Effects of Physical Habitat Degradation on the Stream Fish Assemblage Structure in a Pasture Region

Abstract

We compared the fish assemblage structure from streams with different intensities of physical habitat degradation and chemical water pollution by domestic sewage in southeastern Brazil. Eight streams (R1-R8) showing less disturbed or more disturbed conditions of chemical water quality and of physical habitat quality were selected. Cumulative abundance and biomass, combined in ABC plots, revealed (i) biomass curves above the abundance curves, represented by the streams R1-R2 (water and habitat less disturbed) and R5-R6 (water more disturbed and habitat less disturbed), and (ii) biomass curves below the abundance curves, represented by the streams R3-R4 (water less disturbed and habitat more disturbed) and R7-R8 (water and habitat more disturbed). The quantitative structure of the ichthyofauna showed significant correspondence with physical habitat condition but not with chemical water quality. The most significant species to cause the dissimilarity between less disturbed and more disturbed physical habitats was the exotic Poecilia reticulata. Such results indicate that in the focused region-with little influence of industrial pollution, noncritical domestic sewage discharge, and soil predominantly used for pasture-streams with high physical habitat integrity possess a differently structured ichthyofauna than streams with relatively low physical habitat integrity, reinforcing the importance of the physical habitat quality and riparian conservation along these water courses, warranting the conservation of these systems. Indeed, our results also reinforce the importance of including biotic descriptors, particularly of the ichthyo-fauna, in water-monitoring programs designed to reveal signs of human interference.

Structure and integrity of fish assemblages in streams associated to conservation units in Central Brazil

“…The misuse of land and the riparian vegetation deforestation contribute to a marked habitat quality loss in aquatic ecosystems, which leads the dominance of generalist fish species (Casatti et al, 2006a). Continuous physical and chemical alterations of natural conditions of streams caused by human activity support the establishment of exotic fish species.…”

“…Several studies point out the altitude and hydrological variables (i.e., depth, width, and water velocity) as the those that best describe the distribution patterns and assemblage structure of headwaters fishes of Central Brazil (Valério et al, 2007;Aquino, 2008;Súarez & Lima-Júnior, 2009). In addition to these, riparian vegetation characteristics and the combination of types of mesohabitats and substrates should be emphasized according to their importance documented in several studies (Jones et al, 1999;Casatti et al, 2006a;Ferreira & Casatti, 2006;Teresa & Romero, 2010). As an example of mesohabitat influences, Langeani et al (2005) compared the ichthyofauna between a riffle and a pool from a Tietê river tributary and concluded that the pool was the more diverse mesohabitat.…”

“…Water temperature, air temperature, dissolved oxygen (Winkler modified by Pomeroy & Kirschman, 1945), pH (Schott ® Handlab1), turbidity (Quimis ® ) and water conductivity (Analion ® C-702) were measured downstream of the stretches.The mesohabitats types were visually classified according to Rincón (1999) and the presence of substrate types (sand, silt, gravel, pebble, and litter) were described for each sample unit. The environment physical integrity was also determined visually, according to the Physical Habitat Index (PHI) proposed by Casatti et al (2006aCasatti et al ( , 2006b. In this index, nine items that describe the riparian conditions, stream characteristics (e.g., combinations of substrate types, micro and mesohabitats) and margins stability (e.g., erosion and siltation presence) are visually evaluated.…”

The fish community as an indicator of biotic integrity of the streams in the Sinos River basin, Brazil

“…Casatti et al (2006), Braga and Andrade (2005) and Goldstein and Meador (2004) also reported an increase in the number of species per stream order. This relationship of species richness and stream order is considered to be a result of the species area relationship (Angermeier and Schlosser, 1989).…”

Influence of environmental variables on stream fish fauna at multiple spatial scales

“…It is omnivorous, prefers low water flow, sand or clay bottom substrate, and is resistant to high temperatures (compared with many other Brazilian species) (Gomes et al, 2000). However, previous studies associating R. quelen with disturbed streams considered its response to physicochemical water oscillation instead of disturbed instream habitats (Casatti et al, 2006;Dias & TejerinaGarro, 2010). Although O. pintoi lacks characteristics adapted to persistence in degraded streams, Lemes & Garruti (2002) found high frequency of the species in such systems.…”