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Biologie de la perche (Perca fluviatilis) dans le réservoir du Mirgenbach (Cattenom, Moselle)

Abstract : The Mirgenbach reservoir created by pumping water from the river Moselle in 1985 is a safety reservoiir and a buffer zone for the Cattenom nuclear power plant (Moselle, north-east France). With its maximum depth of 20 meters, this reservoir is characterized by its heated waters and the absence of a thermo-stratification. It is an ecological study of this lake-reservoir which contributes to the knowledge of the fish population and the demography of an initially dominant species : the perch, perca fluviatilis. From 1987 to 1991, various fishing techniques were employed on the Mirgenbach lake-reservoir. Two kinds of gill nets were used : traditional nets and vertical nets which took samples from the water surface to the bottom. A set of vertical nets were immersed in stations during fishing sessions spread along the year. Among the various fishing gears used, vertical gill nets turned out to the best sampling device for the analysis of the perch demography. The analysis of catches thanks to these various fishing gears enabled us to know its location and its evolution in the lake-reservoir. All in all, 18 fish species were identified with a majority of perch (perc fluviatilis), roach (rutilus rutilus) and common bream (abramis brama). The multiple correspondence analysis led us to distinguish several groups of stations, each having its own species. The sampled fish with traditional and vertical gill nets as well as angling enabled us to know the selectivity of each device and to study the demographic structure evolution. The number of catches has decreased dramatically within this period. The seasonal repartition of the species in the reservoir was studied is an annual cycle with vertical gill nets. The best catches of this carnivorous fish were made in summer, except in a littoral station close to a spawning area before reproduction time. The vertical distribution of this species according to bathymetry. The perches were found mostly at the bottom of the stations closest to the shore and from the bottom to the surface in the pelagic stations. The reproductive study of the perch is based upon weight index and the maturity stage index. Age is identified by the application of scalimetrie and operculometrie methods. The two corresponding structures can be used equally to describe the perch growth. In the Mirgenbach reservoir, the reproduction of the perch takes place from mid-march to mid-april. Perch may spawn since the end of february. Spawning period takes place precociously one month earlier than in other ponds of the region Lorraine. Males are mature at one year old and females at two years, with an intermediate fecundity for almost fish. In comparison with others lakes, the perch growth is faster in the Mirgenbach reservoir : it reaches 12 cm at one year. This growth speed depends upon the very good thermal conditions and a better availability of food resources with the decreasing of its population. Digestive contents are analysed to study the diet of perch. Perca fluviatilis fed on Crustacean with a selective predation on the cladocera Daphnia longispina, insects mostly chironomes larvae and nymphes, molluscs gasteropodes and fish such as roach (rutilus rutilus), ruffe (gymnocephalus cernua). Cannibalism occurs within perch in the reservoir. Nevertheless, diet depends upon sex and perch length and also seasons. A bibliographic review and a discussion on this Mirgenbach reservoir enables us to compare our results to others
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Anne Flesch. Biologie de la perche (Perca fluviatilis) dans le réservoir du Mirgenbach (Cattenom, Moselle). Biologie animale. Université Paul Verlaine - Metz, 1994. Français. ⟨NNT : 1994METZ054S⟩. ⟨tel-01776808⟩

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