| Summary: | The thesis focuses on different aspects of management and ecology of commercially important fish species in Lake Annecy: an oligotrophic lake situated in Rhône-Alpes region of France. The main objectives of the study were to evaluate the growth of whitefish and Arctic char in Lake Annecy, study the trophic interactions in food web and to propose a trophic model of the lake using Ecopath with Ecosim (EwE) software using data collected mostly during the last 10 years from commercial and recreational fisheries monitoring. Lake Annecy is important for both recreational and commercial fisheries and is under continual obligatory monitoring for daily fish catches since 1986. About 20 volunteer anglers also provided additional data about their fish catches since 1992. The fisheries data from different sources were compared to test their relative quality. For measured length distributions in the commercial fishery and the estimated length distributions from angler’s catches filtered by selectivity curve, the congruence was very good. The CPUE calculated from both obligatory and volunteer angler data were also well correlated. The results showed that volunteer anglers catch data were reliable enough to be a cost-effective fisheries management technique. Growth of whitefish population of Lake Annecy was studied using fisheries data collected by recreational and commercial fisheries during last 20 years to evaluate any change. Scales of whitefish collected from recreational and commercial fish catch were used to determine age and to estimate back-calculated length and growth. Fish growth was found to be on decline during the last few years. The yearly annual mean zooplankton density was correlated to the growth increment of fish during their 2nd year. Whitefish growth was not found to be dependent on any change in mean temperature, total phosphorous concentration and year class strength of cohorts. The effectiveness, growth and dispersal after release of fingerlings of Arctic char stocked in 1997 and 2001 from different ...
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