Population Structure and Reproductive Biology of the Pebble Crab, Philyra corallicola (Decapoda: Brachyura: Leucosiidae) off Karachi Coast, Pakistan

This study represents the initial contribution to understanding the population structure and reproductive biology of the pebble crab Philyra corallicola, inhabiting the intertidal zone of Clifton, Pakistan. Over a span from November 2009 to February 2011, a total of 501 individuals were systematically collected, and their reproductive and relative growth were meticulously analyzed. Population data revealed unimodal size-frequency distributions in males, females and combined sex, with males exhibiting larger carapace width and length, as well as greater total weight compared to females. Across all morphometric relationships, males, females, and combined sex displayed negative allometry. While the overall sex ratio adhered to a normal distribution of 1:1 (χ2 = 0.2; P > 0.05), examination of males and females across different size classes revealed a skew towards females in smaller size classes and towards males in larger size classes. P. corallicola displayed a continuous reproductive cycle, with the highest percentage of ovigerous females observed in March and June–August. Spawning (% of ovigerous females) exhibited a significant negative correlation with salinity (r = -0.576; P = 0.019) and significant positive correlations with temperature (r = 0.599; P = 0.014) and photoperiod (r = 0.505; P = 0.046).