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Anales Instituto Patagonia (Chile) v.36 n.2 Punta Arenas 2008
Anales Instituto Patagonia (Chile), 2008. 36(2):69-74
SOUTH-WEST ATLANTIC RIGHT WHALES EUBALAENA AUSTRALIS (DESMOULINS, 1822) DISTRIBUTION NEARBY THE MAGELLAN STRAIT
DISTRIBUCIÓN DE LA BALLENA FRANCA EUBALAENA AUSTRALIS (DESMOULINS, 1822) DEL ATLÁNTICO SUROCCIDENTAL CERCA DEL ESTRECHO DE MAGALLANES
Jimena BelgranoI, Miguel IñíguezI,II, Jorge GibbonsIII,IV, Cristian GarcíaIII & Carlos OlavarríaIV
I Fundación Cethus. Potosí 2087, Olivos, Buenos Aires, Argentina, firstname.lastname@example.org, email@example.com
Southern right whales Eubalaena australis (Desmoulins, 1822)1 formerly occurred in very large numbers in the Southern Hemisphere, particularly in coastal waters of the southern part of Australia, New Zealand, American and African continents, as well as in most of the islands between 30°S and 60°S (Townsend 1935, Matthews 1938, Dakin 1963). It has been estimated that by the beginning of its exploitation (late XVIII century), there were between 60,000 and 160,000 individuals. However, severe depletion of this species by commercial whaling may have reached as low as 200-300 individuals by 1920 (Anonymous 2001, Jackson et al. 2007).
Off both Pacific and Atlantic coast of South America southern right whales were caught extensively (Townsend 1935). Historical whaling accounts from Chile referred to a well known catching ground called the "Coast of Chile Ground". This stock of whales seems have been distributed between 30°S and 50°S (Townsend 1935). Based on the logbooks of Yankee and French whalers, and on Chilean whaling catch data it has been estimated that around 9,000 individuals were hunted there between 1785 and 1976 (Aguayo-Lobo et al. submitted2). Along the Atlantic coast of South America, southern right whales were caught off southern Brazil, and along Uruguay and Argentina coasts south to Tierra del Fuego, with a large proportion of whales obtained offshore in the so called "Brazil" and "False" banks (Townsend 1935). It is estimated that 29,568 southern right whales were caught in the Brazil bank between 1772 and 1812 (Richards 1994).
Unlike in the South-East Pacific, where a slow recovery of the southern right whales population has been supported by the increasing number of sightings and extended distribution north up to Perú (Aguayo-Lobo & Torres 1986, Aguayo-Lobo et al. 1992, Van Waerebeek et al. 1992, Van Waerebeek et al. 1998, Santillán et al. 2004, Olavarría et al. 20053, Aguayo-Lobo et al. submitted), in the South-West Atlantic it has been documented a steady recovery, particularly for Península Valdés, Argentina (Payne et al. 1990, Cooke et al. 2001), but also for Brazil (Castello & Pinedo 1979, de Oliveira Santos et al. 2001, Groch et al. 2005) and Uruguay (Piedra et al. 2006, Costa et al. 2007). Southern right whales have been recorded particularly in the southern part of Argentina (Santa Cruz province) (Goodall & Galeazzi 1986, Pérez et al. 1995, Tossenberger et al. 20004, Iñíguez et al. 20035, Belgrano et al. 20086), where some whales have been observed entering the Chilean Magellan Strait waters. Gibbons et al. (2006) analyzed contemporary sighting and stranding data of this species in the southern Chilean fjords finding that it only distributes at the central and eastern parts of the Magellan Strait and Beagle channel. Given the closest proximity to the range of the South Atlantic population, these whales were assumed to correspond with that population rather than with the South-East Pacific off Chile-Perú.
In this note we review the distribution of southern right whales in the area nearby the eastern entrance to the Magellan Strait, considering records from the nearby province of Santa Cruz, Argentina (Iñíguez et al. 2003) and the southern Chilean fjords (Gibbons et al. 2006), additionally to unreported records in both areas, with the aim of examining the local distribution of the species across the border between Argentina and Chilean waters.
In the area of Santa Cruz, Argentina, sightings have been recorded since 1986. We include here those records nearby Cabo Vírgenes and Punta Dungeness as in Iñíguez et al. (2003), as well as new records from further research undertaken in the area by Fundación Cethus since 2004. In the Chilean Patagonian and Fuegian channels and fjords, extensive surveys for cetaceans have been undertaken between 1997 and 2005 as in Gibbons et al. (2006). Further surveys have been undertaken by the Centre for Quaternary Research (CEQUA) in the fjords and channels at the central and western portions of the Magellan Strait, as well as in southern channels between 2003 and 2008.
