PARENT SESSION
Oral Session #61: Aquatic Ecology: Fish - Communities and interactions. Presiding: J. Chick.
Thursday, August 9, 2001. 8:00 AM to 11:45 AM. Hall of Ideas F.
Seasonal and habitat influences on fish communities within the lower Yasuni River Basin, Eastern Ecuador.
Galacatos, Katerina1, Stewart, Donald1, Barriga, Ramiro2, 1 2
ABSTRACT- Lagoon, river and forest stream habitats were sampled during the rainy, dry and transitional seasons in the lowland region of the Yasuni National Reserve in the Ecuadorian Amazon. Sampling gear (gill nets and baited minnow traps) and sampling effort (twelve consecutive overnight sets) remained constant among habitats and seasons. We collected 196 species, increasing the current number of species for the Napo River Basin to approximately 563. The steady rate of species accumulation per sample suggests that the fish fauna is still under sampled. Lagoon, river and forest stream fish communities are highly diverse and variable, comprised of common species found within several habitats, of characteristic species found throughout the year, and of seasonal species found only within transitional, wet or dry seasons. During the dry season, lagoon and river habitats had the highest number of individuals and species, as fishes were concentrated in decreasing habitat area. During transitional seasons, stream habitats had the highest species richness and abundance. In addition, species collected included vital food fishes and seasonal migrants. Brachyplatystoma vaillantii, Hemisorubim platyrhynchos, Platynematichthys notatus, Platystomatichthys sturio, and Sorubim lima)were found during both transitional and dry seasons which suggests that within the lower Yasuni these species may begin migrating earlier than expected. These findings highlight the importance of seasonality for both adequately assessing aquatic diversity and for developing research and conservation programs encompassing whole river ecosystems.
KEY WORDS: community ecology, neotropical fish, Amazon, Yasuni River