Stock Assessment of Indian Scad, Decapterus Russelli in Pakistani Marine Waters and Its Impact on the National Economy

Abstract

The stock assessment, of Indian scad Decapterus russelli (Ruppell, 1830) from the northern Arabian Sea in Pakistan was evaluated. The samples of Indian scad (13300 specimens), ranging from 1-31 cm (FL) and 1-400 g (TW) were collected from the commercial fish landing center located at Karachi harbor. The parameters of fish length-weight relationship were calculated from the aggregated data as a=0.0323, b=2.66 with R2=0.954, indicating slightly negative allometric growth between the relationship. The length frequency samples from September 2013 to November 2014 was analyzed using FISAT II software, including the ELEFAN-I method. The growth parameters obtained using ELEFAN I was: L∞=32.55 cm, K=0.750 per year, t0=-0.678 with an Rn value of 0.220. Natural, total and fishing mortality M=1.42 per year, Z=3.84 per year at CI of 95% (CI=3.11-4.58) where F=2.422 per year and exploitation relation E=0.630 were obtained. Growth performance indices for L∞ and W∞ were performed using FiSAT-II program in order to estimate the limit and target reference points of stock exploitation were, Φ'=2.900 per year and Φ=0.170 per year, respectively. The results revealed that the natural fishing level of D. russelli (1.42 per year) was higher than the biological reference points F0.1 (0.85) and Fmax (0.9). Moreover the proportion of current mortality Fcurrent obtained was 0.630, representing that stock of D. russelli as highly exploited.It can be concluded from this study that the population parameters and the stock of D. russelli showed overexploitation in the northern parts of the Arabian Sea coast of Pakistan.