http://popups.uliege.be/2984-0317/index.php?id=249 Numéros en texte intégral fr ven., 19 janv. 2024 10:38:34 +0100 ven., 19 janv. 2024 10:38:34 +0100 http://popups.uliege.be/2984-0317/index.php?id=249 0 http://popups.uliege.be/2984-0317/index.php?id=638 ven., 26 janv. 2024 15:27:52 +0100 http://popups.uliege.be/2984-0317/index.php?id=638 http://popups.uliege.be/2984-0317/index.php?id=697 lun., 29 janv. 2024 16:02:51 +0100 http://popups.uliege.be/2984-0317/index.php?id=697 http://popups.uliege.be/2984-0317/index.php?id=698 lun., 29 janv. 2024 16:03:42 +0100 http://popups.uliege.be/2984-0317/index.php?id=698 http://popups.uliege.be/2984-0317/index.php?id=783 mar., 30 janv. 2024 10:04:03 +0100 http://popups.uliege.be/2984-0317/index.php?id=783 http://popups.uliege.be/2984-0317/index.php?id=784 The agonistic behaviour of Astatotilapia brownae (endemic species of cichlid teleost in lake Victoria) was studied. Three different colored patterns were observed. Each of them was shown to correspond to an individual motivation condition. When analysed, the agonistic behaviour appeared to include five distinct movements. The temporal association of the behaviour sequences was approached 1° by a diagram description of the sequences and 2° by quantifying the relationships between them using the statistics x2 method. Despite a reduced series of coloration pattems , A. brownae may be characterized by a highly developped ritualisation of its agonistic behaviour. By comparison with other cichlid species (different geographic origin and,/or different reproduction strategy), the present work allows better and more complete characterizarion of A. brownae. Ce travail consiste en une étude du comportement agonistique d' Astatotilapia brownae, un poisson cichlidé endémique du lac Victoria. Trois patrons de coloration correspondant chacun à un état de motivation bien déterminé ont été observés. Le comportement agonistique a été analysé. Il comporte cinq mouvements distincts. L'association temporelle des séquences comportementales a pu être mise en évidence par la description en diagramme de séquences et la quantification des liens qui les unissent par la méthode 762. Malgré une faible gamme de patrons de coloration, A. brownae présente une ritualisation très développée au niveau du comportement agonistique. Une comparaison avec d'autres espèces de cichlidés de répartition géographique et/ou de stratégie de reproduction différente permet de mieux situer A. brownae. mar., 30 janv. 2024 10:04:43 +0100 http://popups.uliege.be/2984-0317/index.php?id=784 http://popups.uliege.be/2984-0317/index.php?id=786 In 1988, our laboratory started the « Salmon 2000 Project », aiming at the reconstitution of populations of Atlantic salmon (Salmo salar L.) in the River Meuse basin, where the species had disappeared since the 1930's. This paper presents the first results on the biology of a reconstructed salmon population at Esneux, in the River Ourthe, one of the main tributaries of the River Meuse. On June 12th, 1989, 1,000 salmon parrs were restocked in this station, averaging 46 mm (fork length) and 1,0 g of body weight. 80 days later, 60 individuals were captured by electrofishing at their site of release. Their lengths ranged from 70 to 135 mm (mean = 101 mm) and the average weight was 12,3 g, after 80 days at a mean water temperature of 18,55 "C. We used three methodologies based on microhabitat and mesohabitat concepts to determine the preferences of salmon parrs towards river habitat characteristics, and to define a strategy aiming at a comparative study of habitat segregation among rheophilous species. The habitat study shows that salmon parrs exploit preferentially riffle areas (mean slope = I ,55 cm/m), on a substrate principally composed of cobbles ( 1 0-20 cm). The densities ranged from 0 to 16 parrs/100 m2 and were statistically (p < 0.05) and positively correlated with the proportions of depth class 20-40 cm and bottom current speed class 50-70 cm/s. These results are similar to those obtained on natural populations of Atlantic salmon living in comparable waterbodies and tend to prove the good adaptation of the reconstructed population in the River Ourthe. From this first field experiment, methodological aspects and new research perspectives and axes are discussed. mar., 30 janv. 2024 10:05:21 +0100 http://popups.uliege.be/2984-0317/index.php?id=786 http://popups.uliege.be/2984-0317/index.php?id=788 20 female tilapias of genetic interest were individually marked with transponders (passive radio-frequency identification tags). Transponders were implanted into the dorsal muscles