Bresle River Long Term Observatory

Monitoring of migratory fish populations (salmon, lamprey, eel, etc.) is based on a dual trapping system. The fish are intercepted as they leave or enter the river following their marine life stage.

The monitoring station consists of two complementary facilities, located respectively at Eu (76), 3 km from the sea, and at Beauchamps (80), 15 km from the sea; these enable, through the use of mark-recapture methods, a quantitative assessment of the upstream and downstream of the river. Fish trapping activities take place throughout the year.

Trapping

Quantitative assessments of the upstream and downstream migration of salmon and sea trout are carried out annually using a capture-mark-recapture protocol.

•  Trapping of adult upstream-migrating salmon and sea trout:

                      a) main trap (P1), for capturing and tagging upstream-migrating individuals, at Eu.

                      b) secondary trap (P2), for recapture and monitoring of individuals returning to the sea after spawning, at Beauchamps.

• Trapping of downstream-migrating juvenile salmon and sea trout:

                      a)  main trap (P1), for capture and tagging, at Beauchamps.

                       b) secondary trap (P2), for recapture and monitoring, at Eu.

Meanwhile eels, are monitored at the juvenile stage (colonizing migration into the river) at Eu; downstream-migrating adults (spawning migration) are captured at Beauchamps (P1) and then at Eu (P2). Tagging and recapture surveys, aimed at assessing inflow rates, were carried out between 2008 and 2010; however, the data collected so far is insufficient to estimate these rates.

	Salmon Monitoring of salmon populations since 1982	See report
	Trout Monitoring of trout populations since 1982	See report
	Eels Monitoring of eels populations since 1982	See report