Reproductive biology and population dynamics of the five-lined snapper Lutjanus quinquelineatus (Bloch, 1790) from the Gulf of Mannar: implications for establishing minimum legal-size limits
摘要
The present study examines the reproductive traits and population characteristics of Lutjanus quinquelineatus (Family: Lutjanidae), based on specimens collected from the major fish landing centers, viz., Thoothukudi Fishing Harbour (TFH) and Pamban Fish Landing Centre (PFLC) within the Gulf of Mannar Biosphere Reserve between August 2023 and July 2024. The spawning season extended for more than half the year, with two distinct peaks in April and August. The length at first maturity was determined to be 14.4 cm for males and 17.7 cm for females, with females predominating in the commercial catch at a sex ratio of 1:1.33 (M:F). Ova diameter analysis revealed that L. quinquelineatus is a batch spawner with an extended breeding season. The growth parameters were L∞ = 27.30 cm, K = 0.32 year−1, and t₀ = −0.26 year. Mortality rates were Z = 1.96 year−1, M = 0.91 year−1, and F = 1.05 year−1, with an exploitation ratio of 0.53, suggesting that reducing fishing effort could help sustain stock levels. The length–weight relationship revealed positive allometric growth, with the fishery’s size composition ranging from 12 to 22 cm in total length (TL). The catch was predominantly composed of individuals within the 15–18.9 cm length group, making up 74% of the total. The size composition analysis revealed that approximately 62.3% of the commercial catch is below the Lm50. Implementing a minimum legal-size (MLS) regulation could help ensure sustainable management of the fishery.