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24, chemin de Borde Rouge –Auzeville – CS52627
31326 Castanet Tolosan CEDEX - France

Dernière mise à jour : Mai 2018

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The Oir, Scorff and Bresle river monitoring sites

The Oir, Scorff and Bresle are three rivers that have been monitored by INRAE and the French biodiversity agency OFB for over 30 years. The U3E unit is tasked with managing the monitoring sites. They were initially chosen solely for monitoring migratory salmonids, but have gradually been equipped with instruments for monitoring trends in amphihaline fish communities under the impact of local and global environmental change.

Each site is equipped with a migratory fish monitoring station with upstream and downstream traps. The sites' design, the facilities (field laboratory, workshop etc.) and the various instruments spread around the stream networks enable the study of different biotic and abiotic compartments throughout their catchments. These rivers have now been monitored in detail for over 35 years, producing extensive chronological data series.

The Oir, Scorff and Bresle rivers, along with the Nivelle, which is monitored by the Ecobiop research unit at Saint-Pée-sur-Nivelle, are used for the work of ORE DiaPFC (monitoring unit for diadromous fish in coastal rivers) and the OFB/INRAE research hub Gest'Aqua (management of aquatic ecosystems in farming areas).

These four rivers are listed as Index Rivers by ICES, the International Council for the Exploration of the Sea, which is tasked with making recommendations for the international management of fish stocks.

Oir capture site

The Oir site

Length: 21 km
Catchment: 86 km2

The Oir is a tributary of the Sélune, which drains into the bay of Mont Saint-Michel. The upstream reaches of the Sélune are inaccessible to migratory fish because their way is blocked by an impassable dam 15 km from the sea. The fish can only spawn in two tributaries downstream of the dam, the Beuvron and the Oir. The Oir is the more productive of the two spawning grounds.

Runs of fish migrating up- and downstream are monitored by means of traps at the Moulin de Cerisel station.
A former fish farm next to the station is used for stocking experimental animals.

Scorff - Moulin des princes capture site

The Scorff site

Length: 70 km
Catchment: 480 km²

The Scorff is a small river that drains into the Atlantic in Lorient harbour in Brittany. The fish monitoring station is on the lower part of the main river, at the tidal limit, just at the start of the estuary. This means that fish trapping and related work continues all year round. Species trapped include salmon, shad and lamprey.

The monitoring station at Pont-Scorff is open to the public, with a purpose-designed visitor reception space.

La Bresle river

The Bresle site

Length: 72 km
Catchment: 748 km²

The Bresle is a coastal river in Normandy whose headwaters are in the Seine-Maritime département and which drains into the Channel at Trépot.

To monitor migratory fish, traps are placed to intercept them on their way seawards, or going back up the river after their sea-dwelling stage. The monitoring station comprises two complementary trapping sites, one at Eu (in Seine-Maritime), 3 km from the sea, and one at Beauchamps, in the Somme département, 15 km from the sea. Fish trapping (of salmon, lamprey, eel etc.) and related work goes on all year round.