Chesterfield-Bellona Coral Reef Complex and Seamounts IMMA

Size in Square Kilometres

59,852 km2

Qualifying Species and Criteria

Humpback whale – Megaptera novaeangliae

Criterion A; B (ii); C (i, iii)

Marine Mammal Diversity 

Stenella longirostris; Tursiops aduncus

Summary

The Chesterfield-Bellona Coral Reef Complex and Seamounts IMMA constitutes a remote and vast region in the southwestern Pacific, with diversified marine habitats and very limited anthropogenic influence. This IMMA, located halfway between Australia and New Caledonia, includes two major plateaus surrounded by barrier reefs and islets, and three unsheltered shallow banks (La Boussole, Vauban and Dumont D’Urville). Further south, the IMMA includes several seamounts along the Lord Howe seamount chain (Nova, Argo, Kelso, Capel). The IMMA is for the most part located inside the Economic Exclusive Zone (EEZ) of New Caledonia and the Natural Park of the Coral Sea under the jurisdiction of the government of New Caledonia. As part of the park, a natural reserve (MPA IUCN category II) and an integral reserve (MPA IUCN category Ia) were created in 2018 over the Chesterfield-Bellona plateaus (Garrigue et al., 2020). Finally, a small portion at the southern extremity of the IMMA is located in international waters.

The Chesterfield-Bellona archipelago has been identified as one the two hotspots targeted by 19th century commercial whaling of humpback whales in the South Pacific (Townsend, 1935), which suggests that it historically hosted large numbers of humpback whales. Four scientific expeditions conducted in 2002, 2010 (Oremus and Garrigue, 2014), 2016 and 2017 (Garrigue et al., 2020) have confirmed that whales are still present in the area. The lagoons enclosed within the Chesterfield-Bellona plateaus and the shallow banks of La Boussole, Vauban and Dumont D’Urville, are likely to serve as breeding and nursing grounds based on observations of numerous females with calves (Garrigue et al., 2020). Niche modelling based on sightings recorded during research surveys supports the suitability of Chesterfield-Bellona habitats for humpback whales (Derville et al., 2018; Garrigue et al., 2020). Finally, recent deployment of satellite tags (2016-2017) showed that humpback whales intensively used the IMMA (Derville et al., 2020; Garrigue et al., 2020).

Connectivity was established with New Caledonia and the Australian Great Barrier Reef.  Movement of satellite-tracked whales and photo-ID matches further suggested that whales coming from the Chesterfield-Bellona archipelago could migrate south along the east Australian migratory corridor(Derville et al., 2020). Other marine mammal species observed in the area include the spinner dolphin (Stenella longirostris), the Indo-Pacific bottlenose dolphin (Tursiops aduncus) and unidentified Balaenoptera spp. The paucity of records for marine mammals other than humpback whales is likely due to the logistical difficulty to survey this remote region, rather than the reflection of true absence.

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

Recent multidisciplinary analyses combining satellite tracking, song analysis, photo-identification and genetics were conducted on humpback whales visiting the Chesterfield-Bellona plateaus in austral winter. The results did not allow to conclude to  the origin of this population but they demonstrated a connexion with the New Caledonia breeding sub-stock E2 classified as endangered in the IUCN red list (Childerhouse et al., 2008) and with the neighbouring Australian Great Barrier Reef breeding population (Chaplin, 2018; Derville et al., 2020; Garrigue et al., 2020, 2015, 2010). Expeditions conducted in the Chesterfield-Bellona plateaus during 2016 and 2017 provided the first evidence on connectivity between this vast area. The comparison of photo-ID and genotypes collected during the 2016 and 2017 expeditions with the New Caledonian catalogues of humpback whales revealed that 34 % of whales photo-identified during the expedition and 26 % of those genotyped had previously been observed in the “New Caledonia Main Lagoons and Shelf Waters IMMA” (Garrigue et al., 2020).  In addition, two satellite tracked whales travelled from The New Caledonian Southern Seamounts and Banks IMMAwhere they were tagged and finally followed a direct route to this remote area.

Criterion B: Distribution and Abundance

Sub-criterion Bii: Aggregations 

Research surveys conducted in the IMMA have recorded a relatively low density of humpback whales (0.041 whales.km-1) compared to what could be expected from the 19th century whaling data (Garrigue et al., 2020; Oremus and Garrigue, 2014). No aggregation of humpback whales has recently been recorded, but historical whaling data suggest that aggregations used to occur in the area (Townsend, 1935). No humpback whale was sighted on the Chesterfield plateau in 1992 (Gill et al., 1995) and very few were observed during two boat-based surveys conducted in 2002 and 2010 (Oremus and Garrigue, 2014). The Chesterfield-Bellona plateaus were more extensively surveyed in 2016 and 2017 during the “Marine Mammals of the Coral Sea” expeditions (MARACAS 1 and 3) and the highest densities of humpback whales were estimated over the offshore shallow banks (0.041 whales.km-1) separating the Chesterfield and Bellona plateaus. The encounter rate for the 2016-2017 surveys was estimated at 0.038 whales.km-1 for the Chesterfield plateau and 0.035 whales.km-1 for the Bellona plateau (Garrigue et al., 2020). Overall, the encounter rate was higher in 2017 (0.051 whales.km-1) than in 2016 (0.025 whales.km-1) suggesting some temporal variability in the numbers of humpback whales likely aggregating in the IMMA in each year.

