Size composition and fecundity of the rock crab Grapsus grapsus (Linnaeus, 1758) in the islands of Navachiste Bay, Sinaloa, Mexico

Abstract

The present study  analysed the size composition and fecundity of Grapsus grapsus (Linnaeus, 1758) in the intertidal regions of Guasayeye, La Ventana and San Lucas islands in Navachiste Bay, Sinaloa, Mexico. Samples were collected from November 2017 to October 2018 with a bimonthly periodicity and sampling stations were established in each island. Crab samples were collected randomly at nocturnal low tide. Sex of the crabs was determined and carapace width (CW), length (L) and height (H) in mm, and their weight (W) in g were measured. Biometric correlations were performed. Fecundity was estimated in gravid females. The highest percentage of capture for females was 53.3% whereas for males was 46.7%; and the sex ratio was 1.15:1. The highest percentage was in San Lucas Island (41.4%) and the lowest in La Ventana (27.7%). Maximum CW (69.3 mm) and weight  (137.5 g) were  recorded in San Lucas. Island, while the lowest CW (9.3 mm)  and weight (0.5 g)  were recorded in Guasayeye Island. No significant difference in size  (CW and W) were  observed between  sexes or between islands. The average fecundity for female was 9,245 eggs. A high biometric correlation was obtained (r²=0.98) between the morphometric variables and  G. grapsus was found to have an isometric growth.

Keywords: Fecundity, Grapsus grapsus, Navachiste islands, Population, Rock crab, Size composition,