Population Parameters and Exploitation Status of Clown Knifefish Notopterus chitala (Hamliton, 1822) from Indus River, Pakistan

Abstract

This study on the population parameters and exploitation status of Clown Knifefish N. chitala (Hamliton, 1822) was conducted from Indus River at Sukkur Barrage, Pakistan. A total of 718 specimens were collected from October 2015 to March 2016. The total length (TL) was ranged from 14-78 cm and average total length was 31±12.266 cm with CV=0.390. The total weight was ranged from 41 to 4939 g and average weight was 434±772.064 g with CV= 1.777 for the combined data. The pooled length weight relationship was estimated as a= 0.0126, b2.8968 R2= 0.984. Length frequency of combined data was used in FISAT-II software which incorporates both von Bertalanffy growth function and ELEFAN-I methods to estimate the growth parameters. The asymptotic length (L∞) and the growth rate (K) were 82.95 cm and 0.390/year, respectively, wherein the hypothetical age at zero length (t0) and goodness of fit or score (Rn) -0.495 year and 0.561 were also estimated correspondingly. The annual total mortality (Z) was 1.03/year, natural mortality (M) was 0.635/year at mean annual surface water temperature of Indus River 21°C, fishing mortality (F) was 0.395/year and exploitation rate (E) was estimated at 0.384/year. The growth performances indices phi prime (Φ’) 3.429 was computed accordingly. The present fishing mortality 0.395/year was smaller than the target biological reference points (Fopt= 0.635/year, Fmax= 1.05/year and F0.1= 0.90/year). These results revealed and confirmed that the stock of N. chitala is not being over-fished. The analysis of current exploitation rate E= 0.384/year was also indicative the sustainable fishery stock in the Indus River as it was lower than current fishing mortality.