariepinus has a genetic sex determination system in which high temperature induces masculinization. The thermosensitive period for sex differentiation is short and occurs very ... [more ▼]

The African catfish Clarias gariepinus has a genetic sex determination system in which high temperature induces masculinization. The thermosensitive period for sex differentiation is short and occurs very early (from 6 to 8 days posthatching [dph]). As young juveniles can encounter high masculinizing temperature (36.5°C) in African water points, we aimed to determine the thermal preference of sexually undifferentiated juveniles and investigate if they spontaneously move toward high masculinizing temperature. Experiments were carried out in an environmental continuum (28–28–28°C and 28–32–36.5°C) made up of three 50-L aquariums connected together. Four hundred larvae from 10 different full-sib progenies were reared successively from 2 to 14 dph in these facilities. Before and after thermal treatments, fish were reared at 28°C until sex ratio determination at 70 dph. In the control continuum, fish were nearly equally distributed in the three compartments. Conversely, in the thermal continuum, compartment occupation significantly differed with progeny and period. During the highly thermosensitive period, two of five progenies significantly preferred (54.7% and 39.8% occupation) the 36.5°C compartment. All tested progenies reared in thermal continuum and separated 36.5°C aquarium showed a skewed sex ratio toward the male phenotype (78–100%). Nevertheless, no correlation was found between 36.5°C compartment occupation and sex ratio in thermal continuum groups. As masculinization temperature could be encountered in African water points during the spawning season, we discussed the adaptive advantage for the African catfish to display a sex differentiation process controlled by a temperature effect. [less ▲]

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See detailDo sex reversal procedures differentially affect agonistic behaviors and sex steroid levels depending on the sexual genotype in Nile tilapia?
Gennotte, Vincent ULiege; Akonkwa, Balagizi; Mélard, Charles ULiege et al

in Journal of Experimental Zoology. Part A, Ecological Genetics and Physiology (2017), 327(4), 153-162

In Nile tilapia Oreochromis niloticus, phenotypic males and females with different sexual genotypes (XX, XY, YY) have particular behavioural and physiological traits. Compared to natural XX females and XY ... [more ▼]

In Nile tilapia Oreochromis niloticus, phenotypic males and females with different sexual genotypes (XX, XY, YY) have particular behavioural and physiological traits. Compared to natural XX females and XY males, XY and YY females, and XX males expressed higher level of aggressiveness that could be related to higher levels of 17β-oestradiol and 11-ketotestosterone respectively. Our results suggest that the presence of a Y chromosome increases aggressiveness in females. However, since the same relationship between aggressiveness and the Y chromosome is not observed in males, we can hypothesize that the differences in aggressiveness are not directly dependent on the genotype but on the sex reversal procedures applied on young fry during their sexual differentiation to produce these breeders. These hormonal treatments could have permanently modified the development of the brain and consequently influenced the behaviour of adults independently of their genotype. In both hypotheses (genotype or sex reversal influence), the causes of behavioural modifications have to be searched in an early modification of the brain sexual differentiation. [less ▲]

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See detailLife cycle assessment (LCA) of an indoor pilot aquaponics production facility in Belgium
Gennotte, Vincent ULiege; Forchino, Andrea Alberto; Mélard, Charles ULiege et al

Poster (2017)

Aquaponics arouses a growing interest as a sustainable way to produce fish and vegetables in an integrated system. The main advantages of aquaponics production are water saving and reduced sewage that can ... [more ▼]

Aquaponics arouses a growing interest as a sustainable way to produce fish and vegetables in an integrated system. The main advantages of aquaponics production are water saving and reduced sewage that can be achieved through nutrient cycling. On the other side, several challenges raised from this method as it is energy demanding and often provides sub-optimal growing conditions for fish and/or vegetables in coupled systems (Junge et al., 2017). Sustainability of such systems must be assessed through a global approach taking into account not only the production processes but encompassing also upstream (structure and equipment) and downstream (product distribution and by-product valorisation) impacts. Life Cycle Assessment (LCA) is a method that can be used to investigate the sustainability of production systems such as aquaponics. We performed a full analysis of an aquaponics pilot system built in Belgium in 2017. The LCA covers the infrastructure construction, presently completed, and a prediction of system running based on a production model. [less ▲]

