Is fish passage technology saving fish resources in the lower la plata river basin?. Internacional Symposium on Fish Pasajes in South America

NORBERTO OLDANI; CLAUDIO R.M. BAIGÚN; JOHN NESTLER; A. GOODWIN

Neotropical Ichthyology

Año: 2006

Dam building has experienced considerable growth in South America in the last 40 years. In the upper Parana basin in Brazil, 452 dams have been constructed being river regulation considered as one of the primary factors reducing fish diversity and migratory species depletion. In contrast in the lower La Plata River basin only two large dams have been constructed. At present there is large concern about impact of regulated river of such species which constitute the basis of recreational and commercial fisheries in the basin. This paper focuses on the fish passage system performance at Yacyreta and Salto Dams showing that fish passage systems failed to transfer upstream massive amounts of migratory species. Yacyreta Dam has two functioning elevators with important design problems.  As a result, fish passage efficiency of target species is lower than 2 %. Diversity of transferred species appeared as low since 85 % of dominant species at the elevators were represented by a catfish species (Pimelodus maculatus) and two Doradidae species (Oxydoras kneri and Rhinodoras d’orbygni). In turn large migratory species rarely surpassed 5 % In turn Salto Grande Dam two Borland locks were installed which performance varied considerably depending upon operation of the powerhouse and spillway and tailrace elevations. Most of passed species belong to a small catfish species (Parapimelodus valenciennesi) and a clupeid species (Lycengraulis grossidens). New directions for fish passage design are required to preserve migratory species in South American regulated rivers.  Integrated information from geomorphology (habitat), hydrodynamic cues used by fish to select upstream and downstream migration swim paths, fish swimming capabilities, and detailed population studies is needed.