Species composition and distribution of decapod crustaceans in the waters off Patagonia and Tierra del Fuego, South America

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 southermost 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.