The eastern South Pacific humpback whale population winters primarily off Colombia and Ecuador, extending northward to the coasts of Panama and Costa Rica. It migrates south to the Fueguian Archipelago and Antarctic Peninsula waters for feeding during the austral summer. In recent years, however, humpback whales have also been observed feeding in the Corcovado Gulf, in the northern Chilean Patagonian channels, during the austral summer and fall. We examine photographically identified humpback whales in order to determine interchange or isolation of these aggregations. The apparent absence of movements of identified humpback whales among the 3 summering areas, and the differences in the proportion of white/black coloration on the fluke, suggest that each locality corresponds to a discrete feeding area for eastern South Pacific humpback whales.KEY WORDS: Humpback whale · Eastern South Pacific · Corcovado Gulf · Fueguian Archipelago · Southern Ocean · Feeding ground
Resale or republication not permitted without written consent of the publisherEndang Species Res 22: 33-38, 2013 ado Gulf (43°53' S). Corcovado Gulf is located 1080 km north of the Magellan Strait, suggesting that this corresponds to another discrete feeding area for this population (Haro 2009, Hucke-Gaete et al. 2013). An alternative interpretation would be that the Corcovado Gulf may correspond to a transitory area during the whales' migration further south to the Fueguian Archipelago or the Antarctic Peninsula. Here we examine the relationship between photographically identified humpback whales in order to determine the degree of interchange or isolation among these 3 summer aggregations. Such information on possible sub-structuring of the population and stock identity is required to ensure appropriate use of capture-recapture models for reliable estimation of population size in the ESP, and to resolve central questions on one of the least understood humpback whale populations.
MATERIALS AND METHODSIndividual humpback whales were identified from photographs, based on unique pigmentation patterns and/or permanent scars on the ventral side and marks on the trailing edge of the fluke (Katona et al. 1979). Only medium-to high-quality fluke photographs were used in the comparisons, based on focus, angle, clarity, contrast, and recognition (distinctive patterns, marks, or scars) (Mizroch et al. 1990, Friday et al. 2000. Six photo-identification catalogs were used, covering 3 relevant localities: Corcovado Gulf (CG), Fueguian Archipelago (FA), and Antarctic Peninsula (AP). In addition, some identified whales from Wide Channel (49°50' S) to Smyth Channel (52°44' S), north of Magellan Strait, were included as part of the FA region. The surveyed areas are described in Table 1 The only abundance estimate for this population on feeding grounds was obtained for the Bransfield Strait area, with a derived abundance of 865 individuals (95% CI = 656 to 1141). However, this represents only a fraction of the AP feeding unit (Secchi et al. 2011). Populati...