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See detailThermosensitivity of the sex differentiation process in the African catfish, Clarias gariepinus: Determination of the thermosensitive period
Santi, Saïdou ULiege; Gennotte, Vincent ULiege; Toguyeni, Aboubacar et al

in Aquaculture (2016), 455

Gonadal sex differentiation in gonochoristic fish is generally labile and under the control of two interacting processes: genetic sex determination (GSD) and environmental sex determination (ESD ... [more ▼]

Gonadal sex differentiation in gonochoristic fish is generally labile and under the control of two interacting processes: genetic sex determination (GSD) and environmental sex determination (ESD). Numerous experimental studies deal with temperature induced-sex differentiation in teleosts, but none focused on the African catfish Clarias gariepinus. The aim of this study was to confirm the thermosensitivity of the sex differentiation process and to determine the thermosensitive period during the African catfish development. Fish were exposed to high temperature (36 °C) for 3 days at different periods during ontogenesis. The treatment was applied every 3 days from fertilization until 29 days post-hatching (dph). Before and after the thermal treatment, fish were reared at 28 °C. Gonadal development was histologically characterized on fish sampled at 10, 15, 20, 25, 35, 45, 55 and 70 dph. Our results demonstrated that the African catfish displays a thermosensitivity of the sex differentiation process, with a masculinizing effect of high temperature (36 °C). The most thermosensitive period extended from 6 to 8 dph. Fish batches exposed to 36 °C during this period showed a sex-ratio skewed towards the male phenotype, ranging from 58 to 100% (high inter-familial variability). The African catfish gonads (male and female) stayed histologically undifferentiated until 20 dph. Obvious signs of gonadal differentiation clearly appeared at 25 dph in females and at 45 dph in males. Variability in sex-ratios between progenies and in the response to thermal treatment suggests a role of minor genetic factors and interactions between genomic and environmental determinants in the expression of the sexual phenotype. Statement of relevance: 1. This paper provides novel methods to control African catfish Clarias gariepinus sex differentiation through high temperature exposure and then to produce all-male populations. 2. Our work underlines the possibility to significantly reduce high temperature (masculinizing effect) treatment period to 3 days and consequently increase survival rate of progenies after treatment. 3. This study also shows the inter-family variability of thermosensitivity on the sex differentiation process in Clarias gariepinus. [less ▲]

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See detailIs adult translocation a credible way to accelerate the recolonization process of Chondrostoma nasus in a rehabilitated river?
Ovidio, Michaël ULiege; Hanzen, Céline; Gennotte, Vincent ULiege et al

in Cybium (2016), 40(1), 43-49

The decline of the patrimonial rheophilic nase, Chondrostoma nasus (Linnaeus, 1758) populations was mainly caused by construction of dams and hydroelectric power-plants, together with the straightening ... [more ▼]

The decline of the patrimonial rheophilic nase, Chondrostoma nasus (Linnaeus, 1758) populations was mainly caused by construction of dams and hydroelectric power-plants, together with the straightening and artificialization of the river banks and water pollution. In this study, we tested the hypothesis whether the translocation of few adult nase individuals from a river stretch to another upstream may be a credible way to accelerate the recolonization process of the species in the Amblève River (Southern Belgium). In February and March 2011, just before their spawning period, eight adult nases (462-509 mm; 1546-2002 g; presumed males and females) were captured in the lower part of the River Amblève. Fin clip samples were stored in alcohol for further genetic analysis. They were equipped with a 14 g radio transmitter and translocated upstream in a 18 km river stretch, where the species had disappeared since decades due to river anthropization. They were manually located two to five times/week using mobile receivers until maximum June 2012 (n = 977 locations). River temperature and flow were hourly recorded during the entire tracking period. The tagged nase individuals displayed various mobility patterns, exploited different areas of the river stretch, occupied longitudinal home ranges from 3.4 to 36.1 km (one individual finally left the new river stretch) and travelled total distances from 12.2 to 186.6 km. The tagged individuals were most of the times apart from one to another, but most individuals grouped together in potential spawning areas in late March-early April 2011, suggesting an attempt to reproduce. In September 2011, electric fishing in two potential detected spawning sites allowed to capture 16 juvenile (0+) nases, demonstrating the existence of spawning activity in the newly occupied river stretch. Individual genetic characterization was performed in 2014 in order to reveal a possible direct lineage between juveniles and adults. Allelic distribution of 22 microsatellite markers unambiguously identified the 16 juveniles as full-sib progeny descending from two of the translocated adults. This demonstrated that the adult nases succeeded to find spawning areas and that progeny found raised-up from the translocated individuals. [less ▲]

