Sharks, Rays and the Health of Moreton Bay

Healthy shark and ray populations are one of the clearest signs of a fully-functioning marine ecosystem. They help regulate food webs, connect habitats as they move through the seascape, and influence the structure, balance and abundance of marine life.

Moreton Bay is home to remarkable nature. For elasmobranchs — sharks and rays — it’s a globally significant gathering place for species such as mantas, leopard sharks and guitarfish. The Moreton Bay Foundation’s sedimentation synthesis identifies 44 shark species and 29 ray species occurring in the Bay and adjacent waters — an extraordinary diversity shaped by the Bay’s location, sitting at the crossroads of tropical and temperate marine zones, and by its range of habitats.

Sharks and rays rely on the Bay’s mosaic of clean water, productive seagrass meadows, mangroves, tidal flats, reefs, channels and nursery grounds. Eagle rays, wobbegongs, stingrays, shovelnose rays, hammerheads and even the occasional whale shark move through the Bay, connecting habitats and contributing to its ecological life. Sharks play a vital role in regulating fish populations and influencing the abundance and diversity of marine species, while rays play an important shaping the shallows, where their feeding pits create small pools that provide nursery habitat for young fish and prawns. Their presence matters, but they can only persist if the habitats that sustain them remain healthy.

Habitat health is where the Bay’s increasing sediment loads fit into the story. Sediment doesn’t just cloud the water after rain. When too much soil, silt and organic material is washed from the major catchments into the Bay, it reduces light reaching seagrass, smothers sensitive habitats, alters feeding grounds and affects species abundance.

For sharks and rays, those changes matter. They rely heavily on the Bay’s living infrastructure — the habitats that support their food, shelter, movement and reproduction. When sediment degrades those habitats, it weakens the systems that sustain them.

Sediment is not just a water-quality issue. It’s a habitat issue, a food-web issue, and ultimately a biodiversity issue. For sharks and rays, the health of Moreton Bay is written into the seagrass, sandflats, reefs, mangroves and nursery grounds they depend on. Protecting and maintaining those habitats is how we will protect the sharks, rays and the myriad other species that make Moreton Bay such a remarkable natural asset.

Further Reading here: Sharks and Rays: Sediment Impact Statement