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Introduction: The purpose of this page is to provide easy access to present knowledge of the freshwater fishes of western Ecuador. Much remains to be learned about this fauna. There is little published on it and what exists is broadly scattered and often difficult to access. Our interests in the fish fauna of western Ecuador are diverse. Not only is the ecology and evolution of the fauna poorly understood (not to mention basic taxonomy), but the region is also under intense anthropomorphic pressure due to population growth, pollution, and continued modification of land for agriculture and forestry. Consequently, there is an urgency to study organisms in this region. In addition, the isolation of the fauna makes it quite unique. The fish communities that have evolved in this region occur no where else on Earth. Understanding how fish communities in western Ecuador function will provide broader insight into the evolution of neotropical fish faunas. In addition, the lower species diversity makes understanding ecological relationships and community structure a bit easier. The fish fauna of western Ecuador has also been exposed to changing environmental conditions caused by both natural geological events (like the rise of the Andes and the coastal mountain range) and human influences. Understanding how species and communities have responded can increase our understanding of how organisms respond to major environmental disturbances.
Origin and Evolution: The freshwater fishes of western Ecuador (west of the Andes) are separated from those of eastern Ecuador by the Andes mountains. Fish diversity in western Ecuador is much lower than in eastern Ecuador probably because the west is much drier and has fewer and smaller rivers (on the eastern side of Ecuador the rivers ultimately merge with the mighty Amazon). There are approximately 140 species of fishes regularly inhabiting freshwater lakes and streams in western Ecuador (Barriga, 1991), of which approximately 80 are from families that mostly occur in freshwater. These are almost certainly underestimates, however. The primary freshwater species are a remnant of the larger fauna inhabiting the rest of South America and were isolated when the Andes rose. Of the approximately 40 genera inhabiting the area, about two thirds have species on the eastern side of the Andes as well (Barriga, 1991), and most of the genera endemic to the western side of the Andes are obviously recently derived from genera inhabiting the eastern side (Eigenmann, 1921a). The common origin of the fish fauna east and west of the Andes in Ecuador is evidenced by the similarity at higher taxonomic ranks. Of the 40 genera of western fishes from primary freshwater families, 30 have representatives both in western and eastern Ecuador. The fish fauna of western Ecuador has been evolving independently for millions of years, however, and is quite distinct from all other South American fish faunas (including western Colombia). It was described by Eigenmann (1921b) as "old and highly specialized" and as an assemblage extends from just north of the Esmeraldas drainage to northern Peru. The fish fauna of western Colombia is very different from that of western Ecuador, and Eigenmann (1921b) indicated that the fish fauna of the Magdalena drainage in Colmbia, for example, is more distinct from that of western Ecuador than from the fauna on the eastern side of the Andes in Colombia. These two faunas thus appear to have distinct origins and independent evolutionary histories. The delimitation of the Ecuadorian and Colombian faunas appears to occur somewhere between the Mira and Esmeraldas basins (Eigenmann, 1921b).
The order Characiformes is the most diverse group of fishes in western Ecuador and the most diverse family within the order is the Characidae (tetras). The order is also quite diverse ecologically and members range from small "minnow" type fish, to herbivores and detritivores, to large fish predators like Hoplias, the tahira or guanchiche. The order Siluriformes if the second most diverse group and the family Loricariidae (suckermouth catfishes) is the most diverse family within that order. Other important freshwater groups include the Cichlidae with the genera Andinoacara, Cichlasoma, and the non-native African tilapia, the order Gymnotiformes (electric fishes), the eleotridae (sleepers), the order Cyprinodontiformes, and the order Synbranchiformes. Fishes that are primarily marine or estuarine and occassionally enter freshwater are quite diverse and includes sciaenids, centropomids, gobiids, pleuronectiformes, gerreids, tetraodontids, clupeids, engraulids, etc. (Barriga, 1991). In all, there are approximately 50 species that come from families that are primarily marine or estuarine but occur frequently in freshwaters of western Ecuador. There are also a fair number of non-indigenous species, especially salmonids (at upper elevations) and tilapia, that are well established. Even a western Atlantic sciaenid, Sciaenops ocellatus (introduced for fish farming in the late 80's-90's) was reported several years ago (Bearez, pers. comm.) although its present status is unknown.
Guayas River Species List by Enrique Laaz and Antonio Torres: How to cite the web site: Aguirre, W.E., P. Calle, P. Jimenez-Prado, E. Laaz-Moncayo, R. Navarrete-Amaya, F. Nugra-Salazar, V.R. Shervette, and A. Torres-Noboa. 2017. The freshwater fishes of western Ecuador. World Wide Web publication retrieved from: http://condor.depaul.edu/waguirre/fishwestec/. Accessed: Month Day, Year. How to cite a particular species profile: Page Author. Year. Species name, Species profile published in Aguirre, W.E., P. Calle, P. Jimenez-Prado, E. Laaz-Moncayo, R. Navarrete-Amaya, F. Nugra-Salazar, V.R. Shervette, and A. Torres-Noboa. The freshwater fishes of western Ecuador. World Wide Web publication retrieved from: URL. Accessed: Month Day, Year. For example: Aguirre, W.E. 2017. Saccodon wagneri, Species profile published in Aguirre, W.E., P. Calle, P. Jimenez-Prado, E. Laaz-Moncayo, R. Navarrete-Amaya, F. Nugra-Salazar, V.R. Shervette, and A. Torres-Noboa. The freshwater fishes of western Ecuador. World Wide Web publication retrieved from: http://condor.depaul.edu/waguirre/fishwestec/saccodon_wagneri.html. Accessed: August 9, 2017. Acknowledgements: Our research has benefited from support by the Colleges of Science and Health and Liberal Arts and Social Sciences at DePaul University, the W. Burghardt Turner Fellowship Program, the Alliance for Graduate Education and the Professoriate (AGEP), the Long Island Group Advancing Science Education (LIGASE), the Department of Ecology and Evolution at Stony Brook University, and the Howard Hughes Medical Institute. Mireya Pozo and Mario Brito from Ecuador's Ministry of the Environment have been of great assistance with permits for field research conducted in Ecuador. Miguel Rojas edited many of the fish pictures on this web site. Jon Armbruster provided assistance with identification of some of the loricariids listed. Nathan Lujan allowed use of some of his pictures. We are grateful to the Field Museum of Natural History for allowing the use of pictures of some of their specimens on this website and Kevin Swagel for his help during our visits. Photo Credits Left: composite image created from figures in Eigenmann (1922). Right: picture of fisherman on the River Guayas taken by Windsor Aguirre. Created and Maintained by Windsor Aguirre Created August 26, 2006 |
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