SUMMARY: This paper comprises the decapod crustacean material collected during the "Victor Hensen" campaign 1994 and during the last phase of "Polarstern" cruise ANT XIII/4 in 1996. Sampling covered waters of medium and greater depth in the Straits of Magellan, the channels towards the south, and the area south of the Beagle Channel including the northern slope of the Drake Passage. 30 species of decapods were found, which is considered a good result taking into account that the species restricted to the intertidal and the upper subtidal, which were not subject of this study, are missing. Anomurans were the dominant group, followed by brachyurans and caridean shrimps. Additionally one palinuran (Stereomastis suhmi; n=8) and a single specimen of the astacuran Thymops birsteini were found. Dominance patterns changed considerably from the Straits of Magellan to the channel system south of the Strait, and again to the area south of the Beagle and the northern slope of the Drake Passage. Among the top dominants were the galatheid Munida spp., which in the southernmost area numerically contributes >90% to the catches, the brachyuran crabs Peltarion spinosulum and Eurypodius latreillii, the hermit crab Pagurus comptus, and the caridean shrimps Austropandalus grayi and Pasiphaea acutifrons. Munida spp. and P. spinosulum also revealed the highest frequency of occurrence at 49% and 45% of the stations, respectively, followed by E. latreillii, P. comptus, and A. grayi. Regional and bathymetric distribution of the principal species are given. The depth range of some species was found to be very wide (Campylonotus semistriatus, Munida spp., E. latreillii, P. spinosulum) whereas others were restricted to relatively shallow waters (Pagurus gaudichaudii, Lithodes santolla, Campylonotus vagans, A. grayi) or great depth (Nematocarcinus lanceopes, Stereomastis suhmi). It should be mentioned, however, that sampling depths differed greatly in the areas of study. Contrary to the Antarctic, the Magellan region reveals a strong dominance of reptant decapods whereas caridean shrimps play a minor role in that region. This dominance pattern is valid even for the southernmost areas of the region. The northern slope of the Drake Passage is characterized by a mixture of cold-temperate and Antarctic elements which make it a transitional area between the two continents.Key words: Decapoda, species composition, distribution, abundance, Straits of Magellan, Beagle Channel, Drake Passage RESUMEN: COMPOSICIÓN DE ESPECIES Y DISTRIBUCIÓN DE LOS CRUSTÁCEOS DECÁPODOS EN LAS AGUAS DE LA PATAGONIA Y DETIERRA DEL FUEGO, AMÉRICA DEL SUR. -En este trabajo se analiza el material de crustáceos decápodos recolectado en la Campaña "Victor Hensen" 1994 y en la última etapa de la campaña "Polarstern" ANT XIII/4 en 1996. El muestreo cubrió las aguas de mediana y mayor profundidad en el Estrecho de Magallanes, los canales del sur y el área al sur del Canal del Beagle incluyendo la vertiente norte del Paso de Drake. Se registraron 30 especies de decápodos, lo cual ...

RESUMEN: Se analizan 88 ejemplares de centolla capturados con trampas en aguas profundas del Océano Austral, próximas al continente Antártico (Subáreas estadísticas 88.3, 48.1 y 48.2). Los ejemplares de Paralomis birsteini Macpherson, 1988, se capturaron en los montes submarinos de Gerlache y en los alrededores de la isla Pedro I, en el mar de Bellingshausen; en el talud continental al oeste de la Península Antártica y en el Mar de Escocia, al norte de las islas Orcadas del Sur, en profundidades entre 621 y 1876 m. Los especímenes presentaron longitudes cefalotorácicas entre 50,8 y 110,2 mm y peso promedio de 249 g. Los rendimientos, respecto al total de trampas utilizadas en cada subárea, correspondieron a 87,3 g/trampa en la Subárea 88.3; 2,2 g/trampa en la Subárea 48.1; y, 548,8 g/trampa en la Subárea 48.2. Además, se discute la presencia de la familia Lithodidae en el océano Austral.

