Allis shad larvae and juvenile tolerance to oxythermic stress
2019
Baumann, Loic | Vega, Joanna | Philip, Joris | Polese, Fabien | Jatteau, Philippe | Bardonnet, Agnes | Acolas, Marie-Laure
Allis shad (Alosa alosa) populations have shown an important decline throughout thelast few decades, and it is assumed that the species’ distribution area has been restricted. In the Gironde-GaronneDordogne system (GGD, SW France), its decline leads to the adoption of a fishery moratorium in 2008. Despite this measure, locally no signs of recovery are observed. One hypothesis consists of the inefficiency of the recruitment process: young-of-the-year Allis shad are exposed to many pressures during their downstream migration, such as hypoxia. In the GGD system, hypoxic events are frequent in summertime (periods of several days with water O2 saturations under 30%). Those events are thought to become more severe andfrequent according to most climate change scenarios. Such low O2 availability could threaten young Allis shadby altering their migration success. If authors have suggested that 3-months old Allis shad show lower resistance to hypoxia at highertemperature, the abilities of younger development stages have never been studied. Here we meant to describe tolerance range of 10, 30, 60 and 90-days oldAllis shad to oxythermic stress by conducting behavioural analysis at an individual scale in decreasing water oxygen saturation conditions (from 100 to 30%), at four temperatures (18, 22, 26°C for 10, 30 days-old ; 22, 26, 28°C for 60, 90 days-old). By this study, we aimed to bring useful information on the importance of oxythermic conditions for Allis shad in both larvae reintroduction purposes and juvenile migration success
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