Life history traits and exploitation of Hampala barb (Hampala macrolepidota - Cyprinidae) in a subtropical reservoir (Lao PDR)

摘要

The life history traits of Hampala macrolepidota, a common freshwater fish species in Southeast Asia that is of interest for fisheries and sport fishing, were estimated for a population from Nam Theun 2 Reservoir in Lao. The exploitation status of this species was also characterized using data from landing. Toluidine-stained transverse section of otoliths from 450 specimens, collected between November 2015 and January 2017 (by experimental gillnet fishing and landing surveys), were analysed to identify the periodicity of annulus formation and to age individuals. Length, weight, sex and sexual maturity stage were recorded. Life history traits were characterized by length-weight and length-age relationships. The periodicity of annulus formation was annual, with complete formation of the translucent zone at the end of the warm and dry season and the beginning of the warm and wet season (May-June). The length at first sexual maturity of females was estimated to occur at a standard length of 212 mm and at 3.3 years old (50% of matured females). The condition factor, which was between 1.04 and 1.09, was lower than for other studied populations. H. macrolepidota in the Nam Theun 2 Reservoir had a relatively slow growth (0.24 yr(-1)) with a relatively short lifespan (maximum age of approximately 9 years old). The species exploitation in the reservoir mainly concerned individuals that had a standard length between 120 and 220 mm, meaning that 67% of landed individuals did not have time to reproduce before capture. The exploitation rate was 0.87, and according to the probability of capture, individuals had 50% chances of being caught after 182.5 mm, preventing them from taking part in the stock renewal. The present study suggests that the H. macrolepidota population in the reservoir is overexploited. These new findings should be considered for further improvements in fishery management and the sustainability of fisheries.