Journal Article

Fish-Passage Facilities as Ecological Traps in Large Neotropical Rivers

AGOSTINHO, ANGELO ANTONIO, PELICICE, FERNANDO MAYER

2008

Overview

At present most of the large rivers of South America are impounded. Management plans historically have relied on the construction of fish passages, specifically ladders, to mitigate the impact of these waterway blockages on fisheries and biodiversity. Nevertheless, the design of these facilities is not ecologically sound and they are not monitored continually. Consequently, the real role of South American fish passages in fisheries and biodiversity management is unclear and the results of some studies suggest that ladders are problematic in fish conservation. We examined the characteristics and negative aspects of fish passages within a larger context and considered the notion that these facilities are ecological traps in some Brazilian impoundments. Four conditions are required to characterize a fish passage as an ecological trap: (1) attractive forces leading fish to ascend the passage; (2) unidirectional migratory movements (upstream); (3) the environment above the passage has poor conditions for fish recruitment (e.g., the absence of spawning grounds and nursery areas); and (4) the environment below the passage has a proper structure for recruitment. When these conditions exist individuals move to poor-quality habitats, fitness is reduced, and populations are threatened. To exemplify this situation we analyzed two case studies in the upper Paraná River basin, Brazil, in which the four conditions were met and migratory fish populations were declining. If passages work as ecological traps, regional fisheries will be in danger of collapse and conservation policies toward biodiversity will become more difficult and ineffective. The situation demands the closing of the passage in conjunction with alternative management actions to preserve system functionality, especially the conservation of critical habitats downstream and the restoration of damaged habitats in the region.

• Publisher: Blackwell Publishing Inc,Blackwell Publishing, Inc,Blackwell,Blackwell Publishing Ltd
• Subject: Agnatha. Pisces / América del Sur / Anadromous fishes / Animal, plant and microbial ecology / Animals / Applied ecology / Biodiversity / biodiversity conservation / Biological and medical sciences / Brazil / case studies / conservación de la biodiversidad / Conservation / Conservation biology / Conservation of Natural Resources / Conservation of Natural Resources - methods / Conservation, protection and management of environment and wildlife / dam / Dams / Ecosystem / Environmental management / Environmental policy / Environmental restoration / escalera para peces / Fish / Fish conservation / fish ladder / Fish ladders / Fish migration / Fish populations / Fish trapping / Fisheries / Fisheries management / fishery management / Fishes / Fishes - physiology / Freshwater ecology / Freshwater fishes / Fundamental and applied biological sciences. Psychology / Habitat conservation / Habitats / ladders / manejo de pesquerías / methods / migratory fish / Parks, reserves, wildlife conservation. Endangered species: population survey and restocking / peces migratorios / physiology / presa / Riparian ecology / River basins / Rivers / South America / Spawning / Spawning grounds / tropics / Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution / watersheds