RESUMEN: Se identifica y describe las cinco especies de crustáceos decápodos capturados en faenas de pesca exploratoria y experimentales realizadas con trampas caladas en torno a las islas Robinson Crusoe y Santa Clara, archipiélago de Juan Fernández, Chile (33°38'S, 78°49'W), entre 50 y 1000 m de profundidad, de noviembre de 1996 a junio de 1997. Las especies encontradas corresponden a Jasus frontalis (50-100 m), Projasus bahamondei (250 m), Paromola rathbuni (100-300 m), Chaceon chilensis (200-1000 m) y Ovalipes trimaculatus (100 m). Se discute la distribución de estas especies, como también los posibles mecanismos de colonización y renovación de sus poblaciones que habitan en islas y montañas submarinas del océano Pacífico suroriental, notablemente distanciadas entre sí y del continente sudamericano.

The marine ecosystem of the Chilean Patagonia is considered structurally and functionally unique, because it is the transition area between the Antarctic climate and the more temperate Pacific region. However, due to its remoteness, there is little information about Patagonian marine biodiversity, which is a problem in the face of the increasing anthropogenic activity in the area. The aim of this study was to analyze community patterns and environmental characteristics of scavenging crustaceans in the Chilean Patagonian Sea, as a basis for comparison with future situations where these organisms may be affected by anthropogenic activities. These organisms play a key ecological role in marine ecosystems and constitute a main food for fish and dolphins, which are recognized as one of the main tourist attractions in the study area. We sampled two sites (Puerto Cisnes bay and Magdalena sound) at four different bathymetric strata, recording a total of 14 taxa that included 7 Decapoda, 5 Amphipoda, 1 Isopoda and 1 Leptostraca. Taxon richness was low, compared to other areas, but similar to other records in the Patagonian region. The crustacean community presented an evident differentiation between the first stratum (0-50 m) and the deepest area in Magdalena sound, mostly influenced by Pseudorchomene sp. and a marked environmental stratification. This species and Isaeopsis sp. are two new records for science. The discovery of undescribed species evidences that this region needs further studies exploring its biodiversity, which is most likely being already impacted by anthropogenic pressure. The Chilean Patagonian region, located between 41°20′S and 55°58′S of latitude in South America, includes one of the most complex systems of channels and fjords of the planet and holds some of the largest estuarine areas of the world 1. It contains approximately 1,600 km of shoreline and a surface of 2,400 km 2 , being a transition zone of climatological, biogeographical and biological conditions between the Antarctic and the temperate Pacific regions 2. This situation produces an ecosystem that can be considered structurally and functionally unique 3. The ecological and physicochemical characteristics of a fjord are mainly controlled by the interaction of fresh water flowing from the rivers and the entrance of sea water depending on marine currents and tides 4. This creates a strong vertical gradient characterized by a halocline (i.e., a rapid vertical change in salinity), with brackish surface waters and saline intermediate and deep waters. Such marked stratification creates specific environmental conditions that often determine the presence of different species assemblages 5. Within the Chilean Patagonia, the Aysén region is subjected to different anthropogenic activities that have the potential to affect the marine biodiversity.

Our knowledge on the status of Hemigrapsus crenulatus (H. Milne Edwards, 1837) populations along the Chilean coast is scarce. The aim of the present study was to quantitatively estimate the spatial distribution and abundance of Hemigrapsus crenulatus in the Puerto Cisnes estuary (44°S, Aysen region, Chilean Patagonia). The spatial distribution appeared to be aggregated, with 3.64 ± 7.99 ind/m2 as gross density, and 10.50 ± 10.62 ind/m2 as a potential ecological density, i.e., if the quadrants with zero individuals are not taken into consideration. The equation of the negative binomial distribution was: where: . The average density of Hemigrapsus crenulatus under stones is lower if all beach surfaces are considered. Its abundance or dominance on estuarine beaches probably would be due to the fact that this species is one of the crustaceans of the lower intertidal level that can survive under a wide range of salinity values.