Beyond just a dam blockage problem: larger artificial reservoirs are additional obstacles to reproductive fish migration in the Neotropics
Reservoirs formed by dams can hinder fish migration beyond physical barriers. Translocated Prochilodus showed reduced movement, disorientation, and limited ranges. Larger reservoirs further impair navigation, suggesting fish passage systems may fail if migrants cannot complete reproduction in altered environments.
Subject Tags
- Watersheds
- Biodiversity offsetting
- Fisheries
Abstract
One of the most conspicuous impacts of dam construction on fish is the blocking of their migratory routes. However, the formation of the reservoir, a lentic environment with distinct hydrological and ecological characteristics, can also constitute an obstacle to migration. This impact, however, is poorly explored in the scientific literature. Therefore, this study aimed to assess the movements of Prochilodus argenteus tagged with radio telemetry transmitters and manually translocated across the Três Marias Dam in the São Francisco River. The Três Marias reservoir covers an area of 1090 km2 and ranks among the largest artificial reservoirs in Brazil. Individuals translocated to the Três Marias reservoir showed reduced movement rates and home ranges. They appeared disoriented in the new environment, with many of them settling near fish farms and remaining there throughout the study period. A comparative analysis with existing literature on Neotropical species’ reproductive migration through artificial reservoirs revealed a trend: the ability of migratory fish to navigate reservoirs diminishes with their area, especially those exceeding 50 km2 or with a residence time surpassing 30 days. These results indicate that caution is needed when designing fish passage facilities for dams that form larger artificial reservoirs in the Neotropics. Even if these facilities are efficient in attracting and translocating migratory species, behavioral and physiological thresholds may prevent them from reaching suitable areas to complete their reproductive cycle in the new environment formed.
Citation
Lopes, J.D.M., Alves, C.B.M., Silva, F.D.O. and Pompeu, P.S., 2024. Beyond just a dam blockage problem: larger artificial reservoirs are additional obstacles to reproductive fish migration in the Neotropics. Environmental Biology of Fishes, 107(2), pp.217-229. https://doi.org/10.1007/s10641-024-01526-1
TNC Authors
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Fernanda de Oliveira Silva
Amazon Freshwater Fisheries Conservation Scientist
The Nature Conservancy
Email: f.silva@tnc.org