Bertarelli-Annual-Report-2024-LR - Flipbook - Page 43
Our Impacts in 2023
0
2.5
Marine Science 2023
5km
5.42°S
Peros Banhos
Channel
41
Figure 2. Peros Banhos Channel ISRA covers
36.4 km2 with depths between 0-280 metres.
The habitat within the area includes fringing
coral reefs, a lagoon, patch reef, seagrass beds
and oceanic areas on the southern side. This
area is designated due to the presence of and
undefined aggregations of grey reef shark.
5.47°S
Indian
Ocean
71.82°E
71.88°E
Indian
Ocean
6.64°S
Egmont
Atoll
Figure 3. Egmont Atoll ISRA is the largest
designated ISRA in the Chagos Archipelago,
it covers 133.19 km2 and reaches depths of 711
metres. It is a small reef atoll with an interior
lagoon system and comprises of multiple
habitats including sandy and rocky shores, sandy
substrates, coral reefs and pelagic waters. This
area is designated due to the presence of, feeding
areas of and undefined aggregations of reef
manta ray.
6.71°S
0
2.5
5km
71.32°E
71.39°E
The Egmont Atoll ISRA (figure 3) and Salomon Atoll
ISRA (figure 1) cover similar size areas of ~130 km2 for
reef manta rays whilst the Peros Banhos Channel ISRA
(figure 2) covers 36.4 km2 for the grey reef shark.
Using an array of acoustic receivers across the Chagos
Archipelago, data collected between 2013-2021 from grey
reef sharks with acoustic tags identified aggregations
of these sharks within the Peros Banhos Channel. These
aggregations occurred from March to December with
results suggesting larger aggregations occur in the area,
however the size and nature of these are not known.
These data combined with the classification of grey reef
sharks as Endangered allowed for the delineation of an
area meeting the ISRA criteria (figure 2).
The acoustic receiver array also detected tagged
reef manta rays, with high activity in Salomon Atoll.
Combined with observations of their feeding at the
channel mouth in Salomon Atoll, this site represents
an important foraging ground and frequently attracts
aggregations when conditions are suitable. More recent
data also highlight the importance of Egmont Atoll as
a feeding area, aggregation site and the location of at
least three cleaning stations for reef manta rays. With
their classification as ‘Vulnerable’ species, combined
with telemetry data, this provided sufficient evidence to
designate two separate sites as ISRAs (figure 1 and 3).
The designation of these ISRAs supports continued and
increased levels of protection and helps to refine our
spatial mapping of the most significant locations for
these threatened species within the archipelago.
References: IUCN SSC Shark Specialist Group (2023) Egmont Atoll ISRA Factsheet. Dubai: IUCN SSC Shark Specialist Group.
IUCN SSC Shark Specialist Group (2023) Peros Banhos Channel ISRA Factsheet. Dubai: IUCN SSC Shark Specialist Group.
IUCN SSC Shark Specialist Group (2023) Salomon Atoll ISRA Factsheet. Dubai: IUCN SSC Shark Specialist Group.
