Impact assessment and remediation of anthropogenic interventions on fish populations - (FISHGUARD)

Report (2006)

The disruption of longitudinal river connectivity by man-made obstacles and the stocking of fish communities with non-indigenous species or genotypes threaten the fish fauna of Belgian rivers to various ... [more ▼]

The disruption of longitudinal river connectivity by man-made obstacles and the stocking of fish communities with non-indigenous species or genotypes threaten the fish fauna of Belgian rivers to various extents. Obstacles impede migrations between habitats that are vital for populations, and they may restrict the gene flow between populations, thereby reducing the effective size and genetic diversity of populations and increasing the risk of local extinction. Restocking programs often involve the introduction of non-indigenous genotypes in native populations. Moreover, although stocking programs lead to the temporal and superficial enrichment of local fish communities or gene pools, they generally result in a loss of biodiversity on a regional or international scale through the homogenisation of communities and the breakdown of genetic differentiation between populations. Thus, stocking programs cannot compensate for the loss of free migration by artificial obstructions. The impact of these changes on fish populations remains largely unknown, which complicates the priorisation of spots to preserve and spots to restore. Here, we present an integrated study on Belgian waters, both in Flanders and Wallonia, which analyses fish communities, gene flow and migration patterns in the field, as well as the swimming and leaping performances of fishes under controlled conditions. [less ▲]

Movements and depth utilisation by the whithefish Coregonus lavaretus and Coregonus peled in a small artificial lake in eastern Belgium.

Poster (2005, June)

Using manual acoustic tracking our study quantified (1) the spatial distribution (2) the movement patterns and (3) the depth preference of adult whitefish in a small artificial lake of eastern Belgium ... [more ▼]

Using manual acoustic tracking our study quantified (1) the spatial distribution (2) the movement patterns and (3) the depth preference of adult whitefish in a small artificial lake of eastern Belgium were the species was introduced in 1978 for recreational fishing. From June to October 2004, n=6 C. lavaretus (LF 285-519 mm) were tracked (pingers and depth sensor transmitters) from a small boat over periods ranging from 98 to 108 days in Robertville Lake (elevation: 490 m; area: 63 ha; max. depth: 47 m). Whitefish were consistently mobile but showed quite variable lake use patterns. Two individuals traveled the entire length and breadth of the lake, whereas others remained in movement in the deep zone in the middle part of the lake or near the retaining dam wall. Whitefish occupied positions in the water column ranging from 2.6 to 27.0 m (mean 12.7 m ± 5.6 m) that varied depending on individuals. This first study on individual whitefish behaviour provides a better understanding of the behavioural ecology of the species in small artificial lake. [less ▲]

A 12-year study of the upstream migration of Anguilla anguilla in a fish-pass in the river Meuse reveals a dramatic decline of the stock in Belgium.

Conference (2005, April)

From 1992 to 2004 upstream migrating eels were collected in a trap (0,5 cm mesh size) installed at the top of a small pool-type fish-pass at the Visé-Lixhe dam (built in 1980 for navigation purposes and ... [more ▼]

From 1992 to 2004 upstream migrating eels were collected in a trap (0,5 cm mesh size) installed at the top of a small pool-type fish-pass at the Visé-Lixhe dam (built in 1980 for navigation purposes and hydropower generation; height : 8,2 m; not equipped with a ship-lock) on the international River Meuse near the Dutch -Belgium border (290 km from the North Sea; width: 200 m; mean annual discharge: 238 m3/s; summer water temperature 21-26°C).The trap in the fish-pass was checked continuously (three times a week) over the migration period from March to September each year, except in 1994. We caught a total number of 32157 eels (biomass 1,955 kg) with a size from 14 cm to 85 cm and a mean value of 31,6 cm corresponding to yellow eels. The study based on a constant year-to-year sampling effort revealed a regular decrease of the annual catch from a maximun of 5613 fish in 1992 to a minimum of 423 in 2004. This demographic trend is fitted by the equation: number per year = 5.614 - 299 t, where t is time in years with 1992 as year 1. According to this model, the upstream migrating yellow eelstock in the Belgian Meuse should drop to near zero within the next ten years, as an expression of a collapsing recruitment of glass eels in the estuary in the Netherlands. In the discussion of these results, we examine the possible role of two other factors on the decrease over time of the number of yellow eels caught in the fish-pass. i) the effect of environmental variables (river discharge, water temperature and dissolved oxygen content) on the timing and intensity of upstream migration waves and ii) the existence and use of alternative migration routes. [less ▲]

La pêche traditionnelle dans les pleines inondables du fleuve Ouémé au Bénin

in Cahiers d'Ethologie (2005), 22(2), 25-38

Artisanal gill-net fishery catches of the catfish, Schilbe intermedius (Tleostei:Schilbeidae), in two tributaries of the Ouémé River, Benin, West Africa

in African Journal of Aquatic Science (2005), 30(2), 163-166

Effects of a micro hydroelectric power plant upon population abundance, mobility and reproduction behaviour of European grayling T. thymallus and brown trout S. trutta in a salmonid river

in Garcia de Jalon, Diego; Vizcaino Martinez, Pilar (Eds.) International Symposium on Ecohydraulics. Aquatic habitat: Analysis & Restoration (2004)

This study examines the potential effects of a new micro hydroelectric power plant (MHPP) on the behaviour (habitat use, movements) and population abundance of European grayling (T. thymallus) and brown ... [more ▼]

