The basin holds 105 permanent streams and rivers that number , the region being drenched in rains regularly. The Navarrese side of the basin (rural landscape) is inhabited by 22,000 inhabitants. 70% of its population have the sewage treated before spilling to the river. But for the first 15-odd kilometres, the river clings to the north to south disposition of other neighbouring rivers of Gipuzkoa joining the Bay of Biscay, e.g. Urumea, Oria, etc. Strengthened by the waters harvested from the sides of the pass of Belate, downstream of Doneztebe the river heads north and crosses the town of Bera at the north end of Navarre before entering Gipuzkoa at Endarlatsa. From the town of Doneztebe on, the main road N-121 runs along till the roundabout across the river from the toll of Biriatu by the AP-8 (motorway). Next comes the quarter Behobia and the major towns on the shores of the estuary. The main tributaries of the Bidasoa are the minor rivers Zeberia (length ), Ezkurra (), Latsa () and Endara (). Additionally, further small rivers and streams feed the Bidasoa all along. Fishing and environmental challenges The Navarrese tract of the river is a preferred destination for fishing enthusiasts, the river being home to several native fish species, namely eel (Anguilla anguilla), salmon (Salmo palar), trout (Salmo trutta), bullhead (Cottus gobio), Barbatula barbatula, Phoxinus phoxinus, gudgeon (Gobio lozanoi), sea lamprey (Petromyzon marinus), allis shad (Alosa alosa), flounder (Platichthys flesus) and grey mullet (Chelon labrosus), some of them declared endangered species and highly interesting (especially bullhead and salmon). Moreover, a species of the Ebro, Chondrostoma miegii, has been introduced in the last 30–40 years on the lower tract of the Bidasoa, thereafter extending gradually upstream. As a result, overfishing has become a major problem for the river's fauna, with special pressure put on salmon migrating upstream to spawn. They do not make it to their goal and die before spawning, either falling prey to fishers' bait or an inability to overcome hydroelectric power stations (128 over all the course) and the 114 related dams, since 63% of them prevent migratory fish from achieving their purpose. Schemes by the Regional Government of Navarre are underway with a view to handling the issue. See also List of rivers of Spain Battle of the Bidassoa (1813) Bidasoa-Txingudi Pheasant Island (Île des Faisans) Footnotes References Report on the Environmental State of the Bidasoa