Sixty-nine sightings of southern right whales have been recorded in the study area from 1985 and every year of the last nine years (Fig. 1, Table 1). Most of them have been concentrated in the Cabo Vírgenes area, with fewer in Punta Dungeness and in the central and eastern portions of the Magellan Strait. Most of the sightings were recorded during January, February and April, however this may be correlated to the greater sighting effort occurred in these months (data not shown).
The available data supports that the area nearby the eastern entrance of the Magellan Strait, including Cabo Vírgenes and Punta Dungeness, is used by southern right whales in recent times, similar to what occurred during early stages of commercial whaling by the distribution of Yankee whalers catches in the surrounding area (Townsend 1935). The apparent increasing in sightings from 90's decade might reflect the steady recovery of the South Atlantic population (Payne et al. 1990, Cooke et al. 2001), given that the eastern area of the Magellan Strait was extensively surveyed by experienced researchers searching for Commerson's dolphins that did not observed southern right whales there (Venegas & Atalah 1987, Leatherwood et al. 1988, Venegas 1996, Lescrauwaet et al. 2000).
From a local management perspective, in Chile two distinct management units should be considered when evaluating southern right whales, the Chile-Perú stock distributed off Pacific coast and the South Atlantic stock that distributes along the Magellan Strait and the Beagle Channel. This has not been clear in the past as a small portion of whales reported for Chile were in fact caught nearby the South-West Atlantic south of Tierra del Fuego and near the eastern entrance of the Magellan Strait, likely including whales from that ocean basin and incorrectly assigning them to the South-East Pacific Chile-Perú stock. Despite extensive effort in western areas of Magellan Strait and Patagonian and Fueguian channels, no southern right whales have been observed there (Gibbons et al. 2006, Jorge Acevedo, comm. pers., CEQUA unpublished data), supporting the hypothesis that the whales observed in the eastern part of the Magellan Strait correspond to the South Atlantic population (Gibbons et al. 2006). Moreover, the hiatus in the distribution across southern South America makes likely a reduced demographic interchange between both South-East Pacific and South Atlantic populations.
The study area seems to have a high potential for commercial activities related to whale watching on southern right whales from shore as it occurs in several locations along the south Atlantic coast of South America, notably Península Valdés (Hoyt & Iñíguez 2008). Moreover, in Chile this is the location with more potential for this type of activity given the presence of the species is relatively regular. However, for a fully development of whale watching several biological and ecological aspects, such as habitat use at small scale and seasonal distribution patterns should be studied. Further systematic surveys are possible to undertake from the shore nearby Punta Dungeness, where Chilean Navy personnel from the lighthouse as well as "estancias" farmers report that they regularly observe whales from the shore. A coordinated systematic survey at Cabo Vírgenes will provide a more complete understanding of the southern right whales at the eastern entrance of the Magellan Strait.
In Argentina we thank Prefectura Naval Argentina and Cristian de Haro for assistance in the field and providing information. JB and MI were financially supported by the Whale and Dolphin Conservation Society (United Kingdom), Cetacean Society International (USA) and the Humane Society of the United States (USA). Petrobras Energía also financially supported JB. Fundación Cethus research was undertaken under permits issued by the Subsecretaría de Medio Ambiente and the Dirección de Recursos Naturales, Consejo Agrario Provincial, Provincia de Santa Cruz, Argentina. In Chile we thank Jorge Acevedo for providing the information on CEQUA surveys. The work of JG in Chile was partially supported by grants from the "Acción Integrada Universidad Complutense de Madrid - Universidad de Magallanes", FONDEMA Código BIP 30059585-0 and FONDECYT 1020004. We are grateful to Jaime Cárcamo, José Zamorano and Fernando López Mirones for fieldwork assistance.
1 The taxonomy of right whales has been discussed in recent years. Rice (1998) proposed all right whales species plus the bowhead belonged to the genus Balaena Linnaeus, 1758. However, genetic evidence supported the earlier separation retaining the scientific name Eubaíaena austraíis (Desmoulins, 1822) for the southern hemisphere right whale (Rosembaum et al. 2000).
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Received: Sept., 12, 2008
Accepted: Nov., 25, 2008