Northeastern Brazil Antarctic Minke Whale Breeding Habitat IMMA

Criterion B: Distribution and Abundance

Sub-criterion B2: Aggregations

Ship based line transect surveys demonstrate that Antarctic minke whales (Balaenoptera bonaerensis) aggregate off the northeast coast of Brazil during the breeding season, increasing in number from winter to spring (Andriolo et al., 2010). Whaling data from the 1960s also confirm the seasonal occurrence of the species in the region from July to December, with a peak of catches of both males and females in October and November (Williamson, 1975, Lucena, 2006). Data from this period also revealed a relatively high density (6.57 whales per 100km2) in the whaling area (Lucena, 2006). More recent data from line transect ship surveys suggests that Antarctic minke whales are also regularly found to the north and to the south of the historical whaling ground, with a relatively high encounter rate (SR = 0.031 individuals/nm) (Andriolo et al., 2010).

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

The NE coast of Brazil has long been considered a breeding ground for Antarctic minke whales (Williamson, 1975). Examination of reproductive organs of whales caught in this area and processed in the whaling station of Costinha in the 1960s showed that both males and females were reproductively active off Brazil (Williamson, 1975; Lucena, 2006). More recently, Andriolo et al. (2010) reported a relatively high density of Antarctic minke whales in this area, with the observation of animals exhibiting mating behaviour. However, the number of calves recorded in this area was relatively low based on both whaling records (Williamson, 1975; Lucena, 2006) and ship surveys (Andriolo et al., 2010). These findings strongly suggest that this region is an important mating ground for the species and that females give birth in a different area (Lucena, 2006; Andriolo et al., 2010). Finally, western South Atlantic humpback whales (Megaptera novaeangliae) are found in this region in relatively high densities (Fig. 2). Ship-based line transect surveys conducted in the early 2000s estimated the number of humpback whales inhabiting this region in the winter/spring to be around 600 individuals (Zerbini et al., 2004). The presence of females with calves suggests that this region is used as a calving ground for the species (Zerbini et al., 2004).

Criterion D: Special Attributes

Sub-criterion D1: Distinctiveness

The Northeast Brazil breeding habitat of Antarctic minke whales represents the only known breeding ground of the species in low latitude waters. Minke whales were heavily exploited in the Antarctic, but lower latitude areas of concentration are only known off NE Brazil and near Durban in South Africa (Horwood, 1990). In NE Brazil, a large percentage of males and females caught by whaling operations in the early 1970s were mature (100% of males and 90% of females) and reproductively active (Williamson, 1975). Immature animals were seen (but not taken) in a relatively smaller proportion, primarily early in the season. In Durban the catches consisted of a mix of mature and immature animals, and the proportion of sexually active whales was much smaller (Williamson, 1975).  As such the waters of this IMMA are exceptional as they are the principal known mating ground for this species.

Sub-criterion D2: Diversity

In addition to Antarctic minke whale, four other large whale species have been documented in this region, including Bryde’s whale (Balaenoptera edeni), sei whale (B. borealis), sperm whale (Physeter macrocephalus) (Andriolo et al., 2010) and humpback whale (Megaptera novaeangliae) (Zerbini et al., 2004). This relatively high diversity indicates this is a suitable habitat for several migratory whale species during their breeding season in low latitudes. All of these species were caught offshore of Costinha during the whaling period (Williamson, 1975; Andriolo et al., 2010) in relatively large numbers, suggesting that they were relatively abundant at the onset of commercial whaling in the region. Moreover, iat least three offshore delphinids have been regularly recorded in these deep waters in more recent ship surveys:  Pantropical spotted dolphins (Stenella attenuata), Clymene´s dolphins (S. clymene) and spinner dolphins (S. longirostris) (Moreno et al., 2005).