scholarly journals Population structure, distribution and abundance patterns of the patagonian smoothhound Mustelus schmitti Springer, 1939 (Chondrichthyes, Elasmobranchii, Triakidae) in the rio de La Plata and inner continental shelf , sw Atlantic ocean (34º30'-39º30'S)

2007 ◽  
Vol 55 (3) ◽  
pp. 167-177 ◽  
Author(s):  
María Cristina Oddone ◽  
Laura Paesch ◽  
Walter Norbis ◽  
Gonzalo Velasco
Keyword(s):  
Population Structure ◽  
Atlantic Ocean ◽  
Continental Shelf ◽  
Significant Variation ◽  
Length Distribution ◽  
La Plata ◽  
Abundance Patterns ◽  
Sw Atlantic ◽  
Inner Continental Shelf ◽  
Mustelus Schmitti

A total number of 4824 Mustelus schmitti was sampled. Females ranged from 25 to 93 cm in spring and from 28 to 90 cm in summer. Males ranged from 34 to 82 and from 28 to 77 cm, respectively. Length composition of the population showed significant differences between spring and summer being females larger than males. Total length distribution did not show significant differences between cruises. Males density varied significantly between cruises while for the females no significant variation was observed. In the spring cruise, both sexes occurred at depths lower than 50 m. Females occurred in the whole area with adult occurrence only above 35°30'S. Mature males occurred throughout the area, immature males occurring in two trawls in Samborombón Bay. The summer cruise showed a discontinuous distribution of the species along the study area resulting in spatial segregation in two groups with immature females predominating in both of them.

scholarly journals Composition of Trichiuridae and Gempylidae larvae (Teleostei) and their association with water masses in the Southwest Atlantic Ocean

2009 ◽  
Vol 38 (4) ◽  
Author(s):  
Paulo Júnior ◽  
Christiane de Souza ◽  
Graciela Weiss
Keyword(s):  
Temperature Gradient ◽  
Atlantic Ocean ◽  
Continental Shelf ◽  
Mesh Size ◽  
Water Masses ◽  
Southwest Atlantic ◽  
Patos Lagoon ◽  
La Plata ◽  
Tropical Water ◽  
The Relationship

Composition of Trichiuridae and Gempylidae larvae (Teleostei) and their association with water masses in the Southwest Atlantic OceanIn this paper the relationship between temporal changes in the occurrence of water masses and Trichiuridae and Gempylidae larvae composition and distribution in the Southwest Atlantic ocean were analysed between 25° and 40° S. Ichthyoplankton was collected during the three expeditions of the Subtropical Convergence Project: Winter and Spring 1977, Autumn 1978 and Summer 1981, realized in the Southwest Atlantic waters. Oblique tows were conducted using a Hensen net with 250 μm mesh size. Steep salinity and temperature gradient were found, where the river outflows from La Plata river (Argentina) and Patos Lagoon (Brazil) met the Tropical Water over the continental shelf between 32 and 36° S. We examined 524 Hensen-net samples that contained about 283 larvae from five species of Trichiuridae and Gempylidae. The most abundant and frequent specie were

scholarly journals Size and sex composition of two species of the genus Atlantoraja (Elasmobranchii, Rajidae) caught by the bottom trawl fisheries operating on the Uruguayan continental shelf (southwestern Atlantic Ocean)

2011 ◽  
Vol 59 (4) ◽  
pp. 357-364 ◽  
Author(s):  
Luis Orlando ◽  
Ines Pereyra ◽  
Laura Paesch ◽  
Walter Norbis
Keyword(s):  
Continental Shelf ◽  
Significant Variation ◽  
Length Distribution ◽  
Seasonal Distribution ◽  
Size At Maturity ◽  
Southwestern Atlantic ◽  
Spatial And Seasonal Variation ◽  
Southwestern Atlantic Ocean ◽  
Trawl Fisheries ◽  
Size And Sex Composition

