Growth Pattern of the Golden Gray Mullet, Liza Aurata (Mugilidae) in the Southern Mediterranean Coast (Libya)

This study aimed to establish the von Bertalanffy growth model of the golden gray mullet Liza aurata in lagoonal habitats of the southern Mediterranean, as exemplified by Umm Hufayn, a brackish lagoon in eastern Libya. Eighty L. aurata fish collected randomly from the artisanal catch of Umm Hufayn were used in the study. The length-weight relationship, and the fish length-at-age data, used to calculate the von Bertalanffy parameters (L_∞, K, t₀, and W_∞) were obtained from another two complementary studies based on the same 80 fish sample. Four aging techniques were used: counting annuli on opercula and scales, the fish-length frequency distribution, and the “average” of the three techniques. The mean length of the studied fish was 21.33cm, corresponding to a mean weight of 89.01g. The established von Bertalanffy growth models were: L_t=56.765*(1-exp(-0.070*(t+4.440))), Ø^/ =2.3532, based on opercula; L_t=39.02*(1-exp(-0.1645*(t+2.8))), Ø^/ =2.3987, based on scales; L_t=40.0313*(1-exp(-0.1549*(t+3.0204))), Ø^/ =2.3949, based on the length Frequency distribution, and L_t=49.7049*(1-exp(-0.0949*(t+3.9573))), Ø^/ =2.370, based on the “average”. The model obtained from grand averaging of L_∞, K, t₀, and W_∞ obtained from the four aging techniques was L_t=45.2704*(1-exp(-0.1298*(t+3.42))), Ø^/ =2.4249. The predictability of all these models was high, as can be concluded from the close values of their Ø^/, and the closeness of the predicted length-at-age values to measured values; their plots almost overlapped. Derivatives of the above models (W_t, t_L, ∆t) were also calculated.

Keywords: Libya., Liza aurata, golden mullet, southern Mediterranean, von Bertalanffy growth