Determining the growth parameters and mortality rates of Cobia, Rachycentron canadom (Linnaeus, 1766) in the northern waters of the Persian Gulf (Hormozgan Province)

Abstract

Introduction: The population dynamic of cobia (Rachycentron canadum) was investigated based on length frequency data analysis from October 2017 to December 2018 in the Northern waters of the Persian Gulf from Hormozgan province fishing grounds.
Materials & Methods: The length frequency, growth parameters, and mortality rates of cobia were studied.
Result: From an analysis of 942 specimens ranging from 19 to 159 cm in total length. The most frequent total lengths were situated in the 82-85 cm of class length. The length-weight relationship of 509 specimens was estimated at W=0.0042L3.1162 (r2=0.9852). The result of this study showed that the growth of cobia was categorized as isometric. The calculated r2 shows the high correlation between the length and weight of cobia. Growth parameters K, L∞, Ǿ, and t0 were calculated by the von Bertalanfy growth equation: 0.11 (per year), 168.65 cm, 3.49, and -0.97 respectively. The longevity of cobia was estimated at 28 years, as a long-lived fish in tropical areas. The instantaneous rate of total mortality (Z), natural mortality (M), and fishing mortality (F) rates were estimated using catch curve analysis were 0.30, 0.25, and 0.14 (per year) respectively. The exploitation rate of cobia was estimated at 0.36 which indicates the optimal catch of this fish in the Hormozgan province region.
Conclusion: cobia as one of the high-quality native candidates for introduction into fish farming cages and elimination of dependence on imports of non-native species, the data from this study can be used as initial information in this industry.