**3. Krill-eating baleen whale species in the Indo-Pacific sector of the Antarctic**

Baleen whale species, except the Bryde's whale, migrate seasonally between low latitude breeding areas in winter to high latitude feeding areas in the Antarctic in summer. The main prey species of baleen whales such as Antarctic blue, fin, humpback and Antarctic minke (*B. bonaerensis*) whales (**Figure 2**) is the Antarctic krill. Therefore the summer migrations of these whales to the Antarctic are related to areas of krill concentrations, which in turn are associated with gyral systems.

#### **3.1 Antarctic blue whale**

This is the largest baleen whale species. The record for a whale killed in the Southern Hemisphere in the first half of the past century was a body length of more than 30 m and weigh of nearly 180 tons. During the austral summer Antarctic blue whales are distributed between the AC and the ice edge. There is limited information on the population structure of this species.

#### **3.2 Fin whale**

This is the second largest baleen whale species, with a maximum length of more than 27 m and weight of nearly 120 tons. During the austral summer, fin whales are found extensively south of 50°S, but most commonly north of 60°S. There is limited information on the population structure of this species.

#### **3.3 Humpback whale**

This species presents a maximum body length of 17 m and weight of 40 tons. During the austral summer humpback whales are distributed from south of the AC to the ice edge, but just to the north of the main distribution area for Antarctic minke whale. The IWC has identified seven populations of humpback whales in the Southern Hemisphere, which are denominated with alphabetic letters from 'A' to 'G' [7]. The populations occurring in the Indo-Pacific sector of the Antarctic are Populations 'C' (mainly in Area III), 'D' (mainly in Area IV), 'E' (mainly in Area V), and 'F'

#### **Figure 2.**

*Krill-eating baleen whale species in the Indo-Pacific sector of the Antarctic. Top left: humpback whale; top right: Antarctic minke whale; bottom left: fin whale; bottom right: Antarctic blue whale.*

(mainly in Area VI) (**Figure 1**). There are some spatial overlaps between adjacent populations in the Antarctic [8]. The breeding areas for Populations 'D' and 'E' are located in West and East Australia, respectively.

#### **3.4 Antarctic minke whale**

This is one of the smallest baleen whale species with a maximum body length of more than 10 m and weight of nearly 10 tons. During the austral summer, Antarctic minke whales are distributed mainly around the pack-ice. There are at least two populations of this species in the Indo-Pacific sector of the Antarctic, the Eastern Indian Ocean population in the western part of the research area (mainly the eastern part of Area III and Area IV) (**Figure 1**), and the Western South Pacific population in the eastern part of the research area (mainly the eastern part of Area V and Area VI) (**Figure 1**) [9, 10]. Both populations interact in a transition area between approximately 100° and 160°E (eastern part of Area IV and western part of Area V) (**Figure 1**) [11].

The biological and demographic studies summarized below are based on the approximate geographic limits of these 'populations' in the case of humpback and Antarctic minke whales, and on geographical areas for those species with limited information on population structure (Antarctic blue and fin whales).
