Resumen.-Se analizó el contenido estomacal de 313 ejemplares juveniles de centolla de ambos sexos con longitudes de caparazón (CL) entre 8,40 y 49,04 mm, estudiándose la influencia del sexo, talla, estado de muda y estación del año. Los animales fueron capturados mediante buceo en muestreos estacionales en el infralitoral rocoso del área central del Golfo San Jorge. Se determinó la frecuencia de ocurrencia (FO) y abundancia relativa (AR) de las presas halladas, estado de repleción y peso del contenido estomacal. Se registró un 14,4% de animales con el estómago vacío, un 55,1% con repleción menor del 50% y un 30,5% mayor al 50%. Los juveniles no se alimentan antes de mudar, durante la muda ni en postmuda reciente. Se identificaron 27 grupos de presas diferentes, incluidas varias especies de algas, protistas e invertebrados. Las mayores FO fueron registradas en algas coralináceas (45,1%), ofiuroideos (34,8%), equinoideos (25,1%), isópodos (21,7%), moluscos bivalvos (19,5%), poliquetos (16,9%) y briozoos (15%). En términos de AR, los principales componentes de la dieta fueron ofiuroideos, isópodos y coralinaceas. La composición de la dieta es diferente en animales menores de 15 mm CL de aquellos mayores a esa talla, debido a la mayor abundancia de isópodos y briozoos en este intervalo. La gran diversidad de presas registradas indica que los juveniles son esencialmente depredadores macrófagos y omnívoros, que aprovechan los complejos hábitats infralitorales rocosos y biogénicos del área estudiada para su alimentación y refugio durante los primeros años de vida.

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The "langostilla", Munida gregaria, also called lobster krill or squat lobster, is a very common galatheid crustacean in San Jorge Gulf and around the southern tip of South America. Previous studies have shown that this species plays an important role in the trophic webs wherever it has been studied. In order to determine its natural food sources, we analyzed 10 samples (30-36 individuals each) taken from different sites in San Jorge Gulf. Moreover, stomach analyses were performed on 32 fish species, 4 mollusk species, and 7 crustacean species from the gulf. The lobster krill is primarily a detritivore or surface deposit-feeder and secondarily a predator and/or scavenger. Its main energy sources are particulate organic matter and their associated bacteria, small live organisms on the surface of the sediment layer (ostracods, copepods, foraminifers, other protists), and animal debris. Polychaetes are the main prey of lobster krill in the study area. This dual complementary feeding behavior is common in the studied galatheids, making them a fundamental link between detritus and benthic and demersal top predators. Some species of these predators constitute important fisheries. Different life-cycle stages of the squat lobster were preyed on by 32 of the examined species. However, the spectrum of predators is still incomplete, with other species feeding on larvae and juveniles of the species.

The settlement and recruitment of the small brachyuran crab Halicarcinus planatus from the central area of Golfo San Jorge, south-western Atlantic Ocean, was studied. Three different artificial collectors were evaluated: smooth-surface panels, panels covered with synthetic lawn and ballasted plastic boxes filled with remains of fishing nets. In addition, plankton samples were taken monthly and water salinity and temperature were recorded. Between July 2006 and June 2007, the collectors were deployed monthly in the subtidal zone of two nearby localities and collected two months later. The recovered crabs were classified into four stages: settlers, recruits, advanced juveniles and mature crabs. There were differences in the presence of stages among collector types and seasons but not between localities. Settlers and recruits were abundant on the panels with synthetic lawn, while late juvenile and mature females were more frequent in the boxes. Larval stages occur between July and February, and only zoeas I and II were found. The males, which were only represented by early juveniles, were exclusively found on the panels with synthetic lawn, from where they would subsequently migrate to cryptic habitats such as the holdfast of Macrocystis pyrifera. Settlement occurs between September and April. Settlers showed a peak in abundance during November–December, while the recruits showed two peaks, one in December and the other in February–March. For late juveniles, the maximum abundance was recorded in April–May. Ovigerous females were found between May and September, when the experiment ended. Settlement and recruitment of H. planatus in Golfo San Jorge occur over a prolonged period. Individuals may undergo shifts in microhabitat use during this period, probably related to the search for food and shelter, and avoidance of predation and cannibalism.