This research is associated to the LIFE MIGRATOEBRE project (www.migratoebre.eu), which aims to improve fish migration in the lower Ebre river, a Mediterranean river, mostly focused on Anguilla anguilla, Alosa fallax, Petromyzon marinus and Acipenser sturio conservation and recovery.
Migrating periods, main fish movements and preferential downstream routes (if they overcome a weir above, enter to irrigation channels or go to hydroelectric turbines) of the Ebre fish population (López et al., 2012) are unknown.
Following Le Pichon et al. (2015), in spring 2017, ceded by EABX R.U. of IRSTEA-Bordeaux, 47 VEMCO VR2W-69 kHz receivers (stacked to a concrete blocks of 500 kg; 15 months of battery life) were installed in a river stretch of 115 km long, between Flix dam and the Mediterranean Sea, including 4 Ebre delta coastal lagoons. Between May and October 2017, 30 fish from 58 km upstream the river mouth were marked: 5 A. fallax (using V9-2H acoustic pingers; 9x29 mm, introduced by the mouth, without anesthesia; 270 days of battery life), were released at the catching point; and 11 A. Anguilla, 13 M. cephalus, and 1 L. ramada (using V13 acoustic pingers; 13x36 mm, placed in the peritoneal cavity, with anesthesia and suture; 513 days of battery life), 52 km upstream (downstream Flix dam). An active tracking from a boat with a VR100 acoustic receiver and directional (VH110) hydrophone was also done.
A. fallax went soon to the sea. M. cephalus were detected 3 months later their release, in July and August, upstream and downstream Xerta weir. None fish did not go in or out the coastal lagoons 10 months later.
Obtained results seems indicate that the Ebre river possibly allows the recovery for those endangered species. To reinforce this information, other fish will be marked, including, if available, juveniles of A. sturio in 2019.