Female reproductive biology of an exotic suckermouth armored catfish (Loricariidae) in the San Marcos River, Hays Co., Texas, with observations on environmental triggers

Invasive populations of suckermouth catfishes (Loricariidae) are native to Central and South America, but have become established in US and Mexican waters since the 1950's and have been reported to have negative impacts on North American freshwater ecosystems. Two genera of loricariids have been reported from Texas waters (Hypostomus spp. and Pterygoplichthys spp.), both of which have become established in aquatic ecosystems where there are warm-water refugia, or suitable and seasonally stable temperatures. In an effort to better understand the invasive dynamics of these loricariids in novel ecosystems, aspects of their reproductive biology such as fecundity, seasonality of spawning activity, and spawning frequency of the individual fish were studied for Hypostomus cf. niceforoi living in the spring-fed San Marcos River, Texas. Fecundity was similar to Hypostomus spp. in the native range. There did not appear to be any synchronicity of spawning between individual fish within the invasive population, and there was a hint in the oocyte size-frequency data that some of the fish may be spawning multiple times per year. The timing of spawning activity in the novel range was seasonally inverted compared to the pattern typical of loricariids in the native range. The season of peak reproductive activity was also less distinct in the novel range than in the native range, and the period of reproductive quiescence was more seasonally compressed than in the native range. We provide data and supporting arguments suggesting that photoperiod is the primary proximate factor triggering the onset of reproductive quiescence, as well as a return to reproductive activity for these fish in both their native and novel ranges.