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Winter plunges in the sea may come as a surprise with warmer temperatures, especially off the coast of Sydney, where tropical coral trout are being caught. This phenomenon can be attributed to the increasing heat in the oceans, as they absorb most of the additional heat trapped by greenhouse gases such as carbon dioxide. Oceanic heat build-up has been rapidly increasing, despite the absence of El Niño. The forecast suggests that coastal waters will be significantly warmer than usual in the coming months, up to 2.5℃ warmer in various areas. This increase in temperature forces many marine species to move or face the risk of extinction. Consequently, species that have the ability to relocate are already doing so. In Australia alone, around 200 marine species have shifted their distributions since 2003, with 87% moving towards the south. This migration trend is evident worldwide, both on land and in the ocean. Due to the warmer ocean temperatures this year, Australia’s marine environments are projected to resemble summer rather than winter. So, the next time you engage in activities such as fishing, diving, or beachcombing, remain alert and prepare your camera. You might witness firsthand the great upheaval happening beneath the surface. Here are eight species that are on the move:
1. Moorish idol (Zanclus cornutus)
Historic range: Northern Australia
Now: This spectacular fish can now be found as south as Geraldton in Western Australia and Eden in New South Wales. Divers will be delighted to spot this fish among hard-bottomed habitats.
2. Branching coral (Pocillopora aliciae)
Historic range: Northern New South Wales
Now: This beautiful pale pink coral can be spotted south of Port Stephens, near Sydney. Even seemingly immovable species like coral are fleeing from the heat. They are already providing homes for various other migratory species such as tropical fish and crabs.
3. Eastern rock lobster (Sagmariasus verreauxi)
Historic range: Common in New South Wales
Now: They have moved as far south as Tasmania and South Australia. These delicious crustaceans dislike warm temperatures and have sought refuge in the territory of red southern rock lobsters (Jasus edwardsii).
4. Gloomy octopus (Octopus tetricus)
Previous range: Common in New South Wales
Now: They can be found as far south as Tasmania during winter. Keep an eye out for these clever invertebrates in Tasmanian waters. It appears that their migration is permanent, as they have been nesting with their eggs in these new areas.
5. Whitetip reef shark (Triaenodon obesus)
Previous range: Northern Australia
Now: They have been spotted south of K’gari (formerly known as Fraser Island). Despite being classified as vulnerable in some regions, these slow-swimming, non-aggressive sharks pose little danger to humans.
6. Dugongs (Dugong dugon)
Previous range: Northern Australia
Now: Some have moved as far south as Shark Bay in Western Australia and the Tweed River in New South Wales. Australia’s waters are home to the largest population of dugongs in the world. However, as the waters warm, these shy sea-cows are migrating southward, resulting in more frequent sightings and encounters as they graze on seagrass meadows. In fact, in 2014, a kitesurfer reported seeing a dugong at City Beach, Perth, which is significantly outside their typical range. Experts predict that as the warming trend continues, more dugong sightings are likely to occur beyond their traditional habitat.
7. Red emperor (Lutjanus sebae) and other warm water game fish
Previous range: Northern Australia
Now: These fish, including red, threadfin, and redthroat emperors, are now appearing much further south, particularly in Western Australia. The Leeuwin Current acts as a warm water highway for these species, making this region a hotspot for their migration. These game fish are highly sought after by fishing enthusiasts.
8. Long-spined sea urchin (Centrostephanus rodgersii)
Historic range: New South Wales and Victoria
Now: These spiky sea creatures can be found in southern and western parts of Tasmania. Their larvae have migrated across the Bass Strait to their new home due to warming waters. However, the proliferation of urchins poses a threat to kelp forests and the species dependent on them. As a measure to mitigate the impact, Tasmanian authorities are working on establishing a sustainable urchin fishery to control their numbers.
If you spot any species that are not usually found in your local waters, you can participate in the Redmap citizen science project by uploading your sighting and photo. These observations from the public are invaluable for scientists to better understand the effects of climate change on various ecosystems.
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