In this work we analyzed the spatial and seasonal variation of length distribution, sexual proportion and mature dominance for Atlantoraja cyclophora and A. castelnaui, at the Uruguayan continental shelf. There were significant differences in total length (TL) composition between sexes, being females bigger than males for both species. Atlantoraja cyclophora showed a relatively uniform length distribution between inner and outer shelf. There were no major variations in the sex compositions and in the mature dominance between seasons, suggesting no temporal variation. Atlantoraja castelnaui showed a significant variation in its spatial and seasonal distribution. Individuals were smaller in inner shelf, pointing out the existence of juvenile zone in areas up to 50 m depth. A tendency to capture smaller individuals towards the end of the year was observed. In all seasons over 50% of females were caught below the estimated size at maturity, suggesting that this species is highly susceptible to exploitation.

scholarly journals Remarks on the morphology and distribution of some rare centric diatoms in southern Brazilian continental shelf and slope waters

2012 ◽  
Vol 60 (4) ◽  
pp. 415-427 ◽  
Author(s):  
Marinês Garcia ◽  
Clarisse Odebrecht
Keyword(s):  
Atlantic Ocean ◽  
Continental Shelf ◽  
Southwestern Atlantic ◽  
Patos Lagoon ◽  
La Plata ◽  
Centric Diatoms ◽  
Southwestern Atlantic Ocean ◽  
The Family ◽  
Scanning Electron Microcopy ◽  
First Time

This paper provides information on the morphology and occurrence of extant diatoms of the family Asterolampraceae and Azpeitia species of the southernmost Brazilian continental shelf and slope waters in the Southwestern Atlantic Ocean (28 -34ºS), under the influence of Tropical, Subtropical, Subantarctic Waters, terrestrial discharges from La Plata River and Lagoa dos Patos lagoon. Plankton was sampled (20 µm net; vertical hauls) at the same 27 stations in winter 2005 and summer 2007. Among Asterolampraceae, Asteromphalus flabellatus was the most frequent species (57% of samples) observed mainly in winter samples (92%) in Subtropical Shelf Water but also under the influence of La Plata River plume (salinity <35). Lower frequencies were observed for Asterolampra marylandica, Asteromphalus elegans, Asteromphalus heptactis and Spatangidium arachne. Four species of Azpeitia were observed: A. barronii and A. neocrenulata for the first time in the South Atlantic Ocean while A. africana and A. nodulifer had already been registered in equatorial and southern areas of Brazil. All Azpeitia species were rare (19%) in offshore samples (100-200 m depth. Remarks on the morphology based on light and scanning electron microcopy observations are provided along with their distribution in the study area.

A new species of Pachycheles (Crustacea: Anomura: Porcellanidae), with taxonomic remarks on two other porcelain crabs from the remote oceanic archipelago of Trindade and Martin Vaz, South Atlantic Ocean

Zootaxa ◽  
2017 ◽  
Vol 4299 (4) ◽  
pp. 546 ◽  
Author(s):  
LUCIANE AUGUSTO DE AZEVEDO FERREIRA ◽  
MARCOS TAVARES
Keyword(s):  
New Species ◽  
Atlantic Ocean ◽  
Continental Shelf ◽  
Abdominal Segment ◽  
South Atlantic ◽  
South Atlantic Ocean ◽  
Western Atlantic ◽  
Porcelain Crabs ◽  
Inner Continental Shelf ◽  
A New Species

Three species in two genera of porcelain crabs are reported from the remote oceanic archipelago of Trindade and Martin Vaz one of which, Pachycheles meloi, new to science. The new species is morphologically similar to Pachycheles riisei (Stimpson, 1858) from the inner continental shelf between Florida (USA) and São Paulo (Brazil), of which Pachycheles meloi sp. nov. differs by a suite of carapace and appendage characters, including the presence of a pair of male gonopods on the second abdominal segment (absent in P. riisei). The new species is additionally compared to other congeners. Opportunity is taken to elaborate on the taxonomy of Petrolisthes amoenus (Guérin-Méneville, 1855) and Petrolisthes marginatus (Stimpson, 1859). The Trindade and Martin Vaz Archipelago contain a strongly depauperate porcellanid fauna of western Atlantic affinities. 

