Presence of blue whale ( Balaenoptera musculus ) in the northwestern coast of Chiloé Island, southern Chile

Although some populations of blue whales (Balaenoptera musculus) appear to be increasing after gaining legal protection from commercial whaling in 1966 (NMFS, 1998), others are not (Clapham et al., 1999). In the Southern Hemisphere alone, more than 350,000 blue whales were taken by whaling fleets from 1904 to 1967 and thousands more were killed, but not reported, by Soviet whaling fleets in the 1960s and 1970s (Reeves et al., 2003). In Chile, commercial whaling started at the end of the 18th century and by 1900 Punta Arenas (Region XII), Chiloé and Valdivia (Region X) had become important whaling stations. Historical records of blue whales in Chile describe a former whaling area around Chiloé Island and the Corcovado Gulf (Aguayo-Lobo et al . , 1998), approximately between 41°15’S and 43°30’S. In 2003, the western side of Chiloé Island and the Corcovado Gulf were identified as one of the most important blue whale feeding and nursing grounds discovered to date in the Southern Hemisphere (Hucke-Gaete et al., 2004). Here we present recent records of blue whales made in the northwestern region of Chiloé Island, between 41°45’S and 42°15’S, that complement those observations reported by Hucke-Gaete et al. (2004) and are among the first in this area since the end of commercial whaling operations in Chilean waters. The research work was developed under the Southern Right Whale Project/Chile that the Cetacean Conservation Center (CCC) has been carrying out since February 2003 in order to investigate the presence of great whales in the northern Chiloé Island. Between 16 February and 17 March 2004, weather permitt ing, CCC developed land-based observations, two marine surveys on board fishermen vessels and one aerial survey on board a Chilean Marine Navy aircraft. Trained observers working from land-based platforms located at a height of 38m and 58m above sea level, and using 12x50 binoculars, conducted 29 days of observations lasting on average 6.6 h (SD = 3.3h) during daylight hours of 08:00 – 20:30. With 190.9 h of land-based effort, balaenopterids were observed and identified during al l days. The maximum number of balaenopterids sighted daily varied from 2 to 19 individuals, with an average of 9.03 (SD = 4.7) whales per day. On six occasions and from different observation platforms, the whales were positively identified as B. musculus (Figure 1, Table 1). When whales were sighted from land-based platforms, observers estimated the distance of the whales to the coast (Table 1) and the reported location refers to the geographic coordinates of the platform. When whales were sighted from marine or aerial platforms, the distance of the whale(s) to the coast was calculated using GPS coordinates and in these cases, the location refers to the actual position of the whale. The near proximity of deep water to cliff-based sighting stations allowed the documentation of feeding behavior and defecation from land as well as during marine surveys. The presence of blue whales and the observations of defecation in the northwestern area of Chiloé Island suggest that the feeding and nursing ground identified