EFFECTS OF EXOTIC FISHES ON THE SOMATIC CONDITION OF THE ENDANGERED KILLIFISH FUNDULUS LIMA (TELEOSTEI: FUNDULIDAE) IN OASES OF BAJA CALIFORNIA SUR, MEXICO

We assessed the effects of the abundance and biomass of four exotic fishes (common carp, Cyprinus carpio; guppy, Poecilia reticulata; green swordtail, Xiphophorus hellerii; and redbelly tilapia, Tilapia cf. zillii) on the residual somatic condition (Kr) of endangered Baja California killifish (Fundulus lima) in two oasis systems of Baja California Sur, Mexico. We used multiple regressions to analyze relationships between Kr of the killifish and 21 ecological variables. Biomass of redbelly tilapia and common carp were variables that better explained variation in Kr among populations of killifish. In both drainages, redbelly tilapia was the dominant fish, which relegated smaller habitat units to the other coexisting species of fishes, increasing competition among them and decreasing Kr and abundance of the endemic killifish. We concluded that Kr for populations of killifish may be a good indicator of the competitive interactions with exotic fishes in drainages of Baja California peninsula and should be considered when such stocks are subject to recovery plans or any other management program.