Assessing fishery status and sustainable exploitation of spotted seabass (Dicentrarchus punctatus) in Bardawil Lagoon, Eastern Mediterranean, Egypt

Abstract

The growth and population parameters of spotted seabass (Dicentrarchus punctatus) in Bardawil Lagoon were investigated to assess their fishery status and propose concrete recommendations for sustainable exploitation. The samples (n = 271) were collected from commercial catches during 2021. As revealed by examining the otoliths, D. punctatus has a short life span of a maximum of four years based on the mean lengths of 20.2, 25.3, 29.7, and 33.5 cm for age groups from I to IV, respectively. The total length-weight relationship equations were W = 0.0120TL^2.9672 for males, W = 0.0127TL^2.9486 for females and W = 0.0124TL^2.9563 for the combined sexes. The von Bertalanffy growth function was L_t = 40.50(1-e^{-0.38(t+0.66)}). The study determined the total and natural mortality rates as 1.58 and 0.79 year⁻¹, respectively, with an exploitation rate (E) of 0.49, which was found close to the optimum value (0.5). However, based on management policies, E was greater than the value corresponding to 50% relative biomass per recruit (E_0.5), which indicates that the current fishing effort is unsustainable. Therefore, to maintain the biomass of spawning stocks, the study recommends a 22.4% reduction in the current exploitation rate through the application of fishing regulations that decrease fishing efforts. Such recommendations can help ensure the sustainable exploitation of spotted seabass in Bardawil Lagoon.