Ecological Traits of Non-Native Fundulus Grandis in the Pecos River: Implications for Impacts on Native Species

Authors: Kelbi Delaune-Trotter, Allison Pease

Year: 2018

Abstract

Non-native inland populations of Gulf Killifish, Fundulus grandis, potentially threaten native fishes in the Lower Pecos River. Recent studies of F. grandis in the Pecos have shown them to be highly piscivorous compared to coastal populations, consuming native species such as the imperiled Pecos Pupfish. Otherwise, little is known about the ecology of this species in inland systems and the potential effects on native fishes. In this study we examined reproductive characteristics, size, and age of F. grandis in the Pecos River, Texas. Fish were collected from the Pecos River near Iraan, Texas twice per month in the spring, summer, and fall. Preliminary results indicate that reproduction takes place approximately between March through August, with gonadosomatic index (GSI) of females peaking in March. This suggests that the Pecos population may have a different spawning period than that described for native F. grandis in Texas coastal habitats. However, timing of peak GSI measurements is similar to that of coastal populations. Fish collected from the Pecos ranged in size between 25.7- 143.3 (mm) total length (TL) for males and 32.3 - 148.8 (mm) TL for females. Size structure of the Pecos River population suggests that there is a higher proportion of larger individuals in the invaded system. The relatively large size and piscivorous nature of F. grandis along with the degradation of the mainstem of the Pecos River, are attributes hypothesized to promote replacement of native species by non-native invaders. Thus, this study provides a foundation for understanding the potential impacts of F. grandis in this invaded, inland system.