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See detailDynamics of upstream movements of the European eel Anguilla anguilla in an inland area of the River Meuse over the last 20 years
Nzau Matondo, Billy ULg; Ovidio, Michaël ULg

in Environmental Biology of Fishes (2016), 99

The dynamics of upstream movements of the yellow eel Anguilla anguilla were investigated at Lixhe on the Belgian River Meuse in an inland fish pass regularly monitored from 1992 to 2014. Based on a ... [more ▼]

The dynamics of upstream movements of the yellow eel Anguilla anguilla were investigated at Lixhe on the Belgian River Meuse in an inland fish pass regularly monitored from 1992 to 2014. Based on a constant year-to-year sampling effort, we examined the abundance of ascending yellow eels and their body size, seasonal movement, and the associated water temperature and flow. Over the last 23 years, the number of ascending yellow eels has declined at an average 4.2% per year since 1992. The abundance of eels in 2014 is estimated at 4.5% of the ascending stock in 1992. We observed that some annual variations in eel abundance at Lixhe might be related to opening fish passes downstream of the study site. The results clearly demonstrated that long-term declining abundance of eels has resulted in increased sizes (mean increase, 4.1 mm per year since 1992) and temperatures triggering the upstream movement process (1.03°C per decade), with earlier dates for the last eel passages reducing the difference between temperature extremes of eel passages through the fish pass during the migration season. Eel movements occurred in spring and summer at low river discharge and were mainly triggered by high-temperature events. Eels have become larger with time because of improved feeding opportunities and more growth habitats available resulting from the long-term reduction in recruitment. This study highlights the importance of investigating long time spans for a better comprehension of the changes observed in yellow eels and for the optimization of management measures and future research. [less ▲]

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See detailAssessment of the entering stock, migration dynamics and fish pass fidelity of european eel in the belgian meuse river
Nzau Matondo, Billy ULg; Benitez, Jean-Philippe ULg; Dierckx, Arnaud ULg et al

in River Research & Applications (2016)

Migration dynamics of incoming eels in Belgium via Lixhe in the Meuse River were investigated using two fish passes with different configurations— net traps and automatic detection stations—as tools to ... [more ▼]

Migration dynamics of incoming eels in Belgium via Lixhe in the Meuse River were investigated using two fish passes with different configurations— net traps and automatic detection stations—as tools to distinguish resident and migrating eels. From April to September 2013, 435 eels (P50 length, 403 mm; range, 196–836 mm) were caught (daily maxima catch, 90 eels per day), 90% between 13 June and 1 August (50 days) and P50 on 19 July. Eels migrated mostly at 19–26 °C (P50, 24.4 °C), river discharge 65–314m3 s 1 (P50, 84m3 s 1), during the dark at 00:00–05:00 h and during both the waxing and waning phases of moonlight. From 396 eels tagged and released 0.3 km downstream of the Lixhe dam, 6.8% of them were recaptured, and 37.4% were detected. Migration flux was estimated at 7184 eels (0.863 t) using the markrecapture method and decreased to 1156 eels (0.139 t) using automatic transponder detection. Most eels probably migrated through a sluice located downstream of Lixhe to reach the upper Meuse via the Albert Canal. Eels moved almost independently to the configuration of the fish passes and their location, but most eels displayed fidelity to the fish pass where they were captured. Migrant eels showed a wide range of size and life stages, with a higher proportion of eels (80%) belonging to the yellow eel stage. A lower proportion of eels (6%) had a larger size and presented an advanced continental silvering process corresponding to the migrating stage before their transatlantic migration. Copyright © 2016 John Wiley & Sons, Ltd. [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 ULg; Hanzen, Céline; Gennotte, Vincent ULg 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 detailRecent decline of roach Rutilus rutilus stock in a large river ecosystem in relation with its population dynamics
Otjacques, William; Latli, Adrien; Bernard, Benoît et al

in Fundamental and Applied Limnology (2015), 187(2), 151-163

Studies dealing with quantitative decline of freshwater fish species with long-time series data are rather scarce and primarily limited to migratory species. We present an original work integrating over ... [more ▼]

Studies dealing with quantitative decline of freshwater fish species with long-time series data are rather scarce and primarily limited to migratory species. We present an original work integrating over two decades investigations on roach (Rutilus rutilus L.) stock, one of the dominant cyprinid fish species in the River Meuse (Belgium). This study aimed to quantify changes in the stock of roach after recent indicators (captures from sport fishermen) suggested a sharp decline. Three methods were used: capture-mark-recapture (CMR) estimation, catch per unit of effort by gillnetting (CPUE) and long-term monitoring of fish-passes. Population dynamics of roach was also investigated. CMR method demonstrated a decrease of 91% of the roach stock compared to earlier data (1993–2003), with current densities close to 300 roach ha–1. This was also confirmed by a decrease of 95 % in CPUEs and a decrease between 93 and 98 % in two fish-passes during the same period. On the other hand, growth and mortality did not indicate radical changes before and after the decline was found. As roach stock decline is generalizable to the whole Belgian’s Meuse following estimations in two other sites, further investigations are needed to explain the reasons underlying this decline in order to take conservation measures. First, the uptake of primary production (i.e. phytoplankton) by invasive clams is supposed. And secondly, an increase in predation pressure by the Great Cormorant is effective as this avian predator was found in high densities from 2000 until 2006. [less ▲]