or into the body cavity of the fishes. After a 30 days delay, a 100 % retention level was observed, using a compatible radio-frequency reading system. This technic could be applied in other fish species of scientific or commercial interest. Nous avons marqué individuellement 20 femelles tilapia (appartenant à des souches génétiquement sélectionnées) au moyen de micro-marques (« transponders ») injectées dans la musculature dorsale ou dans la cavité péritonéale. Ces marques sont contrôlées électroniquement. Nous avons observé 100 % de rétention après 30 jours. Cette technique pourrait être appliquée à d'autres espèces d'intérêt scientifique ou commercial. mar., 30 janv. 2024 10:05:54 +0100 http://popups.uliege.be/2984-0317/index.php?id=788 http://popups.uliege.be/2984-0317/index.php?id=789 During two years, four experimental groups of male and female barbels were submitted to controlled photoperiods, allowing a production of larvae nearly all the year round. Reared barbels were used for experimental and restocking purposes. Pendant deux ans, nous avons soumis quatre lots expérimentaux de barbeaux mâles et femelles d'élevage à différentes photopériodes artificielles, permettant une production quasi continue de larves. Celles-ci ont été élevées en eau réchauffée et utilisées pour l'expérimentation en génétique, le repeuplement des rivières et la commercialisation. mar., 30 janv. 2024 10:06:28 +0100 http://popups.uliege.be/2984-0317/index.php?id=789 http://popups.uliege.be/2984-0317/index.php?id=791 The paper deals with the 1983-1989 results of a barbel stocking programme carried on in the running waters of Southern Belgium (Wallonia). Barbel used as stocking material were produced by artificial spawning of wild and hatchery-reared brood-stocks. Fry, fingerlings and sub-adult fish were cultivated at optimum temperature (18-24°C) in ponds and tanks supplied with a heated effluent (Tihange nuclear power plants on the R. Meuse). For the period 1983-1989, 85,495 barbels (3,553 kg) of all sizes (4-50 cm) were stocked in 14 streams, in order either to rebuild extincted populations (as in the R. Méhaigne) or to sustain declining ones (as in the R. Meuse). Stocking performed in the R. Méhaigne resulted in the rebuilding of high density (50-100 kg/ha) populations contributing to over 50% of total ichthyomass in several stations. Barbel stocked in early June at a size of 11-12 cm (22 g) attain a size of 10.0-16.8 cm, 19.3 -21.4 cm and 23.8-24.9 cm at the end of their first, second and third summer season, respectively. The average annual survival rate of the stocked barbel is 56%. Angler's catches (legal size = 27 cm fork length) amount to a minimum value of 14.6% of the number of catchable fish available. Most (62%) tagged > 20 cm barbel stay within a +- 0.2 km river stretch but some fish (3.2%) move over long distance (2 km and over). Hatchery-reared barbel acclimatizised in the R. Méhaigne were proven to spawn naturaly in May-June, 1989 and to produce wild fry and fingerlings. Growth studies performed on tagged > 20 cm barbel stocked in the R. Meuse indicate that a 30 cm long fish at release attains a size of 35 cm after 1 year and 40 cm after two years. Recapture rates by anglers are relatively low (maximum 6.2% in one station) and 15.8% of the catch is composed of barbel having spent over 400 days in the river. Analysis of angler's recapture reveals a high proportion (62%) of tagged barbels moving over distances > 1km (maximum recorded = 14.5 km) from their point of release. Most movements are in an upstream direction (towards the fast flowing and turbulent water zones just below navigation weirs) or towards the lower course of tributaries offering gravel spawning grounds. As a conclusion, the experimental stocking of Southern Belgian running waters with hatchery-reared barbels has produced very positive results both in term of ecology (rebuilding of extincted populations, as in the R. Mehaigne) and sport angling (increased catch, as in the R. Meuse). In the future, this type of stocking may be continued and even extended provided that the rearing technologies used allow high quality fish (geneticaly and behaviouraly) to be produced. Nevertheless, a long term preservation of the barbel ecological and fishery resource can only be achieved by taking measures to conserve, improve or restore natural habitats, to increase the success of natural reproduction and recuitment and to reduce the angling pressure (mortality) on large late-maturing (> 35 cm and 8 years) females. mar., 30 janv. 2024 10:07:01 +0100 http://popups.uliege.be/2984-0317/index.php?id=791