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See detailL'élevage du hotu en Wallonie
Gennotte, Vincent ULiege; Prignon, Christian ULiege

Book published by Les Presses Agronomiques de Gembloux (2016)

Ce document décrit les techniques d’élevage du hotu, parcourant la reproduction, l’élevage larvaire et le grossissement des juvéniles, dans différentes conditions de production. Il constitue la synthèse ... [more ▼]

Ce document décrit les techniques d’élevage du hotu, parcourant la reproduction, l’élevage larvaire et le grossissement des juvéniles, dans différentes conditions de production. Il constitue la synthèse des résultats d’un programme de recherche mené par le Centre de Formation et de Recherche en Aquaculture (CEFRA, Université de Liège), et financé par le Service Public de Wallonie et le Fonds Européen pour la Pêche, visant à développer les techniques d’élevage de cette espèce dans le cadre d’un programme plus vaste de restauration des populations piscicoles patrimoniales de Wallonie. Ces résultats ont été complétés par les connaissances issues de recherches antérieures pour constituer un guide technique le plus complet possible, destiné au pisciculteur intéressé par la production de nouvelles espèces. [less ▲]

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See detailL'élevage du barbeau en Wallonie
Gennotte, Vincent ULiege; Prignon, Christian ULiege

Book published by Les Presses Agronomiques de Gembloux (2016)

Ce document décrit les techniques d’élevage du barbeau, parcourant la reproduction, l’élevage larvaire et le grossissement des juvéniles, dans différentes conditions de production. Il constitue la ... [more ▼]

Ce document décrit les techniques d’élevage du barbeau, parcourant la reproduction, l’élevage larvaire et le grossissement des juvéniles, dans différentes conditions de production. Il constitue la synthèse des résultats d’un programme de recherche mené par le Centre de Formation et de Recherche en Aquaculture (CEFRA, Université de Liège), et financé par le Service Public de Wallonie et le Fonds Européen pour la Pêche, visant à développer les techniques d’élevage de cette espèce dans le cadre d’un programme plus vaste de restauration des populations piscicoles patrimoniales de Wallonie. Ces résultats ont été complétés par les connaissances issues de recherches antérieures pour constituer un guide technique le plus complet possible, destiné au pisciculteur intéressé par la production de nouvelles espèces. [less ▲]

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See detailEtude de la diversité génétique et de l’état des stocks des populations de barbeaux et de hotus en Wallonie. Amélioration des techniques d’élevage en vue de repeuplements raisonnés et de transferts de connaissances vers les pisciculteurs
Gennotte, Vincent ULiege; Prignon, Christian ULiege; Dierckx, Arnaud ULiege et al

Report (2015)

Nase (Chondrostoma nasus) and common barbel (Barbus barbus) are two rheophilic cyprinid fish naturally present in South Belgian rivers. During the last decades, the construction of dams together with ... [more ▼]

Nase (Chondrostoma nasus) and common barbel (Barbus barbus) are two rheophilic cyprinid fish naturally present in South Belgian rivers. During the last decades, the construction of dams together with changes in hydrological regimes, modifications of riverbed morphology and water pollution caused some local dramatic declines in their populations. However, recent improvements in terms of water quality and habitat fragmentation allow now to implement a rational restocking plan of locally endangered patrimonial fish species such as nase and common barbel. To reach this goal, this project (co-funded by the European Fisheries Fund and the Wallonia Public Service) proposed to develop five complementary parts with specific objectives: • Review of the knowledge on nase and barbel geographical distribution and stock health in Wallonia. This section presents the distribution and recent evolution of populations in Europe, and more specifically in Wallonia. Areas where population declines were reported are identified. Even if a weak population expansion was reported in some isolated cases, the global status of Walloon populations is still concerning. • Characterization of genetic structure and diversity of South Belgium populations. Restocking operations for a conservation purpose have to be based on the knowledge and the use of wild type genetic strains. Nase and barbel populations from South Belgium were genetically characterized by use of microsatellites. Globally, nase and barbel populations are structured on a basin scale. A slight genetic differentiation exists between populations from the Rhine basin and the Meuse basin, defining two conservation units, but no finer structure was observed among populations from the Meuse basin. Genetic variation was high within populations. Genetic structure of barbel populations is more complex due to past restocking operations with different genetic lineages. An analysis of mDNA identified 6 different haplotypes but was unable to categorize them as autochtone or allochtone. • Development of fish production techniques. The complete control of fish farming is necessary to produce high quality juveniles for restocking. All the steps of the production cycle were addressed: broodstock management and reproduction, egg incubation, larval rearing and grow-out. Production systems ranging from extensive pond culture to intensive RAS were tested and the optimal farming conditions were identified (temperature, density, feeding, tank volumes, …). • Adaptation assessment of farmed fingerlings to natural conditions. Growth and survival performances of captive farmed fish were assessed in an experimental environment that mimics natural conditions. The results suggested that the more efficient practice for restocking would be based on operations performed in spring with large juveniles (3 to 50 g). • Know-how diffusion toward fish farmers. All the breeding and grow-out techniques developed for nase and barbel production are the subject of two handbooks. These documents, attached to the report, will be published and distributed to fish producers. [less ▲]

