Length‐weight relationship and biological data of a threatened fish,Ptychobarbus chungtienensis (Tsao, 1964) in Bita Lake of Shangri‐La,Yunnan, China

This paper provides the length‐weight relationship (LWR) and other biological information of a threatened plateau freshwater fish species Ptychobarbus chungtienensis in the subfamily Schizothoracinae of the family Cyprinidae, from the Bita Lake of Shangri‐la, in Yunnan, China. The LWR was BW = 0.00954 TL^2.95 for a total of 392 individuals, where the coefficient b was close to 3.0, suggesting a near‐isometric growth in this species. The total length: standard length relationship was TL = 0.399 + 1.151 SL. Fitting a von Bertalanffy growth function to the observed length‐at‐age data resulted in L_(t) = 53.1 (1‐e^?0.08(t?0.2)). The natural mortality rate (M) was 0.20 year^?1. Length at first maturity (Lm) was 20.57 cm, and 6.3 years the theoretical estimated age at first maturity (Am). Ptychobarbus chungtienensis mature gradually beginning in May, reaching a reproduction peak around August, with most individuals completing reproduction by October. The gonadosomatic index (GSI) was highest in August (GSI = 0.1351) and lowest in October (GSI = 0.0467). The male index (GSI = 0.0866) was lower than in females (GSI = 0.1466) (P < 0.05). Mean condition factor (Km) of P. chungtienensis was 0.8500, and not significantly different between sexes (P = 0.124), but differing significantly between seasons. In October the condition factor (Km = 0.9211) was significantly higher than in May (Km = 0.8379) or in August (Km = 0.8412) (P < 0.05).