Critical information on the genus Lethrinus from the Red Sea, applications for fisheries conservation and management

Emperor fishes of the genus Lethrinus are ecologically and commercially important in the Red Sea, supporting artisanal fisheries across Saudi Arabia. Collectively, the Lethrinus species contribute substantially to local fish landings, with average annual catches exceeding 5000 tonnes and high market value in domestic and regional trade. Given their significance, effective management is crucial to ensure sustainability. This study assessed the population biology and exploitation status of eight Lethrinus species: L. borbonicus, L. lentjan, L. microdon, L. mahsena, L. nebulosus, L. obsoletus, L. olivaceus and L. xanthochilus, using fishery-dependent samples collected along the Saudi Arabian Red Sea coast from April 2022 to April 2025. Total length (TL) ranged from 4.9 to 70.5 cm, and total weight (W) from 2.6 to 4067 g. Length-weight relationships varied among species, with growth types spanning positive allometry (b > 3), isometry (b ≈ 3) and negative allometry (b < 3). Von Bertalanffy growth parameters revealed TL_∞ values ranging from 26.5 cm in L. borbonicus to 64.61 cm in L. lentjan, and growth coefficients (K) from 0.13 to 0.41 year^-1. Median length at first maturity ranged from 18.83 cm (L. obsoletus) to 25.68 cm (L. nebulosus). Natural mortality estimates, averaged across methods, ranged from 0.23 to 0.31 year^-1, while total mortality varied from 0.41 to 0.84 year^-1. Corresponding fishing mortality estimates were higher in L. lentjan (0.53 year^-1) and lower in L. obsoletus and L. mahsena (0.41 and 0.42 year^-1, respectively). Exploitation rates (E) exceeded the limit reference point (E = 0.5) remarkably in all three species, indicating ongoing overfishing. Yield-per-recruit and spawning potential ratio analyses (SPR) further confirm reduced reproductive capacity, with SPR values falling below 22% in L. lentjan. Despite mature individuals dominating samples, 47% of legally undersized mature fish in L. lentjan landings were below the current minimum landing size (MLS), signalling poor regulatory compliance. L. mahsena and L. obsoletus are below the SPR threshold (40%) but slightly above safe biological limits. Findings highlight the urgent need for improved management, including species-specific MLS regulations, selective fishing gear and enhanced enforcement, to support the long-term sustainability of Lethrinus stocks in the Red Sea.