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Saint-Pourçain-sur-Sioule, France

Dauphin G.J.R.,French National Institute for Agricultural Research | Dauphin G.J.R.,Northwest Atlantic Fisheries Center | Brugel C.,Onema | Hoffmann-Legrand M.,Logrami | Prevost E.,French National Institute for Agricultural Research
Ecology of Freshwater Fish

In salmonid species, such as Atlantic salmon (Salmo salar L.), the most frequent type of data set available related to adult escapements are redd counts. When collected over a broad spatio-temporal domain, redd counts data are of great interest for tracking the variation through time of the spatial distribution of the potential spawners. This is important for management purposes when the habitat quality is variable across river sections of a catchment or when the spatial distribution can vary depending on management actions or on environmental factors. However, long-term data sets are prone to changes in data collection methodology. In this article, we present a new hierarchical Bayesian modelling approach that allows both (i) to account for a change in the data collection procedure and (ii) to analyse the variation through time of the potential spawners' spatial distribution. The value of the proposed approach is demonstrated by its application to the Atlantic salmon redd counts data collected in Allier (France) catchment from 1977 to 2011. The Allier can be divided into three main sections according to management and habitat considerations, and an important change occurred in the redd data collection in 1997: counts by foot or by boat were replaced by counts from a helicopter. A significant effect of this change on methodology is detected: less redds counted when using the helicopter counts. However, its explicit consideration in the modelling makes little difference with regard to the estimates of potential spawner abundance and their associated uncertainty. © 2013 John Wiley & Sons A/S. Source

Baisez A.,Logrami | Bach J.-M.,Logrami | Leon C.,Logrami | Parouty T.,Logrami | And 3 more authors.
Endangered Species Research

During summer periods when water temperatures are high, Atlantic salmon Salmo salar are forced to halt their migration. This phenomenon was observed in our study in the River Allier in France. Between 200 and 1200 S. salar have come to spawn in the River Allier every year for the last 2 decades, but the population has suffered a severe decline. In 2009, 30 individuals were radio tracked; of these, 11 died during the summer period, while the other 19 resumed their migration in the fall. This mortality level was higher amongst the S. salar that arrived towards the end of the migration period, i.e. those individuals that tended to spend the summer in the lower, warmer stretch of the river. In view of the continuing rise in freshwater temperatures, measures are urgently needed to reduce the impact of increased temperatures on fish in the River Allier. This could be achieved by (1) promoting summer delays further upstream by making it easier for fish to pass through dams and (2) by protecting the spawning adults, particularly in the locations of summer halt. This study is consistent with a growing body of literature that suggests that climate change could have devastating effects on the upstream migration phase of anadromous salmonids. © Inter-Research 2011. Source

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