Biometric indices of Scylla serrata (Forskal, 1775): Exploring gender-specific growth patterns from the Cochin Estuary, southwest coast of India

The present study investigated the biometric indices and gender-specific growth patterns of the mud crab <i>Scylla serrata,</i> a commercially important crab species from the Cochin Estuary, southwest coast of India. Biometric indices include size-frequency distribution, carapace width-weight relationship (CW-WR), and condition factors (Fulton's condition factor (K), Allometric condition factor (K<i>a</i>), and relative condition factor (K<i>n</i>)), which are crucial in assessing the biological changes in crabs. The CW-WR and interrelationships between various morphometric characters were estimated using 4022 crabs comprising 2048 males and 1974 females of <i>S. serrata</i> systematically collected from June 2020 to May 2023. Statistical analyses were employed to derive CW-WR for male and female crabs and pooled data. The results indicated a significant correlation between carapace width and weight, revealing potential sex-specific variations in the growth patterns of male <i>S. serrata</i>, expressed as W = 0.0000447 × CW^3.268. At the same time, for females, it is W = 0.0000281∗CW^2.86. Additionally, the relationship for the pooled data, combining both males and females, was W = 0.000103 × CW^3.084. The '<i>b</i>' values for CW-WR in males and females were 3.268 and 2.86, respectively, the '<i>b</i>' values of CW-WR revealed potential gender-specific variations in the growth patterns i.e. Positive allometric growth in males and negative allometric growth in females of <i>S. serrata</i>. The allometric relationships between characters were positive and highly significant. Fulton's condition factor (K) ranged from 0.001 to 0.052 in females and 0.002 to 0.054 in males. The allometric condition factor (K<i>a</i>) ranged from 0.0031 to 0.090 in females and from 0.007 to 0.016 in males. The relative condition factor (K<i>n</i>) ranged from 0.113 to 3.205 in females and from 0.152 to 3.516 in males. This study provides information on the growth and condition of crabs, which will help identify effective fisheries management strategies and contribute to a broader understanding of <i>S. serrata</i> biology.