Life History Traits of the Chinese Minnow ＂Rhynchocypris Oxycephalus＂ in the Upper Branch of Yangtze River, China

Background Study of the life history traits of any species plays an essential role for understanding their relationship with the surrounding environment and scientific management. The Chinese minnow Rhynchocypris oxycephalus , an ecologically and economically important species which was widely distributed in East Asia, is currently diminishing. In the present study, we depicted the main life history traits of R. oxycephalus for the first time. Results A total of 442 individuals were collected from April 2012 to March 2013, with total length (TL) ranging from 32.2 to 158.0 mm. The otolith (lapillus) was proved suitable for age determination. Moreover, the results from marginal increment ratio (MIR) analyses demonstrated its unusual growth pattern: two pairs of opaque and transparent bands were formed each year, which might provide some implications for the age determination of other species. The maximum age for females (4 years) was higher than for males (3 years), while 1- and 2-year-old individuals dominated the population. Both females and males reached maturity at 1 year, and the TL at first maturity was 78.8 mm for females and 60.3 mm for males. Obvious sexual dimorphism was observed as females growing faster and larger than males after maturity. As a multiple spawner, R. oxycephalus releases batches of eggs from April to August. The fecundity of R. oxycephalus was higher, and the size of eggs was larger than that of its closely related species. Conclusions R. oxycephalus is a short-lived, fast-growing, highly fecund, and early-maturing species; therefore, even a short recovery time after overexploitation or disturbance would be of great use for their restoration. Some life history traits of R. oxycephalus demonstrate obvious differences with its closely related species, indicating that latitude and local environment conditions are important selective forces for this species.