Age, growth and mortality of Streaked Gurnard (Trigloporus lastoviza, Bonnaterre, 1788) in the Egyptian Mediterranean waters off Alexandria

Abstract

Age, growth and mortality of Streaked Gurnard Trigloporus lastoviza from the Egyptian Mediterranean waters off Alexandria were investigated between the period from July 2009 and August 2010. The observed maximum age was 4 years for both sexes based on otolith readings. The length-weight relationship was estimated as W=0.0088L3.0694 (r=0.9854); W=0.0085L3.0836 (r=0.9803) and W=0.0106L3.0058 (r=0.9853) for males, females and combined sexes respectively. The von Bertalanffy growth equations for length were: Lt=27.17 (1-e-0.3466 (t+1.01), Lt = 27.0 (1 - e -0.3703 (t + 0.93) and Lt = 26.92 (1 - e -0.3699 (t + 0.92) for males, females and combined sexes respectively. The growth performance index value (Φ) was calculated as 2.41, 2.43 and 2.43 for males, females and combined sexes respectively. The back calculated data indicated that the growth in length of T. lastoviza was highest at the end of the first year of life, followed by a gradual continuous decrease throughout the fish life. Total, natural and fishing mortalities were estimated for combined sexes as 1.51, 0.43 and 1.08 year -1 respectively. The results indicate that population is overexploited (E = 0.72) and suffering from high fishing pressure.