Age and Growth of the Silver Grunt Pomadasys argenteus (Forsskal, 1775) in Jizan Fisheries, Saudi Arabia

Abstract

The silver grunt Pomadasys argenteus is one of the commercial fish species in the family Haemulidae widely distributed in the Indo-West Pacific (from Red Sea to Fiji). The age of this species was determined using scales. The back-calculated lengths-at-ages were estimated using the body proportional hypothesis (BPH) based on the relation between the body length and scale measurements. The relationship between the scale radius (S) and total length (L) could be described by the linear form: L = 4.632 S - 4.813 (R² = 0.93) for males, L = 4.37 S - 2.761 (R² = 0.94) for females, and L = 4.39 S - 3.28 (R² = 0.95) for pooled sexes. Seven age groups were determined for females (I⁺ to VII⁺), and five groups for males (I⁺ to V⁺). Growth parameters were estimated from the growth rates and found to be L_¥ (asymptotic length) = 52.33 cm, K (growth coefficient) = 0.197 yr^-1, and t_o (supposed age at zero length) = -0.74 yr for males; L_¥ = 57.39 cm, K = 0.174 yr^-1, and t_o = -0.82 yr for females; and L_¥ = 56.07 cm, K = 0.181 yr^-1, and t_o = -0.79 yr for pooled sexes. The length-weight relationship was described by the nonlinear power equation: W = 0.0130 L^3.014 (R² = 0.99) for males, W = 0.0146 L^2.98 (R² = 0.99) for females, and W = 0.0138 L^3.00 (R² = 0.99) for pooled sexes. The growth of this species is isometric where the regression slope for both sexes does not differ significantly from the value ' 3 ' of the isometric growth. The life span (maximum age) was estimated to be 16.4 yr for females, 14.5 yr for males, and 15.8 yr for combined sexes, indicating that the silver grunt in Jizan fisheries is a moderate sized fish species (between 10 to 20 yrs.).