Ecological consequences of hydropower development in Central America: Impacts of small dams and water diversion on neotropical stream fish assemblages.
Abstract: Small dams for hydropower have caused widespread alteration of Central
American rivers, yet much of recent development has gone undocumented
by scientists and conservationists. We examined the ecological effects
of a small hydropower plant (Dona Julia Hydroelectric Center) on two
low-order streams (the Puerto Viejo River and Quebradon stream)
draining a mountainous area of Costa Rica. Operation of the Dona Julia
plant has dewatered these streams, reducing discharge to similar to 10%
of average annual flow. This study compared fish assemblage composition
and aquatic habitat upstream and downstream of diversion dams on two
streams and along a similar to 4 km dewatered reach of the Puerto Viejo
River in an attempt to evaluate current instream flow recommendations
for regulated Costa Rican streams. Our results indicated that fish
assemblages directly upstream and downstream of the dam on the third
order Puerto Viejo River were dissimilar, suggesting that the small dam
(< 15 in high) hindered movement of fishes. Along the similar to 4
kin dewatered reach of the Puerto Viejo River, species count increased
with downstream distance from the dam. However, estimated species
richness and overall fish abundance were not significantly correlated
with downstream distance from the dam. Our results suggested that
effects of stream dewatering may be most pronounced for a subset of
species with more complex reproductive requirements, classified as
equilibrium-type species based on their life-history. In the absence of
changes to current operations, we expect that fish assemblages in the
Puerto Viejo River will be increasingly dominated by
opportunistic-type, colonizing fish species. Operations of many other
small hydropower plants in Costa Rica and other parts of Central
America mirror those of Doha Julia; the methods and results of this
study may be applicable to some of those projects.
Anderson-Olivas, E. A., M. C. Freeman, and C. M. Pringle. 2006. Ecological consequences of hydropower development in Central America: Impacts of small dams and water diversion on neotropical stream fish assemblages. River Research and Applications 22:397-411.
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