Abstract
In this study the fish assemblages of the silted Aguas Claras stream (AC) was compared with that of a reference, the São Carlos stream (SC), so as to identify potential fish indicators of integrity or degradation. Both streams, located about 5 km from one another, are part of the Upper Paraná river basin, Brazil, and present similar physiographical features. Twenty-one species were collected in AC (1,271 specimens) and 18 in SC (940 specimens). In AC, dominant species e.g., Corydoras aeneus (sandy pools), Serrapinnus notomelas, and Pyrrhulina australis (warm marginal shallow pools) were those favored by new microhabitats linked to siltation and removal of the riparian vegetation. Changes in the composition of the marginal vegetation resulted in dominance of species such as Hisonotus francirochai (marginal grasses). In SC the dominant species was Phalloceros caudimacultus, abundant in marginal shallow pools, and Trichomycterus diabolus. and Hypostomus nigromaculatus, exclusively riffle-dwelling species, which were absent in AC. Fish assemblage monitoring is recommended for use in riparian management programs in order to evaluate negative instream sedimentation effects.
Highlights
Among several consequences of streamside vegetation removal, siltation is one that most directly affects warmwater fish assemblages (Rabeni & Smale, 1995)
Input effects on fish assemblages as ecological indicators are poorly documented in the literature
According to Rabeni & Smale (1995), fish responses to siltation are more evident at the assemblage level and, in both interregional or intraregional comparisons, herbivores, benthic invertivores, and lithophilous spawners are reliable indicators of siltation
Summary
Among several consequences of streamside vegetation removal, siltation is one that most directly affects warmwater fish assemblages (Rabeni & Smale, 1995). A variety of mechanisms by which siltation affects fishes have been described, including physiological stress from clogged gills, egg and larvae smothering, changes in normal feeding, and other activities that depend on vision (Rabeni & Smale, 1995). To better assess the loss of aquatic biological diversity and integrity, biological indices have been drafted to assess water quality programs worldwide (Karr, 1981; Hughes & Oberdorff, 1999). Appropriate applications of such indices require knowledge of many biological and ecological attributes of fish assemblages
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