Biological aspects and population dynamics of the European pilchard <scp> <i>Sardina pilchardus</i> </scp> (Walbaum, 1792) in the southeastern Mediterranean waters

The European pilchard, Sardina pilchardus, is a key small pelagic fish sustaining Mediterranean ecosystems and fisheries. This study represents the first comprehensive biological and population dynamics assessment of the European pilchard by applying the length-based spawning potential ratio (LB-SPR) approach to S. pilchardus in Egyptian Mediterranean waters, providing novel insights into the stock status in the region. A total of 9527 individuals, ranging from 7.2 to 18.6 cm total length, were collected. The length-weight relationship indicated positive allometric growth in both sexes (b = 3.13 for females, b = 3.15 for males), with no significant difference in mean total length between sexes (p = 0.627). The length at first maturity (Lm₅₀) of 10.1 cm is one of the smallest reported for this species in the Mediterranean. Growth parameters of S. pilchardus were estimated using the von Bertalanffy growth function (vBGF), revealing a fast growth rate where L_∞ = 19 cm, K = 0.45 year^-1 and t₀ = -1.45 year. The empirical value of the natural mortality rate (M) was calculated to be 0.80 year^-1. The gonadosomatic index (GSI) indicated a distinct winter spawning season. Selectivity-at-length parameters (SL₅₀ and SL₉₅) were 9.5 and 11.8 cm, respectively. Using LB-SPR method, the estimated mean spawning potential ratio (SPR) of 0.204 and the mean fishing mortality to natural mortality ratio (F/M) of 2.22 suggest that S. pilchardus is overexploited. These findings provide valuable insights for developing effective management strategies of S. pilchardus in the region and contribute to the broader understanding of small pelagic fish dynamics in the Mediterranean ecosystem.