Life-history traits of the invasive mosquitofish (Gambusia affinis Baird and Girard, 1853) in the central Yangtze River, China

The western mosquitofish (Gambusia affinis Baird and Girard, 1853), which is considered one of the 100 worst invasive species in the world, has been introduced to China. However, there is little information on the biological characteristics of mosquitofish in China. To better determine how this invasive species might impact China, the life-history traits of western mosquitofish were studied in the central Yangtze River from April 2012 to March 2013. A total of 962 mosquitofish specimens were collected. The size of females and males ranged from 12 to 44 mm and 12 to 29 mm, respectively, and the maximum ages of males and females were 0+ years and 1+ years, respectively. Both sexes grew allometrically (males: negative (b = 2.593); females positive (b = 3.253)). Females were numerically dominant with an overall female-to-male sex ratio of 1.65:1. Specifically, the female-to-male sex ratio was higher in summer (2:1) and autumn (3:1) and did not deviate from the theoretical value of 1:1 in winter and spring. The smallest pregnant female had a total length of 21 mm, and fecundity ranged from 4 to 65 eggs. Compared with the findings obtained in other studies, the western mosquitofish population in the central Yangtze River is characterized by faster growth, lower fecundity and shorter life span. These traits might enable the successful invasion of mosquitofish in the central Yangtze River.