A new study of the Yasuni National Reserve in the Ecuadorian Amazon has increased the number of fish species known in the area to around 562.
Galacatos, Barriga-Salazar and Stewart from Escuela Politcnica Nacional in Ecuador, and the State University of New York, studied a wide range of habitats from lagoons and rivers to forest streams during the course of a year. They have just published their findings in the journal Environmental Biology of Fishes.
The team collected a total of 195 different fish species during the dry and wet seasons, and say that the steady rate at which they were finding new ones suggests that there are still many more left to find in the Napo River basin area they sampled.
The study also allowed them to compare the different fish assemblages that live in different Amazonian habitats.
Forest streams, for example, were found to be characterised by a number of species including the tetra Hyphessobrycon copelandi, the knifefish Sternopyugus macrurus, an undescribed Pimelodella sp., and the predatory characin Hoplias malabaricus.
Lagoons were characterised mainly by curimatids, including Psectrogaster amazonica, Curimata vittata, Potamorhina altamazonica, Cyphocharax plumbeus and P. latior, while rivers were characterised by the characins Hyphessobrycon copelandi and Hemigrammus cf. lunatus and the catfishes Nemadoras humeralis, Pimelodella sp. C and Sorubim sp. A.
Since the dry season results in many of the habitats getting much smaller, the dry season was the time when both the abundance and diversity of fish caught was greatest.
Streams and other habitats gave different results, say the researchers: "Stream habitats had the highest species richness and abundance during the rising water and falling water seasons. Species collected included vital food fishes and seasonal migrants.
"The migratory catfishes Brachyplatystoma vaillantii, Hemisorubim platyrhynchos, Platynematichthys notatus, Platystomatichthys sturio and Sorubim lima were collected during the falling water season, which suggests that these species may begin migrating earlier than expected. These findings highlight the importance of seasonality for both adequately assessing aquatic biodiversity and for developing research and conservation programs encompassing whole river ecosystems."
For more details see the full paper: K. Galacatos, R. Barriga-Salazar and D.J. Stewart (2004) - Seasonal and Habitat Influences on Fish Communities within the Lower Yasuni River Basin of the Ecuadorian Amazon. Environmental Biology of Fishes. 71 (1): 33-51, September 2004.