Rev. biol. mar. oceanogr. 48(2): 353-363


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

Julio H. Vinuesa1,2, Martín A.Varisco1,2 & Pamela Balzi1

1Instituto de Desarrollo Costero, Universidad Nacional de la Patagonia San Juan Bosco, Ruta 1 km. 4, (9000), C. Rivadavia, Chubut, Argentina
2Consejo Nacional de Investigaciones Científicas y Técnicas

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Stomach content analysis was performed on 313 juveniles of  Lithodes santolla, with carapace lengths (CL) measuring between 8.40 and 49.04 mm. The influence of season, sex, size and moult stage on their diet were studied.  Crabs were captured seasonally from the rocky sublittoral zone in the central area of San Jorge Gulf using SCUBA. The frequency of prey occurrence (FO), relative abundance (RA), degree of fullness and the stomach content weight were registered. Empty stomachs were found in 14.4% of the specimens, while stomach fullness below 50% occurred in 55.0% of crabs and over 50% in 30.6% of crabs. Juveniles did not feed prior to and immediately after moult. A total of 27 prey groups were identified, which included several species of algae, protists and invertebrates. 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 terms of RA, the main prey items were ophiuroids, isopods and coralline red algae. No significant differences were found in the amount of food consumed and diet composition between sexes. A seasonal variation in the prey species composition was recorded. The diet of crabs smaller than 15 mm CL differed significantly from that of larger juveniles, due to a higher abundance of bryozoans and isopods in smaller juveniles. The great diversity of prey found in juvenile king crab indicates that they are macrophages and opportunistic omnivorous predators, which take advantage of complex rocky and biogenic subtidal habitats for food and shelter.

Key words: Diet, predation, Lithodes santolla, juvenile, coastal waters, omnivory