Foraging pattern and ingestion rate of invasive crab "Cronius ruber" (Lamarck, 1818), (Decapoda, Brachyura, Portunidae) in Gran Canaria, Canary Islands

Abstract

Foraging pattern of invasive crab, Cronius ruber (Lamarck, 1818) were investigated using specimens collected by hand or with traps during a period between November 2017 to May 2019 around Gran Canaria, Canary Islands, Central-east Atlantic. The stomach contents of 102 crabs, ranging from 40 to 109 mm carapace width, were analysed by sex and maturity condition. The most commonly occurring food categories found in stomach contents consist of mainly large quantities of Brachyura (68.89%), Pisces (32.22%), Bivalvia (27.78 %), Gastropoda (16.67%), Polyplacophora (11.11 %), Equinodermata (26.67%), Annelida (23.33%), unidentifiable matter (28.89%), and debris. Other prey items found in 5–10% of the Cronius ruber stomachs included scales (7.78%), Plantae (7.78%), other crustaceans (6.67%) and Porifera (2.22%). There were significant differences in the diet for the fullness stomach state, however no significant differences are found in the diet for the maturity and sex. Ingestion rate results indicate that there are significant differences between juvenile (40.83 ± 23.28 %, d-1 ) and adult crabs (9.81 ± 7.06 %, d-1 ) (t = 5.567 p= 0.001). Moreover, results indicate that there are significant differences between sex in adult crabs, the average rate of ingestion of adult females (12.74 ± 6.11 % d-1 ); is double that of adult males (6.15 ± 6.52 %, d-1 ) (t = 3.823 p= 0.001). The results obtained from the present study showed that Cronius ruber exhibits, in this region at least, a clear preference for crustaceans.