Conservation and management of migratory fauna and dams in tropical streams of Puerto Rico



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1. Compared to most other tropical regions, Puerto Rico appears to have dammed its running waters decades earlier and to a greater degree. The island has more large dams per unit area than many countries in both tropical and temperate regions (e.g., 3x that of the U.S.), and the peak rate of large dam construction occurred two and three decades prior to reported peak rates in Latin America, Asia and Africa.

2. Puerto Rico is a potential window into the future of freshwater migratory fauna in tropical regions, given the island's extent and magnitude of dam development and the available scientific information on ecology and management of the island's migratory fauna.

3. We review ecology, management and conservation of migratory fauna in relation to dams in Puerto Rico. Our review includes a synthesis of recent and unpublished observations on upstream effects of large dams on migratory fauna and an analysis of patterns in free crest spillway discharge across Puerto Rican reservoirs. Analyses suggest that large dams with rare spillway discharge cause near, not complete, extirpation of upstream populations of migratory fauna. They also suggest several management and conservation issues in need of further research and consideration. These include research on the costs, benefits and effectiveness of simple fish/shrimp passage designs involving simulating spillway discharge and the appropriateness of establishing predatory fishes in reservoirs of historically fishless drainages.

Date Range: 
1993-06-22 00:00:00 to 2003-06-30 00:00:00



Additional Project roles: 

Name: Miguel C Leon Role: Data Manager
Name: Catherine Pringle Role: Associated Researcher
Name: William H. McDowell Role: Associated Researcher


Spillway discharge analysis: For each large dam downstream from our high-gradient, high-elevation sampling sites from Greathouse et al. (in press) (dams were: Dos Bocas, Caonillas, Matrullas, Carite, Toa Vaca, Luchetti, Garzas), we obtained the entire USGS daily-lake-elevation record prior to the last date of our field research on 30 June 2003 (records ranged from 4-15 years long). For other dams, we analyzed water years 1999 and 2000 (for dams: Guayabal, Patillas, Guajataca, Cidra, Loco, Loi­za, Guayo, La Plata, Cerrillos) or records from recently-installed lake elevation gages (installations in November 2004: Comerio; installations in February 2005: Coamo, Adjuntas, Vaca, Prieto, Yahuecas). For each record, we then determined the percentage of days with spillway discharge (100 times the number of days with lake elevations exceeding the spillway crest elevation divided by the total number of days for which a lake elevation was reported). Previously unpublished observations of native shrimps and fishes occurring upstream from large dams were made by various methods ranging from simple visual observation to non-quantitative sampling to quantitative sampling by electroshocking. Descriptions of the methods, when available, are included in the data set file (aquaticconservation.txt).



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