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ISRA FACTSHEETS

AUSTRALIA AND SOUTHEAST INDIAN OCEAN

ISRA FACTSHEETS

AUSTRALIA AND SOUTHEAST INDIAN OCEAN

Sunday Bay ISRA

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Sunday Bay ISRA

Sunday Bay

Summary

Sunday Bay is located in western Shark Bay, Western Australia, Australia. This area sits between South Passage and Denham Sound in a shallow bay characterised by an intertidal limestone platform covered with oysters and sea urchins. The climate is semi-arid and during the austral summer this area is protected from the prevailing southwest winds. Within this area there are: undefined aggregations (Nervous Shark Carcharhinus cautus).

Sunday Bay

Sunday Bay

DESCRIPTION OF HABITAT

Sunday Bay is located in western Shark Bay, Western Australia, Australia. This area sits between South Passage and Denham Sound within a deep, narrow, high-energy channel bordered by rugged limestone cliffs and rocky shores. The benthic sediment is composed of turf rubble (Sutton & Shaw 2020). South Passage serves as one of the main conduits for oceanic water exchange between the open Indian Ocean and the semi-enclosed Shark Bay (Sutton & Shaw 2020). This area is a shallow bay characterised by an intertidal limestone platform covered with oysters and a mix of echinoderm species (E Gosden pers. obs. 2025). It also includes a sandy beach and seagrass meadows.

This area has a semi-arid climate characterised by two main seasons: warm to hot austral summers (October–March) and mild winters (April–September). The bay’s waters are warmer than adjacent oceanic waters in summer and cooler in winter (Nahas et al. 2005). Average sea surface temperatures are higher in summer (mean = 24.6 ± 1.0°C) than in winter (mean = 20.8 ± 1.7°C). The region experiences strong tidal currents and high-energy swell exposure. Water circulation is influenced by the Leeuwin Current, which brings warm, low-salinity tropical water southward, mixing with the bay’s hypersaline inner waters. During the summer, this area is protected from the prevailing southwest winds whereas in winter it is exposed to the eastern winds (E Gosden pers. obs. 2025). This area is sheltered from the swell and currents.

This area overlaps with Shark Bay Marine Park (WA DBCA 2025).

This Important Shark and Ray Area is benthic and pelagic and is delineated from inshore and surface waters (0 m) to 10 m based on the bathymetry of the area.

CRITERION C

SUB-CRITERION C5 – UNDEFINED AGGREGATIONS

Sunday Bay is an important area for undefined aggregations of one shark species.

Between 2022–2024, shore-based and aerial (using drones) observations indicated that Nervous Sharks occur regularly and predictably in this area. Between October–April, this area was visited 4–7 days per week for tourism activities (E Gosden pers. obs. 2025; Shark Bay Eco Tours unpubl. data 2022–2024). There was an estimated 90% chance of observing Nervous Sharks from the shoreline. A total of 64 aggregations were recorded from this area involving 4–200 individuals (average = 25) (Shark Bay Eco Tours unpubl. data 2022–2024). The size of sharks were visually estimated ranging from 30–100 cm total length (TL) with most individuals between 40–80 cm TL. Nervous Shark size-at-birth is 35–40 cm TL (Ebert et al. 2021) and young-of-the-year (YOY) are estimated as <60 cm TL (White et al. 2002). Size-at-maturity is between 85–101 cm TL for females and 80–91 cm TL for males (Ebert et al. 2021). Therefore, individuals recorded are most likely neonates, YOY, and juveniles. When bait balls of small prey species (e.g., hardyheads belonging to the family Atherinidae) are observed, sharks are feeding on them. Additional information is required to understand the nature and function of these aggregations.

Sunday Bay

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