Occurrence of Sei Whales (Balaenoptera borealis) in the Magellan Strait from 2004-2015, Chile

Discovering sounds in Patagonia: characterizing sei whale (<i>Balaenoptera borealis</i>) downsweeps in the south-eastern Pacific Ocean

“…Genetic and morphological analysis confirmed that the examined animals were sei whales (Häussermann et al, 2017). These historical sightings support the hypothesis of Guzmán (2006) about the presence of sei whales feeding in Chilean Patagonia between Chiloé Island and the Magellan Strait (Acevedo et al, 2017).…”

“…However, low-frequency sei whale downsweeps may have a different function from the stereotyped humpback vocalizations considered as songs (Edds-Walton, 1997). Though the behaviour of sei whales is poorly studied, most studies on this species state that sei whales prefer offshore waters, but these new records and sightings along the coast of Penas and Tres Montes gulfs (Aguayo-Lobo, 1974;Pastene and Schimada, 1999;Häussermann et al, 2017) demonstrated a wide habitat range, with the whales probably following productive feeding areas. If this is true, it is reasonable to assume that the calls of sei whale are influenced by the feeding conditions (as proposed by Baumgartner and Fratantoni, 2008) and have communicative functions, e.g.…”

“…Population boundaries and migratory patterns are also poorly understood. In the austral summer there are concentrations of sei whales between 40 and 50 • S; older, larger individuals tend to travel to the northern Antarctic, while smaller, younger individuals tend to stay at lower latitudes (Rice, 1998;Acevedo et al, 2017).…”

“…Between 1929 and 1983, sei whale captures represented 17.3 % of the total catch of whales in Chile. It was the third most hunted species, with approximately 1664 individuals captured principally on the north and central coasts (Aguayo-Lobo, 1974;Aguayo-Lobo et al, 1998), although these include an unknown number of Bryde's whales (Valdivia et al, 1981;Gallardo et al, 1983;Aguayo-Lobo et al, 1998). After the whale-hunting moratorium imposed by the International Whaling Commission in 1980, several research projects focused on the populations and recovery status of large whales such as right whales, humpback whales, blue whale, and fin whales (Reeves et al, 2002).…”

“…In Chile, there are opportunistic sightings and strandings of sei whales from Antofagasta (in the north) to the Magellan Straight (in the south), including the islands of Juan Fernandez (Gallardo et al, 1983;Schlatter, 1987;Aguayo-Lobo et al, 1998;Findlay et al, 1998;Pastene and Shimada, 1999;Guzmán, 2006;Acevedo et al, 2017). Many sightings in Central Chile and northern Patagonia (33-48 • S) have been reported since 1966, when 286 whales were sighted in March of 1966 (between 43 and 45 • S) and 114 in October of the same year (between 46 and 48 • S), all between 30 and 190 km off the shore (Aguayo-Lobo, 1974). In March 1968 Japanese whalers reported the sightings of several hundreds of sei whales between 46 • 40 and 48 • S, with a peak concentration 30 km off the coast of the Tres Montes Peninsula at the northern limit of the Penas Gulf (Pastene and Schimada, 1999).…”