Ecological guilds of fishes in streams of an arid subtropical drainage in western Mexico.

Knowledge of ecological guilds of river fish communities can be useful for stream conservation and management. We determined trophic and ecological guilds for 17 fish species in three rivers of the Balsas basin, western Mexico: Cupatitzio, La Parota, and El Marques. First, for the nine most common species, we analyzed diet content information, niche breadth, and overlap. We relied on published literature for the eight least common species. The food resources used by all these fishes were mostly insects and detritus. Most species were deemed generalists with a significant overlap among carnivorous species. There were three trophic guilds: insectivores, detritivore-herbivores, and omnivores. Second, 14 ecological guilds were defined, combining the trophic groupings with direct observations on size and position in the water column, as well as information from the literature on reproductive mode. The most frequent ecological guild was viviparous/ mid-sized/detritivorous/mid-water, which was present at all sampled sites, followed by the viviparous/small/detritivorous/surface guild, present in 9 out of 10 sites. Four guilds were exclusive to the depositional section of the system: oviparous-complex (i.e., nest builders or with parental care)/large-bodied/detritivorous-herbivorous/benthic, oviparous-complex/mid-sized/ omnivorous/mid-water, oviparous-simple/small/insectivorous/mid-water, and viviparous/small/omnivorous/mid-water. No guild was exclusive to the erosive section of the rivers. In spite of using similar resources, the conformation of ecological guilds suggests segregation, both by distribution and by differential use of the habitat, facilitating the coexistence of species in the fish community of this basin. [ABSTRACT FROM AUTHOR]