Demographic Characteristics and Exploitation Status of the Blue Swimming Crab Portunus pelagicus (Linnaeus, 1758) Along the Palk Bay Coast, Southeast India

Pearlin Arul, Granap S and Durairaja, R and Jayakumar, N and Ranjith, L and Sudhan, C and Karuppasamy, K and Kalaiarasan, M and Jeyabalan, Joyson Paul and Nandhakumar, M (2025) Demographic Characteristics and Exploitation Status of the Blue Swimming Crab Portunus pelagicus (Linnaeus, 1758) Along the Palk Bay Coast, Southeast India. Thalassas: An International Journal of Marine Sciences, 41. ISSN 2366-1674

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Abstract

The demographic characteristics and exploitation status of Portunus pelagicus (Linnaeus, 1758) along the Palk Bay coast were investigated based on 6,814 specimens (3,425 males and 3,389 females) collected fortnightly from four major commercial crab landing centers between June 2024 and May 2025. Morphometric analyses revealed distinct growth patterns: carapace width‒weight relationships demonstrated isometric growth (b = 3.043), whereas carapace length‒weight relationships exhibited positive allometric growth (b = 3.162). Analysis of covariance (ANCOVA) revealed a significant difference (p = 0.003) in the mean carapace width and weight between males and females. The length-frequency distribution was analysed using the FiSAT II tool. The growth parameters asymptotic length (L∞), growth coefficient (K), and theoretical age at zero length (t0) were determined to be 17.96 cm, 1.3 yr⁻¹, and − 0.855 year respectively. Mortality analysis showed total mortality (Z = 5.20 yr⁻¹) and fishing mortality (F = 2.72 yr⁻¹) exceeded natural mortality (M = 2.48 yr⁻¹). The recruitment patterns showed year-round continuity, with pronounced peaks occurring during April and August. Virtual population analysis (VPA) revealed the highest fishing mortality at 11–12 cm. The exploitation ratio (E = 0.52) closely approaches the optimal threshold of 0.5, suggesting that the current fishing intensity operates near the maximum sustainable yield (MSY). These findings emphasize the need for adaptive fisheries management including minimum legal-size limits (> 11–12 cm), closed seasons during recruitment peaks (April-August), and selective fishing gear to prevent overexploitation of this economically important crustacean resource in Palk Bay.

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