Structure of Fish Assemblages in Amazonian Rain-Forest Streams: Effects of Habitats and Locality
We examined fish assemblage structure in three headwater rain-forest streams in the Urubu River Basin, Central Amazonia, as it relates to habitat heterogeneity. Riffles and pools, two types of stream habitat, were defined by current, depth, and substrate parameters, adjusted for Amazonian stream characteristics. We assessed species richness, composition, and abundance as they varied between riffles and pools across three similar streams. Four riffles and four pools were identified in each stream and sampled four times during 1996 and 1997. The samples yielded a total of 856 individuals of 22 species. The most abundant species were in the families Characidae, Lebiasinidae, Helogenidae, and Rivulidae. We found an interactive influence of riffle/pool habitat and stream factors on species richness, composition, and abundance. Rain-forest stream fish assemblages are structured by both habitat and stream locality.Abstract
Species richness in riffle and pool habitats in three streams: Igarapé 41 (Q); Igarapé Gavião (G); and Igarapé Porto Alegre (P). Rectangles encompass standard errors and error bars standard deviation.
Abundance of (A) Pyrrhulina brevis, (B) Rivulus compressus, (C) Hemigrammus sp., (D) Hyphessobrycon cf. heterorhabdus, (E) Nannostomus marginatus, (F) Iguanodectes variatus, and (G) Helogenes marmoratus, in riffles and pools in streams Igarapé 41 (Q), Igarapé Gavião (G) and Igarapé Porto Alegre (P). Rectangles encompass standard errors, and error bars standard deviation.
Abundance of Hyphessobrycon cf. melazonatus in riffles and pools of streams Igarapé 41(Q) and Igarapé Gavião(G) in the four sampling periods (P1–P4). Rectangles encompass standard errors, and error bars standard deviation.