Population dynamics of Nile Tilapia (<i>Oreochromis niloticus</i>) at Chashma Barrage, Pakistan

Abstract

Growth and mortality parameters of <i>Oreochromis niloticus</i>, 480 samples collected through four research trawls during the months of April, May, June and July of 2014, were evaluated by using FiSAT-II computer package. Length-weight parameters were found to be as <i>W</i> = 0.001 * <i>L </i>^2.144 (R² = 0.939), where <i>W</i>, <i>L</i> and R² represents weight, length and coefficient of determination. Computed von Bertalanffy growth functions, ELEFAN method, were <i>L_∞</i> (asymptotic length) = 227.85 mm (FL) and <i>K</i> (growth coefficient) = 0.070 year^-1 respectively. Estimated value of <i>t₀</i>(hypothetical length at which age is zero) remained -0.158 year^-1 whereas R_n (goodness of fit) was 0.182. <i>Z </i> (annual mortality rate) was evaluated as 1.11 with its 95% confidence interval at (0.74 – 1.49) and <i>M</i> (natural mortality) was 0.16. The value of fishing mortality (<i>F</i>) and exploitation ratio (<i>E</i>) was 0.95 year^-1 and 0.85 year^-1 correspondingly. <i>F_max</i>, <i>F_0.1</i> and <i>F_current</i> were evaluated as 0.2 year^-1, 0.15 year^-1 and 0.15 year^-1 correspondingly. <i>Φ</i> (growth performance index) was computed as 3.560. Current study suggests that the capture of this fishery resource should not exceed from current catch level.