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See detailAn overview of potamodromous fish upstream movements in medium-sized rivers, by means of fish passes monitoring
Benitez, Jean-Philippe ULg; Nzau Matondo, Billy ULg; Dierckx, Arnaud ULg et al

in Aquatic Ecology (2015), 49(4), 481-497

This study aims to investigate the upstream movement patterns of potamodromous fish species using multi-annual monitoring of modern multi-species fish passes in two medium-sized Belgian rivers: the ... [more ▼]

This study aims to investigate the upstream movement patterns of potamodromous fish species using multi-annual monitoring of modern multi-species fish passes in two medium-sized Belgian rivers: the Berwinne and the Amble`ve. During a 6-year monitoring period including a frequency of 1–5 times per week, the captured individuals were identified, measured and weighed to determine species abundance, and the periodicity of their seasonal movement patterns was investigated in relation to environmental factors. In the Amble`ve, 22 different fish species were monitored (n = 1513 individuals; biomass of 154 kg) and 14 species in the Berwinne (n = 3720; 408 kg). In both fish passes, inter-annual differences were observed, but the first year of monitoring was the best in terms of biomass, indicating the existence of an opening effect just after the fish passes opening, which allowed new migration routes. Salmonids and rheophilic cyprinids were predominant in terms of biomass, while minnow and spirlin were predominant in terms of number of fishes. The diversity in sizeranged from 46 to 760 mm demonstrating the importance of movements in various life stages. The capture periodicity showed different mobility patterns between the adult and juvenile stages in most species. Movements occurred frequently during the circus reproduction period for some species, but many species moved also apart from spawning period. This study highlights the omnipresence of patrimonial holobiotic potamodromous fish at different life stages that reflect their biological needs to move throughout the annual cycle. They must be considered as target species in river continuity restoration programmes and fish-pass design. [less ▲]

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See detailEvaluation de la qualité biologique des rivières wallonnes sur base des indices biologiques poissons. Support technique aux inventaires 2015.
Rimbaud, Gilles ULg; Ovidio, Michaël ULg; Dierckx, Arnaud ULg et al

Report (2015)

L’Université de Liège (LDPH) a effectué le travail décrit dans ce rapport pour le compte du Service public de Wallonie qui a financé ce projet dans le cadre d’une convention ayant pour objectif ... [more ▼]

L’Université de Liège (LDPH) a effectué le travail décrit dans ce rapport pour le compte du Service public de Wallonie qui a financé ce projet dans le cadre d’une convention ayant pour objectif l’évaluation de la qualité biologique des eaux de surface basée sur les indices biologiques « poissons » dans quatorze cours d’eau de Wallonie. Cette mission s’inscrit dans le contexte de la mise en oeuvre de la Directive 2000/60/CE établissant un cadre pour une politique communautaire dans le domaine de l’eau. [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 ULg; Prignon, Christian ULg; Dierckx, Arnaud ULg 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 detailShort-term responses of glass eels transported from UK to small Belgian streams
Ovidio, Michaël ULg; Tarrago-Bes, Frédérique; Nzau Matondo, Billy ULg

in Annales de Limnologie = International Journal of Limnology (2015), 51(3), 219-226

Restocking of inland waters with glass eels is one of the recovery options to prevent the decline of European eel Anguilla anguilla (L.) populations. We studied the growth, dispersion, density and habitat ... [more ▼]

Restocking of inland waters with glass eels is one of the recovery options to prevent the decline of European eel Anguilla anguilla (L.) populations. We studied the growth, dispersion, density and habitat preferences in the imported glass eels from United-Kingdom and stocked in three typologically different small Belgian streams, using electrofishing surveys around the single release point, 1 year following stocking. Our results clearly support that the recaptured individuals stocked in our streams farther from the sea, survived, grew, dispersed upstream and downstream. Elvers exploited the complete transversal section of stream, with preference for the sheltered microhabitats near the banks with slower water velocity and low depth. Length-weight relationship was different between streams in terms of allometric coefficient (b). We assume that microhabitats and food availabilities lead to contrasted results in terms of growth and absolute occurrence. Restocking of glass eels in small middle-land streams was found to be an interesting and unconventional option that requires adequate stream and habitat selection. [less ▲]

