Feeding strategy of early juvenile stages of the southern king crab Lithodes santolla in the San Jorge Gulf, Argentina

Abstract

Stomach content analysis was performed on 313 juveniles of Lithodessantolla, with carapace lengths (CL) measuring between 8.40 and 49.04mm. The influence of season, sex, size and moult stage on their dietwere studied. Crabs were captured seasonally from the rocky sublittoralzone in the central area of San Jorge Gulf using SCUBA. The frequency ofprey occurrence (FO), relative abundance (RA), degree of fullness andthe stomach content weight were registered. Empty stomachs were found in14.4% of the specimens, while stomach fullness below 50% occurred in55.0% of crabs and over 50% in 30.6% of crabs. Juveniles did not feedprior to and immediately after moult. A total of 27 prey groups wereidentified, which included several species of algae, protists andinvertebrates. The higher FO was observed for coralline red algae(41.5%), ophiuroids (34.8%), echinoids (25.1%), isopods (21.7%),bivalves (19.5%), polychaetes (16.6%) and bryozoans (15.0%). In termsof RA, the main prey items were ophiuroids, isopods and coralline redalgae. No significant differences were found in the amount of foodconsumed and diet composition between sexes. A seasonal variation in theprey species composition was recorded. The diet of crabs smaller than 15mm CL differed significantly from that of larger juveniles, due to ahigher abundance of bryozoans and isopods in smaller juveniles. Thegreat diversity of prey found in juvenile king crab indicates that theyare macrophages and opportunistic omnivorous predators, which takeadvantage of complex rocky and biogenic subtidal habitats for food andshelter.