Appendicularian assemblages and their space–time variability off the La Plata River, SW Atlantic Ocean

2009 ◽  
Vol 85 (1) ◽  
pp. 97-106 ◽  
Author(s):  
Mariela L. Spinelli ◽  
Patricia Martos ◽  
Graciela B. Esnal ◽  
Fabiana L. Capitanio
Keyword(s):  
Atlantic Ocean ◽  
Space Time ◽  
Time Variability ◽  
La Plata ◽  
Sw Atlantic

Seabirds, environmental features and the Argentine anchovy Engraulis anchoita in the southwestern Atlantic Ocean

2020 ◽  
Vol 651 ◽  
pp. 199-213
Author(s):  
PL Costa ◽  
L Bugoni ◽  
PG Kinas ◽  
LASP Madureira
Keyword(s):  
Atlantic Ocean ◽  
Continental Shelf ◽  
Bottom Water ◽  
Close Association ◽  
Information Criterion ◽  
Bottom Water Temperature ◽  
Environmental Features ◽  
Southwestern Atlantic Ocean ◽  
Sw Atlantic ◽  
The Difference

As top predators in marine environments, seabirds frequently respond to the presence of their main prey, and both predators and prey are usually associated with specific environmental features. We investigated the variability in the presence and density of flying seabirds (mostly Procellariiformes and Charadriiformes) and Magellanic penguins Spheniscus magellanicus along the southwestern (SW) Atlantic continental shelf. Five acoustic assessment surveys were conducted to determine the biomass of the Argentine anchovy Engraulis anchoita, and seabird counts and the collection of oceanographic data were conducted simultaneously with the surveys between June and October 2010. Generalized linear mixed models (GLMMs) were fitted to test the effect of anchovy density and environmental variables on seabird density. Sea surface temperature was significant for the presence of flying seabirds. Bottom water temperature and anchovy density were key variables affecting the presence and density of penguins, while bottom water salinity was also important for penguin presence. Based on Akaike’s information criterion, the most important factor explaining the density of flying seabirds was the difference between surface and bottom salinity (ΔS), while for penguin density, the most important factor was anchovy density. These results highlight that the subtropical shelf front in the SW Atlantic Ocean is a key feature influencing the aggregation of flying seabirds and confirm the close association of penguins and anchovies. Bottom water intrusion, originating from the sub-Antarctic shelf water, is an important factor explaining the presence of penguins, which tend to aggregate in areas with high anchovy densities on the SW Atlantic continental shelf.

scholarly journals Long term fish assemblages as units of management in a temperate estuary (Rio de La Plata - SW Atlantic Ocean)

2011 ◽  
Vol 59 (1) ◽  
pp. 43-59 ◽  
Author(s):  
María Inés Lorenzo ◽  
Juan M. Díaz de Astarloa ◽  
Walter Norbis ◽  
María B Cousseau
Keyword(s):  
Continental Shelf ◽  
Fish Assemblages ◽  
Open Systems ◽  
Principal Component ◽  
Demersal Fish ◽  
Rio De La Plata ◽  
Environmental Characteristics ◽  
Río De La Plata ◽  
La Plata ◽  
Inner Continental Shelf

Demersal fish assemblages from trawl surveys in the Rio de la Plata estuary and its inner continental shelf were analyzed from 1975 to 1995. The first two factors of Principal Component Analysis explained 48% of the variance in species distribution, and they are consistent with the results of a cluster analysis. The analysis indicated the existence of three spatially and temporally distinct fish assemblages: internal and external estuarine and inner continental shelf (Uruguayan coastal assemblages). These assemblages were persistent considering the environmental characteristics and their species composition. Despite the changes registered in the species density during the period surveyed, the fish assemblages tend to persist over time. It was demonstrated that the assemblages can be considered as open systems and that there exists a reciprocal flow of organisms between adjacent associations. However, each assemblage showed high spatial and temporal persistence in accordance with the environmental characteristics of the system analyzed. Therefore, and according to the multispecies fisheries operating in the system, each assemblage defined could be considered a unit of management.

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