This study examines the potential effects of a new micro hydroelectric power plant (MHPP) on the behaviour (habitat use, movements) and population abundance of European grayling (T. thymallus) and brown trout (S. trutta) in the Lhomme (Belgian Ardennes). Thirteen grayling and five brown trout were captured before their spawning period and were manually radio-tracked up to 6 times a week. Population density and biomass were estimated into two different sampling sectors with electric fishing, before and after the MHPP started up. The mobility patterns of grayling and trout in the reach of the river Lhomme influenced by the MHPP strongly contrasted with results obtained in an undisturbed river of the same type in the Belgian Ardennes. Movements were mostly restricted and rarely increased during the spawning period. Spawning took place, but was disturbed by hydropeakings. The population biomass of grayling and trout decreased by 61 % and 23 % respectively, five months after the start-up of the MHPP exploitation. [less ▲]

ETUDE DE LA REPARTITION SPATIALE ET DE LA DENSITE DE POPULATION DU HERON CENDRE DANS LA BASSE OURTHE AU PRINTEMPS 2004 COMME BASE A L'ESTIMATION DE LA PRESSION DE PREDATION EXERCEE SUR LE PEUPLEMENT DE POISSONS.

Report (2004)

En complément de l'étude approfondie du comportement de prédation du héron cendré sur le site hyper-attractif de la Meuse en aval du barrage de Lixhe, nous avons porté notre attention sur un tronçon de la ... [more ▼]

En complément de l'étude approfondie du comportement de prédation du héron cendré sur le site hyper-attractif de la Meuse en aval du barrage de Lixhe, nous avons porté notre attention sur un tronçon de la basse Ourthe entre Liège et Esneux où viennent s'alimenter au printemps des hérons probablement attachés à l'importante Colonie de Colonster. Dans ce milieu, l'objectif était de recenser les hérons selon une méthodologie standardisée : i) à différentes dates pendant la période de reproduction de l'espèce à Colonster qui s'étale de mars à mai et ii) en tenant compte de l'hétérogénéité du milieu au point de vue du degré d'antropisation et des possibilités d'expression par les hérons du répertoire des comportements de pêche typiques et atypiques mis en évidence dans la Meuse à Lixhe. [less ▲]

LE COMPORTEMENT DE PREDATION DU HERON CENDRE DANS LA MEUSE EN AVAL DU BARRAGE DE LIXHE EN MARS -MAI 2004

Report (2004)

Au printemps, la Meuse en aval du barrage de Visé-Lixhe (fig. 1) est un important lieu d'alimentation des hérons cendrés vraisemblablement attachés à la héronnière de Lanaye (une cinquantaine de couples ... [more ▼]

Au printemps, la Meuse en aval du barrage de Visé-Lixhe (fig. 1) est un important lieu d'alimentation des hérons cendrés vraisemblablement attachés à la héronnière de Lanaye (une cinquantaine de couples reproducteurs en 2004; voir Annexe 1) située en aval et à celle de Vivegnis située en amont (Jacobs et al., 2003). Par ailleurs, le site de Lixhe offre des conditions d'observation exceptionnelles pour réaliser une étude détaillée du comportement de prédation de l'espèce. C'est ce type d'étude qui a été entreprise au printemps 2004 avec un double objectif: d'une part, améliorer les connaissances sur la biologie du héron cendré dans nos régions, notamment en terme d'écologie comportementale (répertoire des comportements alimentaires, relations prédateurs-proies, incidence sur le peuplement en poissons) et, d'autre part, tester une méthodologie d'étude transposable à des sites comparables et spécialement à des piscicultures. [less ▲]

Long range seasonal movements of northern pike (Esox lucius L.) in the barbel zone of the River Ourthe (River Meuse basin, Belgium).

Conference (2003, June)

In order to study the annual activity cycle and reproductive ecology of northern pike (Esox lucius L.) in the River Ourthe (Belgian Ardenne), 6 fish (579-742mm FL, 1605-4090g, 2 females and 4 males) were ... [more ▼]

In order to study the annual activity cycle and reproductive ecology of northern pike (Esox lucius L.) in the River Ourthe (Belgian Ardenne), 6 fish (579-742mm FL, 1605-4090g, 2 females and 4 males) were captured by electric fishing in November 2000 and January 2001. They were surgically implanted with a radio-transmitter and tracked for 149 to 349 days in a 30-km river stretch. During the pre-spawning period in winter, most movements were between distinct holding areas spaced from 40 to 550 m. All the pike began the upstream spawning migration between 8 February and 30 March 2001, when the mean water temperature varied from 6.7°C to 8.7 °C and the water flow from 52 to 199 m3s-1. The six pike travelled upstream, over distances ranging from 0.75 km to 15.7 km to reach their potential spawning sites. Pike arrived on their potential spawning sites between the 13 February and the 02 April 2001 and remained there from 5 to 25 days when the daily mean water temperature ranged from 2.9 to 10.0 °C. The six pike moved downstream after spawning and showed similar behaviour to those observed prior to spawning, but the distances between holding areas were more extended than during the winter pre-spawning period. When considering the entire tracking period, the longitudinal extension of the activity domains ranged 1 421 to 24 798 m (mean 12,050 m). This exploratory study provided original observations on northern pike movements in a barbel zone of the River Meuse basin. Results contrasted with the widely established view of pike being a sedentary predator and provides data on its behaviour throughout the annual cycle. [less ▲]

Etudes des impacts hydrauliques, sédimentologiques et écologiques liés aux travaux hydrauliques sur la Semois

in Belgeo (2003), 3

Cette étude tente d’évaluer les impacts des dragages réalisés dans le bassin de la Semois (Ardenne). Cette étude interdisciplinaire se penche sur les aspects hydrauliques, environnementaux ... [more ▼]

Cette étude tente d’évaluer les impacts des dragages réalisés dans le bassin de la Semois (Ardenne). Cette étude interdisciplinaire se penche sur les aspects hydrauliques, environnementaux, géomorphologiques et sédimentologiques. [less ▲]