(a) Total dissolved salt mass in the Vaccarès Lagoon System from 1999 to 2019, calculated as described in part 2.2.2. (b) Mean water level in the Vaccarès Lagoon System, which is the average value of the water levels measured at locations 12, 14, and 15 (see Figure 2). (c) Annual percentage of time with water level in the Vaccarès Lagoon System exceeding sea level (measured at location 13).

(a) Total dissolved salt mass in the Vaccarès Lagoon System from 1999 to 2019, calculated as described in part 2.2.2. (b) Mean water level in the Vaccarès Lagoon System, which is the average value of the water levels measured at locations 12, 14, and 15 (see Figure 2). (c) Annual percentage of time with water level in the Vaccarès Lagoon System exceeding sea level (measured at location 13).

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The Vaccarès Lagoon System, located in the central part of the Rhône Delta (France), is a complex shallow coastal lagoon, exposed to a typical Mediterranean climate and a specific hydrological regime affected by man-controlled exchanges with the sea and agricultural drainage channels. In this article, we report the results obtained by a series of m...

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... To give an order of magnitude, averages calculated from 2010 to 2020 indicate that all sluice gates are closed for about 147 days (40% of the year), up to two sluice gates are opened about 101 days (28%), and at least three sluice gates are opened for about 117 days (32%). A previous study measured the ''sea to lagoons'' daily average volume at about 39,000 m 3 day , and the ''lagoons to sea'' daily average volume at about 48,000 m 3 day for the 1999-2007 period (Boutron et al., 2021). A permanently opened gate is located west on the channel near the 13 sluice gates (Fig. 2) and give access to a fish pass, which was implemented in January 2004. ...
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Article
Anthropogenic barriers such as tidal gates impair animal migration and ecological continuity. For migratory fishes, barriers may alter or impeach both upstream and downstream migrations. Juveniles of European eels, namely glass eels, have to pass those barriers when migrating upstream, whereas they have limited swimming capacities and are dependent on several environmental variables. Hydrological conditions, which can be modified by barrier management, are critical for glass eels. Here, we investigated the links between hydrological conditions and barrier management and the recruitment of glass eels at a connection between the Mediterranean Sea and a lagoon. To do that, we modeled the recruitment of glass eels over ten seasons accounting for temporal variations and co-variable effects. We modeled three aspects of recruitment: presence, level, and composition. We found that monthly and inter-annual effects explained the main part of the variations in glass eel recruitment but accounting for environmental effects improved our models, with a positive effect of temperature, for instance. We associated low levels of catches and recruitment of rather old individuals to high water flow rates when water flows out of the lagoon. Those results call for further studies on how sluice gate management may improve glass eel recruitment and seem to indicate that local stakeholders should adjust the number of open gates depending on the water level on both sides of the barrier.
... This is mainly due to their shallow water depth and to their communication with the sea, which is usually limited to one or a few channels. Their exposition to wind and to rare but heavy rainfalls can also trigger rapid changes in environmental conditions in the lagoons (Boutron et al., 2021). Eel is present in >70% of the Mediterranean lagoons (Pérez-Ruzafa et al., 2011) and is among the most frequent and abundant fish species in these habitats with estimated biomass as high as 30 kg ha −1 (Amilhat et al., 2008). ...
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