-Obstacles in rivers are considered to be one of the main threats to diadromous fish. As a result of the recent collapse of the European eel, the European Commission introduced a Regulation, requiring to reduce all sources of anthropogenic mortality, including those caused by passing through hydropower turbines. Improving knowledge about migration triggers and processes is crucial to assess and mitigate the impact of obstacles. In our study, we tracked 97 tagged silver eels in a fragmented river situated in the Western France (the River Dronne). Using the movement ecology framework, and implementing a Bayesian state-space model, we confirmed the influence of river discharge on migration triggering and the distance travelled by fish. We also demonstrated that, in our studied area, there is a small window of opportunity for migration. Moreover, we found that obstacles have a significant impact on distance travelled. Combined with the small window, this suggests that assessment of obstacles impact on downstream migration should not be limited to quantifying mortality at hydroelectric facilities, but should also consider the delay induced by obstacles, and its effects on escapement. The study also suggests that temporary turbines shutdown may mitigate the impacts of hydropower facilities in rivers with migration process similar to those observed here.
This study describes the behaviour of radio-tagged returning Atlantic salmon, Salmo salar L., at the Golfech-Malause hydroelectric complex on the River Garonne, France. The particularity of this complex is that it is fitted with a fish lift, a type of fishway rarely tested for salmon. Only forty seven percent of salmon succeeded in passing. Frequenting of both the tailrace and the foot of the plant, where the lift was located, decreased rapidly during the blockage. Successful salmon spent proportionally more time near the entrance of the lift. The high mean number of visits to the lift entrance before upstream passage (51) suggested the lift was not sufficiently attractive. Evidence is also given of the difficulties specific to fish lifts that involve trapping fish: the V-shaped entrance of the fish lift holding pool could inhibit salmon without even guaranteeing a non-return effect.
Résumé. -L'état physiologique des poissons a été estimé, pour une part, par l'évaluation mensuelle, au cours de quatre années (1984, 1989, 1990, 1991), de caractéristiques morphophysiologiques et de la composition somatique chez deux espèces différant par leur régime alimentaire : la perche et le gardon. Les valeurs obtenues ont démontré qu'il y a certaines années (1984, 1989), en été, un ralentissement de la croissance pondérale, une diminution ou un arrêt de l'accrétion protéique accompagné d'une modification de la concentration d'acides aminés ainsi qu'une chute de la teneur en lipides somatiques. Ces résultats indiquent nettement l'existence, dans la retenue de Pareloup, de conditions nutritionnelles plus ou moins favorables aux populations pisciaires, durant la période estivale. Par ailleurs, la détermination de paramètres sanguins, au cours d'un cycle annuel (1992)(1993), chez plusieurs espèces de poissons (brème, chevesne, brochet, sandre, perche) a révélé que si la valeur de l'hématocrite, la cholestérolémie, la triglycéridémie et la protéinémie sont, d'une manière générale, relativement stables, la glycémie varierait avec la photopériode et le taux d'insuline circulante serait en relation avec le cycle sexuel, pour la plupart des espèces.Mots-clés. -Poissons, retenue, composition somatique, paramètres sanguins.Abstract. -The physiological state of fish was first assessed by monthly evaluation in four years (1 984, 1989, 1990, 1991) of certain morphophysiological characteristics and of somatic composition in two species (perch and roach) with different dietary habits. In 1984 and 1989, a slowing down in weight gain, a decrease or an interruption in protein accretion associated with changes in amino acid contents, and a fall in somatic lipid levels were observed in summer. These results clearly point to dietary conditions 258 F. Vellas et al.in Pareloup Reservoir which are more or less favorable to fish populations during this period. In addition, blood parameter rneasurernents, carried out frorn 1992 to 1993 in various fish species (bream, chub, pike, pike-perch, perch), generally showed relatively unchanged values for hematocrit and plasma cholesterol, triglyceride and protein contents, while plasma glucose levels appeared dependent on the photoperiod and circulating insulin rates on the reproductive cycle, for most species.