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See detailHistorical evolution of fish biodiversity and capture periodicity in the River Meuse (Belgium) as revealed by 15 consecutive years of fishpass monitoring
Benitez, Jean-Philippe ULg; Dierckx, Arnaud ULg; Nzau Matondo, Billy ULg et al

Conference (2015, June)

In the River Meuse at 323km upstream from the North Sea, the hydroelectric dam of Lixhe (rated power of 5300KW) is equipped with two fishpasses: one pool and weir fishpass (in operation since 1980; 0.13m³ ... [more ▼]

In the River Meuse at 323km upstream from the North Sea, the hydroelectric dam of Lixhe (rated power of 5300KW) is equipped with two fishpasses: one pool and weir fishpass (in operation since 1980; 0.13m³.s-1 operating flow) and one vertical slot fishpass (in operation since 1998; 1m3.s-1 operating flow). Both fishpasses were scientifically monitored using capture traps during 15 consecutive years (from 1999 to 2014). The objective of the study is to analyse i) the evolution of fish stock and biodiversity over 15 years and ii) the capture periodicity of fish and it’s variation over years. During the considered period, we observed 36 species at adult stage (88597 individuals with 75% of cyprinids) and 13 species at juvenile (0+) stage (335067 individuals with 90% of cyprinids). Global results between 1999 and 2014 showed a drastic reduction in capture per year (>90%) for some species like Anguilla Anguilla, Alburnus alburnus, Blicca bjoerkna, Rutilus rutilus and Tinca tinca. Whereas other species have emerged like Aspius aspius and Silurus glanis. For the 0+, an important interannual variation is observed from few individuals to several tens of thousands per year. The comparison between both fishpasses indicated a greater use (>50%) of the vertical slot fishpass by rheophilic species and species that have good swimming ability. The analysis of capture periodicity for the most abundant species at adult stage demonstrated the presence of stable behaviours between years for the Abramis abrama and B. bjoerkna respectively a Q50 of the capture day of the year from 108th to 144th day at mean=17°C and from 118th to 155th day at mean=18°C. In contrast other species have patterns more variables (Barbus barbus: Q50 from 96th to 266th day; R. rutilus: from 10th and 309th day). Finally the 0+ exhibited a capture periodicity stable in time during the summer. [less ▲]

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See detailDoes yellow eel prefer old pool and weir or new vertical slot fish pass during their upstream migration?
Nzau Matondo, Billy ULg; Dierckx, Arnaud ULg; Benitez, Jean-Philippe ULg et al

Conference (2015, June)

The hydroelectric dam of Lixhe in the River Meuse, 323km upstream from the North Sea at the entry of Belgium near the frontier with the Netherlands is equipped with two basin fish-passes: – the old pool ... [more ▼]

The hydroelectric dam of Lixhe in the River Meuse, 323km upstream from the North Sea at the entry of Belgium near the frontier with the Netherlands is equipped with two basin fish-passes: – the old pool-and-weir configuration (OFP) operates at low discharge (0.13m3/s) and – the new vertical-slot configuration (NFP) operating at high discharge (1m3/s) with attraction flow (1.5m3/s). However, the utilization rate of these fish-passes by the incoming yellow eels remains unknown, because the trap of NFP is not adapted to retain anguillids and small species. Yet, such knowledge is crucial to improve the inland colonization of the species and to increase our understanding of fish-pass utilization given its particular swimming mode. In season 2013, eels caught two times a week using a cone-trap pool in the OFP and net traps in the NFP, were tagged and released the same day 0.3km downstream (n = 396eels). The utilization of OFP and NFP was studied using automatic RFID transponder detection antennas placed in upstream basins of the fish-passes, during years 2013 and 2014. Results revealed that the OFP was the preferred migration route of eels (eel numbers, OFP:NFP, 2013= 88:51 and 2014= 41:16, χ²-test, p<0.0001), which was also used earlier in season. Eels displayed fidelity to their catch fish-passes (>70% of the detected eels, annually). Detection rate was high in the year of eel tagging (2013: 35.1%) before decreasing in the following year (2014: 14.4%). Eels used these fish-passes the night from 22:00 to 04:00, at 14-26°C, river flow <200m³/s and whenever waxing and waning phases of moonlight. Our results provide insight into the utilization of fish-passes by migrating eels. The study suggests further reflection before removing the old fish-pass in large rivers and to think about the eel attractiveness and comfort when the construction of a new fish pass is planned. [less ▲]

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See detailAssessing the passage of obstacles by fish. Concepts, design and application
Baudoin, Jean-Marc; Burgun, Vincent; Chanseau, Matthieu et al

Book published by Onema - Editeur: Véronique Barre (2015)

