Indigenous small fish in rural areas for sustainable use and management: growth and reproduction of Esomus metallicus in central Lao PDR.
The striped flying barb Esomus metallicus is a small indigenous cyprinid found profusely in the plains of Lao PDR; it is an important edible protein resource in rural areas. However, its biological survey, relevant to future stock management and conservation for sustainable use, has been minimal so far. In this context growth and reproduction of E. metallicus in central Lao PDR were investigated via daily age analysis (using otoliths) and gonad analysis of the species collected during different temperature periods, i.e. low temperature periods (November 2009, February to March 2010) and high temperature periods (May to June 2010). Growth patterns in these three periods were each estimated on the basis of daily age (t) and size (Lt) relationships and were fitted by the following Gompertz curves; Lt=46.00.exp[-2.19.exp(-0.026.t)] in November, Lt=40.11.exp[-2.34.exp(-0.029.t)] in February to March and Lt=41.72.exp[-2.46.exp(-0.057.t)] in May to June, respectively. The formulae show that growth during the high temperature period was significantly faster than in the low temperature periods. Based on gonad analysis (gonad somatic index, percent) on females, the reproduction of E. metallicus was more active during high temperature periods than in low temperature periods. Further, differences in oocyte diameters in various size ranges suggested the maturation size of this species to be larger than 40 millimetres standard length with oocytes of approximately 0.5 millimetres in diameter.