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Piola A.R.,Servicio de Hidrografia Naval | Piola A.R.,University of Buenos Aires | Martinez Avellaneda N.,University of Hamburg | Guerrero R.A.,Instituto Nacional Of Investigacion Y Desarrollo Pesquero | And 5 more authors.
Ocean Science | Year: 2010

The Patagonia continental shelf located off southeastern South America is bounded offshore by the Malvinas Current, which extends northward from northern Drake Passage (∼55deg; S) to nearly 38deg; S. The transition between relatively warm-fresh shelf waters and Subantarctic Waters from the western boundary current is characterized by a thermohaline front extending nearly 2500 km. We use satellite derived sea surface temperature, and chlorophyll-a data combined with hydrographic and surface drifter data to document the intrusions of slope waters onto the continental shelf near 41deg; S. These intrusions create vertically coherent localized negative temperature and positive salinity anomalies extending onshore about 150 km from the shelf break. The region is associated with a center of action of the first mode of non-seasonal sea surface temperature variability and also relatively high chlorophyll-a variability, suggesting that the intrusions are important in promoting the local development of phytoplankton. The generation of slope water penetrations at this location may be triggered by the inshore excursion of the 100 m isobath, which appears to steer the Malvinas Current waters over the outer shelf. Source

Menni R.C.,CONICET | Jaureguizar A.J.,Instituto Nacional Of Investigacion Y Desarrollo Pesquero | Stehmann M.F.W.,Ichthys Consultant | Lucifora L.O.,Dalhousie University | Lucifora L.O.,CONICET
Biodiversity and Conservation | Year: 2010

For more than a century, two major zoogeographic provinces have been proposed for the southwestern Atlantic: A warm water Argentinean Province from Rio de Janeiro (23°S, Brazil) to Valdés Peninsula (42°S, Argentina), and a cold water Magellanic Province from Valdés Peninsula to Cape Horn. This zoogeographic scheme has been recognized so far using data covering only parts of the whole geographic area. Here, we test the validity of this scheme by analyzing the distribution of sharks, skates, rays and chimaeras, using data from research cruises covering the entire area. We used cluster, similarity and dissimilarity analyses to identify species assemblages, and canonical correspondence analysis to identify the main environmental variables affecting the composition of the assemblages. The distribution of chondrichthyan assemblages strongly supports the current zoogeographic scheme and identifies a previously unknown and distinctive deep water zoogeographic unit off southern Brazil. Both, the Argentinean and Magellanic Provinces had extensive internal structure, with four and three subareas identified in each of them, respectively. These subareas correspond, with slight differences, to previously proposed zoogeographical districts within the Argentinean Province and confirm ecological differences within the Magellanic Province. Species composition had the highest correlation with depth and bottom water temperature. Since the distribution of anthropogenic disturbances in the region is uneven, different assemblages can be subjected to different impacts. Our results provide an objective basis to establish priority areas for the conservation of chondrichthyans in the southwestern Atlantic. © Springer Science+Business Media B.V. 2009. Source

Favero M.,CONICET | Blanco G.,Instituto Nacional Of Investigacion Y Desarrollo Pesquero | Copello S.,CONICET | Pon J.P.S.,CONICET | And 4 more authors.
Endangered Species Research | Year: 2013

Seabird mortality associated with fisheries is one of the major threats leading to population decreases of certain species, particularly albatrosses and petrels. The present study was conducted to (1) analyze seabird bycatch in the Argentinean demersal longline fishery during the decade 2001 to 2010, (2) provide a baseline of the levels of incidental mortality prior to the implementation of the National Plan of Action-Seabirds, and (3) characterize in space and time the occurrence and intensity of seabird mortality. Fishing effort decreased from some 30 million to 5 million hooks set per year, and the overall bycatch rate for the whole period was 0.033 (0.019 SE) birds per 1000 hooks. The estimated total mortality for the 10 yr period was 7470 ± 2449 seabirds, the majority being black-browed albatrosses and white-chinned petrels. Seabird mortalities decreased by 1 order of magnitude towards the end of the decade, not due to lower bycatch rates but to a drop in the number of hooks set per year. The progress achieved so far in Argentina is important, but if seabird bycatch is to be reduced to negligible levels, it is imperative that the National Plan of Action-Seabirds is effectively implemented and that the longline fishery comply with the conservation measure calling for the use of mitigation methods that came into effect in 2010. Other management-related actions, such as the increase of capacities within the National Observer Program and the refinement of seabird sampling protocols, will have an effect not only in the longline but also in the large trawl fishery, where seabird bycatch has also been documented. © Inter-Research 2013. Source

Barbini S.A.,University of the Sea | Barbini S.A.,National University of Central Buenos Aires | Lucifora L.O.,CONICET | Lucifora L.O.,Centro Of Investigaciones Ecologicas Subtropicales Cies | Hozbor N.M.,Instituto Nacional Of Investigacion Y Desarrollo Pesquero
Marine Biology Research | Year: 2011

Dietary shifts with size, maturity stage, season, and bottom type selection of Zapteryx brevirostris were evaluated, using generalized linear models. In terms of the index of relative importance, the most important prey were amphipods (39.17%), polychaetes (22.33%) and lancelets (20.33%), followed by decapods (8.93%), cumaceans (5.41%) and isopods (3.41%). Z. brevirostris consumed mainly polychaetes and amphipods in spring and summer, more cumaceans in winter, consumed more lancelets in spring, and preyed more heavily on decapods and isopods in summer. As Z. brevirostris increased in size, the consumption of decapods, polychaetes and isopods was higher, but the consumption of amphipods decreased. Mature individuals of Z. brevirostris consumed more lancelets than juveniles. Z. brevirostris selected sand over other bottom types. The diet of Z. brevirostris can be influenced by the selectivity of this species for sandy bottoms. As sandy bottoms are exposed to a high intensity of bottom trawling, the positive selection of sandy bottoms increases the vulnerability of Z. brevirostris by exposing it to fishing mortality. © 2011 Taylor & Francis. Source

Schejter L.,CONICET | Schejter L.,Instituto Nacional Of Investigacion Y Desarrollo Pesquero | Escolar M.,Instituto Nacional Of Investigacion Y Desarrollo Pesquero
Pan-American Journal of Aquatic Sciences | Year: 2013

In this contribution we highlighted the importance of the gastropod Adelomelon ancilla (living and empty shells) as settlement substrate for the sea anemones Antholoba achates and Isotealia antarctica in soft bottoms of the SW Atlantic Ocean. Fifty percent of the sampled shells of A. ancilla presented at least one epibiotic anemone and up to a maximum of 6 anemones were reported in one living individual. Adelomelon ancilla shells are the first settlement substrate reported for I. antarctica. We also recorded the use of empty shells by Pagurus comptus and Propagurus gaudichaudii, as far as the less frequent record of other invertebrates and gastropod egg cases attached to the empty shells. These results are compared with the epibiotic organisms recorded on Odontocymbiola magellanica, another volutid species that shares the same habitat. Source

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