Aquatic invasions: new record and first data on the biology of Gambusia holbrooki (Girard, 1859) (Pisces, Poeciliidae) in Argentina

Abstract

Fish of the genus Gambusia have a wide distribution and are part of the 100 most harmful invasive species in the world. In Argentina, there are records of Gambusia affinis Baird y Girard, 1854 and Gambusia holbrooki Girard, 1859. The presence of G. holbrooki has been reported in some regions of the country. However, there is no comprehensive information available regarding the biology and habitat of this fish. The aim of this study is to report a new locality for G. holbrooki in Argentina and to investigate various aspects of its biology and of the ecosystem where it was captured. The research was conducted at La Helvecia shallow lake (95 ha, 33º25'23''S, 62º54'02''W), representing the first record for the province of Córdoba. Four seasonal samplings were performed. The water exhibited elevated values of conductivity (9,685 μS cm-1) and pH (8.9), coupled with low transparency (36 cm). The maximum temperature reached 25.1ºC. The total length (TL) range of G. holbrooki was 20 to 50 mm, with a female-to- male ratio of 2.48:1. Pregnancy stage was observed from 25 mm TL and was most prevalent in spring. The standard length (StL)-TL ratio of the population was: TL (mm)= 3.47 + 1.06 StL (n=228; r2=0.96). Differences in body condition indices were observed between seasons of the year (p<0.001). Gambusia holbrooki exhibits a higher catch per unit effort as temperatures increase and submerged hydrophyte coverage becomes more extensive. The results obtained indicate the urgent need to reinforce management measures aimed at controlling the spread of Gambusia in the central region of Argentina.