The Southern Seamounts and Banks of New Caledonia IMMA includes some of the primary reproductive areas of the breeding sub-stock of humpback whales designated by IWC as E2 and considered as endangered by IUCN. Whales specifically concentrate around these offshore shallow structures where they come for breeding and nursing during austral winter. High densities have been recorded in the vicinity of the seamounts, especially near Torche bank, Orme bank, and Antigonia seamount. Both residence time and behaviour suggest the seamounts are critical habitat for this endangered population.
Description of Qualifying Criteria
Criterion A – Species or Population Vulnerability
The group of humpback whales migrating to New Caledonia belongs to the Oceania subpopulation which is classified as endangered by IUCN (Childerhouse et al 2009). Humpback whales show a high fidelity to the area, and photo-ID and genetics demonstrate that there are also strong connections between this IMMA and the “New Caledonia main island lagoons IMMA”. Humpback whales were observed in high number during the four surveys undertaken on the Southern Seamounts with an encounter rate ranging between 0.11 to 0.39 whales/km (Garrigue et al 2017b). At least 400 individual whales were identified through photo-ID over a three-year period (233 from the Southern Lagoon IMMA, 126 from Southern Seamounts IMMA, 41 matched from both areas) and analysis showed that humpback whales were almost equally likely to return to either (Southern seamounts or main islands lagoon) area in successive years. Indices of intra-annual exchanges indicates that whales were more likely to travel between the areas in the same year than to return to the same area in a different year (Garrigue et al 2013).
Criterion B: Distribution and Abundance
Sub-criterion Bii: Aggregations
The IMMA constitutes aggregation spots for humpback whales within the reproductive breeding grounds of New Caledonia (Garrigue et al. 2015, 2017). They were observed in high number during the four surveys undertaken on the Southern Seamounts with an encounter rate ranging between 0.11 to 0.39 whales/km (Garrigue et al. 2017b). A switching state-space model (SSSM) using a correlation random walk model showed that whales demonstrate a behaviour qualified as “area-restricted search (ARS)” on Antigonia and La Torche which could be indicative of foraging but also of resting or breeding (Garrigue et al. 2015). SSSM and occupancy time indicate significant use of the IMMA by whales (Garrigue et al. 2015). Behavioural observations during surveys suggest that whales are aggregating within the IMMA for reproduction.
Criterion C: Key Life Cycle Activities
Sub-criterion Ci: Reproductive Areas
The Southern seamounts of New Caledonia have been identified as a reproductive area based on field-based observation (Garrigue et al. 2011, Derville et al. 2016). The area is used for mating and nursing, and also likely for calving, and it constitutes one of the major breeding grounds for this sub-stock. Boat-based data collected between 1996 and 2017 showed that the proportion of groups with calves was higher in the Southern Seamounts (27%) than in the South Lagoon (16%).
Criterion D: Special Attributes
Sub-criterion Di: Distinctiveness
New Caledonian humpback whales are the reproductive sub-stock E2 as named by IWC, which is genetically different to the other sub-stocks identified in the South Pacific Ocean (Olavarria et al. 2007). The Southern seamounts includes one of the only known breeding areas for humpback whales located in a purely offshore unsheltered oceanic environment (i.e. no emerged reef structures or land) (Garrigue et al. 2017a). MtDNA of 1112 samples collected over the south Pacific (New Caledonia, Tonga, Cook Islands, French Polynesia, Colombia) and Western Australia revealed 115 unique haplotypes. Significant differentiation, at both the haplotype and nucleotide level (FST = 0.033; ΦST = 0.022), were found among the 6 breeding grounds and for most pair-wise comparisons (Olavarria et al. 2007).
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