Criterion C: Key Life Cycle Activities

Sub-criterion Ci: Reproductive Areas

Given recent behavioural observations, the area appears to be used as a nursing ground and could also serve as a mating and calving ground (Garrigue et al., 2020; Oremus and Garrigue, 2014). During the MARACAS 1 and 3 expeditions, 44 % of all the humpback whale groups encountered included mothers with a calf. Genetic analysis of samples collected in the area also revealed an unusual sex ratio largely skewed toward females (1:2.4). Although few competitive groups were observed, singing behaviour noted on multiple occasions during both expeditions attested to breeding activities (Chaplin, 2018; Garrigue et al., 2018, 2017).

Sub-criterion Ciii: Migration Routes

Although the IMMA is located under breeding latitudes for humpback whales, the area appears to also be used as a stop-over for longitudinal migrations during the austral winter. Using the Capel and Kelso seamounts as stepping stones, two males tagged in south-eastern New Caledonia crossed the Coral Sea to reach the East Australian coast south of the E1 Great Barrier Reef breeding grounds (Derville et al., 2020). Furthermore, whales tagged over the Chesterfield-Bellona plateaus stopped over the Capel and Kelso seamounts while initiating their southern migration (Derville et al., 2020). Satellite tracking therefore suggests that the seamounts located in the southern part of the IMMA are crossroads for humpback whales migrating through the Coral Sea.

Supporting Information

Chaplin, G., 2018. Population identity of humpback whales in the Chesterfield reef complex through song., Bachelor of Science (Honours). University of Queensland, School of Veterinary Science.

Childerhouse, S., Jackson, J., Baker, C.S., Gales, N., Clapham, P.J., Brownell Jr., R.L., 2008. Megaptera novaeangliae (Oceania subpopulation). The IUCN Red List of Threatened Species. Version 2009.2. www.iucnredlist.org.

Derville, S., Torres, L.G., Iovan, C., Garrigue, C., 2018. Finding the right fit: Comparative cetacean distribution models using multiple data sources and statistical approaches. Divers. Distrib. 24, 1657-1673. https://doi.org/doi:10.1111/ddi.12782

Derville, S., Torres, L.G., Zerbini, A.N., Oremus, M., Garrigue, C., 2020. Horizontal and vertical movements of humpback whales inform the use of critical pelagic habitats in the western South Pacific. Sci. Rep. 10, 4871. https://doi.org/10.1038/s41598-020-61771-z

Garrigue, C., Bonneville, C., Derville, S., Dodemont, R., Legendre, R., Oremus, M., Pérard, V., Williamson, M., 2018. Rapport des campagnes MARACAS 3, 4 & 5. Opération Cétacés & IRD, Noumea. https://doi.org/dx.doi.org/10.17600/17003700

Garrigue, C., Bonneville, C., Derville, S., Dodemont, R., Oremus, M., Pérard, V., 2017. Rapport des campagnes MARACAS 1 & 2. Opération Cétacés & IRD, Noumea.

Garrigue, C., Clapham, P.J., Geyer, Y., Kennedy, A.S., Zerbini, A.N., 2015. Satellite tracking reveals novel migratory patterns and the importance of seamounts for endangered south pacific humpback whales. R. Soc. Open Sci. 2. https://doi.org/10.1098/rsos.150489

Garrigue, C., Derville, S., Bonneville, C., Cheeseman, T., Baker, C.S., Millet, L., Paton, D., Steel, D., 2020. Searching for humpback whales in a historical whaling hotspot of the Coral Sea, South Pacific. Endanger. Species Res. https://doi.org/doi.org/10.3354/esr01038

Garrigue, C., Zerbini, A.N., Geyer, Y., Heide-Jørgensen, M.-P., Hanaoka, W., Clapham, P., 2010. Movements of satellite-monitored humpback whales from new caledonia. J. Mammal. 91. https://doi.org/10.1644/09-MAMM-A-033R.1.

Gill, P.C., Eyre, E.J., Garrigue, C., Dawbin, W.H., 1995. Observations of humpback whales (Megaptera novaeangliae) on a cruise to New Caledonia and the Chesterfield reefs. Mem. Queensl. Museum, 38, 505-511.

Oremus, M., Garrigue, C., 2014. Humpback whale surveys in the Chesterfield Archipelago: A reflection using 19th century whaling records. Mar. Mammal Sci. 30. https://doi.org/10.1111/mms.12080

Townsend, C.H., 1935. The distribution of certain whales as shown by logbook records of American whaleships. New York Zool. Soc. 19, 1–150, 4 charts.

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