Alteration of Fish Diversity Downstream from Petit-Saut Dam in French Guiana. Implication of Ecological Strategies of Fish Species

Abstract

Dams are expected to decrease fish diversity because they deeply alter downstream environment. However, such decline has not been consistently observed although profound modifications in the structure and/or composition of fish communities were generally recorded, and were linked to modifications of the downstream environment. In this work we analyze data from observations made before and almost 10 years after the completion of a hydroelectric dam in the neotropics. We monitored fish diversity below that dam and compared the taxonomic and functional structures of the samples between the pre-and post-dam periods. A significant decrease in species richness was evidenced. Taxonomic and trophic structures were significantly different between the two periods. Conversely, the functional structure of samples based on reproductive traits did not change significantly after the damming. Concerning feeding habits, a large increase in relative abundance of detritivores and a parallel decrease of fish species feeding on terrestrial food sources were observed in samples taken 6-9 years after closure of the dam as compared with samples taken before the dam.

Population and biological parameters of selected fish species from the middle Xingu River, Amazon Basin

“…Data from the Tucuruí reservoir indicate an overall loss of approximately 25% of the original complement of species due to the interruption of migration routes (Merona et al, 2010). Other examples include the Brokopondo reservoir on the Suriname River, where only 41 of the original 172 species survived the damming of the river (Mol et al, 2007), and the Sinnamary reservoir in French Guiana, where the pattern was similar to that recorded at Tucuruí (Mérona, 2002;Mérona et al, 2005). Of 67 fish species studied for the middle Xingu river 22 (33%) were categorised as migratory or perform movements of displacement and recolonisation of habitat.…”

Modelling Tools to Analyze and Assess the Ecological Impact of Hydropower Dams

“…In addition, dams can alter periphyton biomass [10], provoke changed phytoplankton densities [60] and cause algal blooms [61]. Moreover, hydropower dams affect the taxonomic and trophic structure of fish communities and can cause a reduction of fish species richness [62,63] and abundance [64,65].…”

“…As a result, the choices of input variables and derived ecological indicators need critical review and validation by local experts before being reliable for model development. Finally, an assessment of hydropower dams based on model simulations has to be carried out with great care because models cannot always separate the dam impact from other anthropogenic influences [63].…”

Influence of environmental variables and anthropogenic perturbations on stream fish assemblages, Upper Paraná River, Central Brazil

“…This situation is often related to modification of stream hydrology by reservoirs, but reservoirs did not significantly influence many of our sites and fish assemblage ordination results. Reservoirs are known to regulate water velocity and channel width downstream (Mérona et al, 2005), increase water residence time (Thomaz et al, 1997), increase downstream substrate size (Oliveira & Lacerda, 2004), and consequently alter biotic communities (Agostinho et al, 1992). This likely only occurred in sites with low water velocities and narrow channel such as Taquara I, Buraco and Sapé, each of which were located upstream of a reservoir.…”