New additions and persistence of the introduced fishes of the upper San Antonio River, Bexar County, Texas

The fish fauna of the upper San Antonio River, Bexar County, Texas, includes tan introduced species (Astyanax mexicanus, Hypostomus sp., Poecilia reticulata, P. latipinna, Xiphophorus helleri, Belonesox belizanus, Cichlasoma cyanoguttatum. Oreochromis mossambicus, O. aurea anti Tilapia zilli). A recent sample from this environment contained nine: of the ten known introduced species, as well as two additional species (the vermiculated highfin catfish, Pterygoplichthys disjunctivus, and the Amazon molly, Poecilia formosa), that were, heretofore, not found from this location. The only fish known to have been introduced but not taken in this collection, was Belonesox belizanus, a species introduced in the early 1960s and not captured or observed for more than 30 years and believed to be: extirpated. The introduced fishes appear to be having a substantial impact upon the native fishes of this river. Introduced species made up 61% of the species, 17% of the individuals, and 62% of the biomass of the sample. It further appears that urban influences have had a major impact upon the conditions leading to the present fsh assemblage.