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See detailBrief exposure of embryos to steroids or aromatase inhibitor induces sex reversal in Nile tilapia (Oreochromis niloticus)
Gennotte, Vincent ULiege; Mafwila Kinkela, Patrick ULiege; Ulysse, Bernard et al

in Journal of Experimental Zoology. Part A, Ecological Genetics and Physiology (2015), 323

This study aimed to develop sex reversal procedures targeting the embryonic period as tools to study the early steps of sex differentiation in Nile tilapia with XX, XY and YY sexual genotypes. XX eggs ... [more ▼]

This study aimed to develop sex reversal procedures targeting the embryonic period as tools to study the early steps of sex differentiation in Nile tilapia with XX, XY and YY sexual genotypes. XX eggs were exposed to masculinizing treatments with androgens (17α-methyltestosterone, 11-ketotestosterone) or aromatase inhibitor (Fadrozole), whereas XY and YY eggs were subjected to feminizing treatments with estrogen analog (17α-ethynylestradiol). All treatments consisted of a single or double 4-h immersion applied between 1 and 36 h post-fertilization (hpf). Concentrations of active substances were 1000 or 2000 µg l-1 in XX and XY, and 2000 or 6500 µg l-1 in YY. Masculinizing treatments of XX embryos achieved a maximal sex reversal rate of 10 % with an exposure at 24 hpf to 1000 µg l-1 of 11-ketotestosterone or to 2000 µg l-1 of Fadrozole. Feminization of XY embryos was more efficient and induced up to 91 % sex reversal with an exposure to 2000 µg l-1 of 17α-ethynylestradiol. Interestingly, similar treatments failed to reverse YY fish to females, suggesting either that a sex determinant linked to the Y chromosome prevents the female pathway when present in two copies, or that a gene present on the X chromosome is needed for the development of a female phenotype. [less ▲]

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See detailGenetic structure of nase, Chondrostoma nasus, and common barbel, Barbus barbus (Teleostei, Cyprinidae) populations in South Belgium rivers: toward a rational management of conservation restocking
Gennotte, Vincent ULiege; Michaux, Johan ULiege; Prignon, Christian ULiege et al

Poster (2014, December)

Nase (Chondrostoma nasus) and common barbel (Barbus barbus) are two rheophilic cyprinid fish naturally present in the Belgian Meuse and Rhine basins. During the last decades, the construction of dams ... [more ▼]

Nase (Chondrostoma nasus) and common barbel (Barbus barbus) are two rheophilic cyprinid fish naturally present in the Belgian Meuse and Rhine basins. During the last decades, the construction of dams together with changes in hydrological regimes, modifications of riverbed morphology and water pollution have caused some local dramatic declines in their populations. However, recent improvements in terms of water quality and habitat fragmentation allow considering as realistic a rational restocking plan of locally endangered patrimonial fish species such as nase and common barbel. Restocking operations for a conservation purpose have to be based on the knowledge and the use of wild type genetic strains. Therefore, the aim of this study was to characterize the genetic structure and diversity of nase and common barbel populations in South Belgium rivers. Wild common barbels (n = 313) and nases (n = 271) were sampled by electrofishing in respectively 10 and 6 different tributaries from the Meuse and Rhine rivers. Genotyping was performed on 24 microsatellite markers for each species. Preliminary results showed, for both species, a differential genetic clustering between fish originating from the Meuse basin and those originating from the Rhine basin. Detailed analysis describing the genetic structure and diversity of South Belgium populations will be presented and will serve as a management tool to set up a breeding plan for conservation restocking. [less ▲]

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