Abstract ID: 106

Tropical stream fish assemblages: predictability of changes in an annual time scale.

The effects of seasonal inundation on the biology of fishes of floodplains in large Amazonian rivers are well studied. However, seasonal changes in small headwater streams are considered to have little effect on fish assemblages. In this study, we analyzed changes in fish assemblage composition and species abundances in small Amazonian forest streams throughout a complete seasonal cycle. We sampled fish with hand and seine nets in 31 streams, located at Reserva Ducke, Manaus, Brazil. Each stream was surveyed at the end of the 2005 dry season, at the beginning of the 2006 rainy season and at the beginning of the 2006 dry season. The number of species detected and the total number of individuals was higher in the dry seasons. The fish assemblage showed a strong seasonal tendency, not related to changes in physical structure of the streams or to physical-chemical characteristics of the water. Most species that showed large seasonal differences in abundance per stream are known to occupy temporary ponds during the rainy season, when the stream valley is periodically inundated, creating an adjacent pond-network to streams. Short-duration lateral migrations to these ponds may play an important role in the seasonal fish-assemblage dynamics in Amazonian headwater streams. Our results contrast with previous studies on small Amazonian streams, which found little seasonal change in fish assemblages, highlighting the importance of the abundance of common-species as an indicator of general fish assemblage structure in biological monitoring programs. The entire study, entitled “Seasonal variation in fish assemblage composition of small Amazonian forest streams: evidence for predictable changes.”, was accepted for publication in Freshwater Biology journal and will appear in one of its next issues.

Session:  Biodiversity - Permanent plot networks for inventory of biodiversity and carbon stocks: integrating taxonomic and ecosystem objectives.

Presentation Type:  Poster