Marine mammal occurrence in deep waters of the Brazil-Malvinas confluence off Argentina during summer

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This article presents the results of a summer survey of marine mammal occurrence at the Brazil-Malvinas Confluence in the Argentine Sea shelf break. A total of 61 marine mammal sightings were recorded. The most frequent species recorded were South American fur seals (Arctocephalus australis; 75.4%; 78–4670 m), followed by sperm whales (Physeter macrocephalus; 8.2%; 478–2825 m), sei whales (Balaenoptera borealis; 4.9%; 1513–4674 m) and long-finned pilot whales (Globicephala melas; 3.3%; 1119–1534 m), with a small number of unidentified cetaceans (4.9%; 87–2248 m). This new information about marine mammal species in the Brazil-Malvinas Confluence updates knowledge of their distribution in this highly productive area.


Ocorrência de mamíferos marinhos no verão austral em águas profundas da Convergência Subtropical no Atlântico Sul Ocidental, Argentina. Este artigo apresenta os resultados de registros de mamíferos marinhos obtidos durante um embarque na região sob influência da zona de Convergência Brasil-Malvinas na quebra da plataforma do Mar Argentino durante o verão austral. Foi obtido um total de 61 avistamentos. As espécies mais comuns foi lobo-marinho-sul-americano (Arctocephalus australis, 75.4%; 78–4670 m), cachalote (Physeter macrocephalus, 8.2%; 478–2825 m), baleia-sei (Balaenoptera borealis; 4.9%; 1513–4674 m) e baleia-piloto (Globicephala melas, 3.3%; 1119–1534 m). A presente informação contribui para uma melhor compreensão sobre a ocorrência de mamíferos marinhos em uma área altamente produtiva que é a Convergência Brasil-Malvinas.

La presencia del delfín listado, Stenella coeruleoalba (Meyen, 1833), en el Mar Argentino

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El conocimiento del género Stenella en el Atlántico Sudoccidental ha sido muy limitado. A pesar que el holotipo fuera capturado por Meyen (1833) en el estuario del Río de la Plata, solo unos pocos especímenes se registraron en el sector durante las últimas décadas. El presente estudio analiza la distribución y ocurrencia de delfines listados en el Mar Argentino, y sintetiza el conocimiento sobre su presencia en el Atlántico Sudoccidental. Stenella coeruleoalba se registra entre los 7° y 42° S, aunque la mayoría de los ejemplares se hallaron entre los 30° y 40° S. Cerca del 70% de los ejemplares hallados correspondieron a varamientos solitarios y, en todos los casos en que pudo determinarse el sexo, correspondieron a machos subadultos o adultos (205–242 cm). Un total de 10 cráneos se encuentran depositados actualmente en museos de Brasil, Uruguay y Argentina (LCB 402–471 mm). Los avistajes predominaron entre fines de primavera y verano (octubre–febrero), comprendiendo grupos reducidos (1–4 delfines) en aguas relativamente poco profundas (30–100 m). Un único ejemplar de esta especie fue capturado incidentalmente en operaciones de pesca de anchoíta en el norte de Patagonia y asociado con delfines comunes. Los patrones de coloración observados fueron el gris azulado en ejemplares varados y pardusco en ejemplares avistados, con la combinación característica de bandas laterales y la mancha dorsal. La corriente cálida del Brasil podría estar influenciando la presencia de delfines listados en Uruguay y Argentina durante el verano, a pesar que algunos de los ejemplares fueron registrados en aguas de temperaturas inferiores a los 20° C, las cuales están influenciadas por la Corriente de Malvinas. Las investigaciones futuras deberían focalizarse en la relación entre las condiciones ambientales y la distribución del género Stenella en el Atlántico Sudoccidental.


The presence of striped dolphins, Stenella coeruleoalba (Meyen,1833), in the Argentine Sea. The knowledge about the presence of striped dolphins (Stenella coeruleoalba) in the South Western Atlantic Ocean (SWAO) is very limited. Although the holotype was captured by Meyen (1833) in the La Plata River Estuary, only a few museum specimens and isolated strandings were recorded in the area. This study presents the distribution and occurrence of striped dolphins in the Argentine Sea and reviews its presence in the SWAO. S. coeruleoalba is found from 7° to 42° S, although most of the sixteen records were found between 30° and 40° S. Seventy percent of the dolphins were single stranded animals, and in the cases that sex was determined, all of them were juvenile to adult males (205–242 cm). A total amount of 10 skulls are deposited in museum collections of Brazil, Uruguay and Argentina (CBL 402–471 mm). The sightings were concentrated in late spring and summer (October–February), comprising small groups (1–4 dolphins) in relatively shallow water (30–100 m). Only a single incidental catch was recorded, being a dolphin associated with common dolphins feeding on anchovies in northern Patagonia. The colour pattern found was bluish grey in stranded animals and brownish in live dolphins, with the characteristic combination of lateral stripes and spinal blaze. The southbound warm Brazil Current may influence in the presence of striped dolphins in Uruguay and Argentina during austral summer, even though some animals were found during winter in waters of temperatures below 20° C clearly associated with the northbound cold Malvinas-Falkland Current. Future research should focus on the relationship between the environmental conditions and the distribution of the genus Stenella in the South Western Atlantic.