The fragmentation of habitats has been acknowledged for 30 years as one of the five main factors of biodiversity loss, in conjunction with pollution, overuse of natural resources, invasive species and ... [more ▼]

The fragmentation of habitats has been acknowledged for 30 years as one of the five main factors of biodiversity loss, in conjunction with pollution, overuse of natural resources, invasive species and climate change. Since then, public environmental policies have strived to restore the connectivity of natural habitats. That is particularly the case for water policy, which has made the ecological continuity of rivers a central element in policy planning, a quality element for monitoring programmes and one of the basic guidelines for river-basin management plans (RBMP). The time has thus come for decisions, with the resulting controversy given that any attempt to modify existing discontinuities impacts our perception of landscapes and various uses of aquatic environments. Given that there is, on average, at least one obstacle for every five kilometres of river in continental France, this issue concerns the entire country, its population and all water managers. That explains why it was necessary to have a single set of standardised procedures for selecting the work to be done on the basis of objective and comparable data. For the ecological continuity of fish, we now have the ICE method presented in this book, which describes obstacles in rivers and assesses the capacity of fish to overcome those obstacles during their upstream migration. The design, development and national deployment of this method required five years of intense, collective effort on the part of numerous scientists and the Onema local and regional offices. The method is the result of an outstanding multi-disciplinary approach involving both hydraulics and ecology, two disciplines that some people might see as irreconcilable, but that must work together synergistically in the effort to restore environments. The publication of this book in the Knowledge for action series marks the transition from the team that developed the method to the people who will use it to acquire better understanding of ecological continuity in rivers and as an operational tool in implementing water policy and enhancing biodiversity. [less ▲]

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See detailThe ICE protocol for ecological continuity: a new tool to evaluate the upstream fish passage success at physical barriers
Ovidio, Michaël ULg; Larinier, Michel; Burgun, Vincent et al

Conference (2015, June)

The recording and classification of obstacles that can interfere with the movements and migrations of fish is critical information to plan river restoration program. To date a major problem is to ... [more ▼]

The recording and classification of obstacles that can interfere with the movements and migrations of fish is critical information to plan river restoration program. To date a major problem is to determine the potential effect of each obstacle and to select the problematic sites that should be improved to restore longitudinal connectivity (construction of fish passage facilities, removal or modification of the obstacles). Fish passage success about an obstacle is complex and depends on the hydraulic conditions over and at the foot of the obstacle in relation to swimming and leaping capabilities of the fish species concerned. This selection and classification is too often biased because managers lack information’s on the fish capabilities to leap physical obstacles. The need for a simple, reliable and standardised assessment method for use by a wide range of environmental stakeholders rapidly became evident. We responded to the challenge and developed the ICE protocol as the basis for the required ecological-continuity assessment method, particularly in the context of the European Water Framework Directive implementation. The ICE protocol coordinated by ONEMA is based on an integration of the topographical and hydraulic characteristics of obstacles with the physical capabilities (swimming, jumping or crawling) of the fish species analysed. It requires the gathering of standardised descriptive variables on each obstacle. The result of the analysis is an indication on the risks of a structure constituting a more or less severe obstacle (5 classes) for a given fish species (n=47) or group of species. Particular attention was paid to the practical aspects of the method (time required and necessary human resources) to facilitate its use in a wide variety of situations and areas. Each procedure is presented as a flow chart to assist in decision-making, thus making the protocol easy to use for a wide range of people. [less ▲]

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See detailMarques actives utilisées en télémétrie "poissons"
Tétard, Stéphane; Ovidio, Michaël ULg; Capra, Hervé et al

Scientific conference (2015, April 03)

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See detailEstimation de l’abondance du stock des anguilles recrutées par migration de remontée dans la Meuse en Wallonie et réalisation des essais de repeuplement en juvéniles. Rapport final du projet financé par le Fonds européen pour la Pêche (Code projet: 32-1102-002)
Nzau Matondo, Billy ULg; Philippart, Jean-Claude ULg; Dierckx, Arnaud ULg et al

Report (2015)

Ce rapport final présente les résultats des recherches menées par le Laboratoire de Démographie des Poissons et d’Hydroécologie (LDPH) de l’Unité de Biologie du comportement dans le cadre d’un projet co ... [more ▼]

Ce rapport final présente les résultats des recherches menées par le Laboratoire de Démographie des Poissons et d’Hydroécologie (LDPH) de l’Unité de Biologie du comportement dans le cadre d’un projet co-financé par le Fonds Européen pour la Pêche (FEP) et le Service Public de Wallonie, Département de la Nature et des Forêts (code projet : 32-1102-002) intitulé «Estimation de l’abondance du stock des anguilles recrutées par migration de remontée dans la Meuse en Wallonie et réalisation des essais de repeuplement en juvéniles. » [less ▲]

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