Impacts of an irrigation and hydroelectric scheme in a stream with a high rate of diadromy (Guadeloupe, Lesser Antilles): Can downstream alterations affect upstream faunal assemblages?
Fièvet, Eric; Tito de Morais, Luis; Tito de Morais, Anne; Monti, Dominique; Tachet, Henri
published: May 23, 2001
ArtNo. ESP141015103010, Price: 29.00 €
In order to determine whether downstream alterations may affect upstream faunal assemblages in streams dominated by diadromous species we sampled decapods and fish by electrofishing before (1991-1992) and after (1994-1998) the completion of an irrigation and hydroelectric scheme on the Grand-Carbet River, a typical fast-flowing stream of Guadeloupe, Lesser Antilles. Water abstraction occurred at a low-head dam (i.e. valley dam) at 230 m a.s.l. We investigated three study sites downstream of the dam at 15, 100 and 200 metres a.s.l. (respectively Sites 1 to 3) and two sites upstream at 436 and 540 metres a.s.l. (respectively Sites 4 and 5). The completion of the irrigation and hydroelectric scheme reduced the proportions of large-bodied carnivorous fish and decapod species at both downstream altered and upstream unaltered sites. Inversely the proportions of the small-bodied species significantly increased. At downstream sites the faunal assemblages (guild structure and taxon diversity) were more impacted at Site 2 where water depth decreased most (- 25 cm) than at Site 3 where water depth was least changed (-10 cm). An intermediate response was recorded at Site 1. At upstream sites the faunal assemblages were more modified at Site 4, i.e. the site closest to the dam, than at Site 5, i.e. the highest site. Faunal changes were more or less marked among sites, probably in relation to the degree of physical changes at downstream sites, and to distances from the dam at upstream sites.