Les perturbations physiologiques potentiellement liées à la capture des poissons par filet maillant ou par épuisette ont été estimées chez des brochets, sandres, perches, brèmes, chevesnes, carpes et tanches de la retenue hydroélectrique de Pareloup (Aveyron). Toute capture provoque rapidement une hausse significative des taux de catecholamines (>10 ng.ml -1 ), Cortisol (> 100 ng.ml -1 ) et glucose (> 1 g.h 1 ) et une baisse des taux d'hormones thyroïdiennes (< 20 ng.ml -1 ) du plasma chez les sept espèces. Ces réponses physiologiques au stress de capture apparaissent significativement plus marquées suite à la pêche par filet maillant et ce, notamment, chez les espèces carnassières. D'après ces résultats, l'utilisation de filets maillants s'avère inadéquate pour des recherches à court terme sur la physiologie sanguine de populations naturelles de poissons, soulignant ainsi la nécessité après ce type de pêche d'une mise en place d'infrastructures particulières (e.g., viviers, cages flottantes, etc.) pour la phase ultérieure de récupération physiologique.Mots-clés : poisson, retenue, physiologie, stress de capture. PHYSIOLOGICAL RESPONSES OF SEVEN LACUSTRINE FISH SPECIES TO CAPTURE STRESS (GILL NET AND LANDING NET). ABSTRACTThe potential physiological disturbances experienced by fish as a result of capture with gill nets or landing nets were assessed in pike, pikeperch, perch, bream, chub, carp and tench from the hydroelectric reservoir of Pareloup (Aveyron). Capture of fish quickly resulted in both a significant elevation of plasma catecholamine (> 10 ng.ml" 1 ), Cortisol (> 100 ng.ml -1 ) and glucose (> 1 g.l -1 ) levels and a drop in plasma thyroid hormone levels (< 20 ng.ml -1 ) in all species. These physiological stress responses were found to be highly increased following gill-netting, especially in carnivorous species. Hence, these data suggest that the use of gill nets is rather inadequate for short-term researches on blood physiology of ferai fish populations, then attesting to the necessity of settling up experimental facilities (e.g., fish-ponds, floating coops, etc.) following gill-netting to ensure a complete recovery of fish from capture stress.
Résumé. -Lors de la vidange de la retenue de Pareloup, on pouvait supposer que la restriction de l'espace vital entraînerait des modifications de la biologie et de la physio¬ logie des poissons. Dans le but d'obtenir des données sur l'état «sanitaire» des popu¬ lations pisciaires, l'évolution de caractéristiques morphophysiologiques (facteur de condition, rapports gonado-et hépatosomatiques) et de quelques paramètres sanguins (hématocrite, glycémie, protéinémie, lipémie et insulinémie) a été suivie. Les campagnes de pêches se sont déroulées d'avril à juillet 1992 et lors de la vidange progressive de la retenue, d'avril à juin 1 993. Les prises de sang par ponction intracardiaque ont été effectuées dès la capture d'espèces carnivores (brochet, sandre, perche) et omnivores (brème, chevesne). De cette étude, il ressort que : les poissons, et en particulier le sandre, présentent une forte valeur de la glycémie consécutive au stress occasionné par la pêche aux filets, le comportement alimentaire des animaux au moment de la vidange est différent selon l'espèce considérée, mais la variabilité du volume de la retenue ne semble pas avoir d'incidence patho¬ logique majeure sur le métabolisme des poissons.Mots-clés. -Téléostéens, retenue, vidange, écophysiologie.Abstract. -At the time of draining of Pareloup reservoir, it was assumed that restriction of living space would lead to biological and physiological changes in fish. In order to obtain data on the state of health of fish populations, changes in physiological charac¬ teristics (condition factor, gonado-and hepatosomatic index) and in some blood para¬ meters (hematocrit, glucose, proteins, lipids and insulin) were monitored. Field experiments were conducted from April to July 1992, and during the gradual draining Hydroécol. Appl. (1994) les poissons, et en particulier le sandre, présentent une forte valeur de la glycémie consécutive au stress occasionné par la pêche aux filets, le comportement alimentaire des animaux au moment de la vidange est différent selon l'espèce considérée, mais la variabilité du volume de la retenue ne semble pas avoir d'incidence patho¬ logique majeure sur le métabolisme des poissons. Mots-clés. -Téléostéens, retenue, vidange, écophysiologie. Abstract. -At the time of draining of Pareloup reservoir, it was assumed that restriction of living space would lead to biological and physiological changes in fish. In order to obtain data on the state of health of fish populations, changes in physiological charac¬ teristics (condition factor, gonado-and hepatosomatic index) and in some blood para¬ meters (hematocrit, glucose, proteins, lipids and insulin) were monitored. Field experiments were conducted from April to July 1992, and during the gradual draining 294 F. Bau, J.P. Parent et F. Vellas of the reservoir from April to June 1993. Blood samples were taken by intracardiac puncture immediately following netting of carnivorous (pike, pikeperch, perch) and om¬ nivorous (bream, chub) species. The study indicated that: fish, in particular pikep...
D'importantes mortalités ont été notées après la phase d'acclimatation chez des populations de perches et gardons sauvages placées en stabulation. Une diminution de la dureté totale de l'eau de l'ordre de 40 mg/l de CaC0 3 semble être à l'origine de la mort des animaux. L'effet de cette baisse des concentrations en Ca 2 + et Mg 2+ de l'eau paraît être potentialisé par une modification thermique. De plus, ne pourrait-on pas observer dans ces conditions une forte modification des seuils de toxicité de certaines substances polluantes ?Unexplained cases of mortality in captive wild fish : possible synergy between hardness and temperature Keywords : wild fish, stabling, mortality, water hardness, temperature.High death rates were noted in wild perch and roach populations shortly after the stage of acclimatization in a tank. A decrease in water hardness by about 40 mg/l of CaC0 3 seemed to cause the mortalities. The effect of reduced ambient Ca 2+ and Mg 2+ levels may be promoted by a thermal modification. Furthermore, in these conditions, couldn't we observe a strong alteration in threshold concentrations of pollutants ?
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