Tropical Fish Invade Australia’s Coasts: DNA ‘Fingerprints’ Expose Climate-Driven Migrations
Tropical fish are migrating to Australia’s temperate coasts due to climate change, revealed by DNA analysis.
A groundbreaking study published in Diversity and Distributions unveiled how climate change is driving tropical fish species to migrate into temperate waters along Australia’s east coast, one of the fastest-warming marine regions globally. Conducted by researchers Chloe Hayes, Angus Mitchell, and Ivan Nagelkerken, the study leverages environmental DNA (eDNA) to detect these hidden shifts, offering a clearer picture of how marine ecosystems are responding to rising ocean temperatures.
Climate change has already prompted over 12,000 species worldwide to relocate across land, freshwater, and marine environments to escape unfavorable conditions or access new habitats. In Australia, tropical fish are increasingly appearing in temperate reefs, particularly in Sydney’s waters, as they seek cooler environments. Traditional visual surveys, conducted by researchers or citizen scientists, often miss small, rare, nocturnal, or cryptic species that hide in caves. This limitation has led to an underestimation of the true scale of species migration.
To address this, the research team adopted a forensic approach, analyzing eDNA—genetic material shed by fish through mucus, scales, and waste—collected from seawater samples along a 2,000-kilometer stretch of Australia’s east coast. This included tropical reefs of the Great Barrier Reef, subtropical waters, and temperate kelp forests in New South Wales. By filtering and sequencing seawater samples, the team identified species invisible to traditional methods, complementing visual surveys conducted along transect belts.
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The eDNA analysis revealed tropical species, such as the lined surgeonfish (Acanthurus lineatus), striated surgeonfish (Ctenochaetus striatus), common parrotfish (Scarus psittacus), black-blotched porcupinefish (Diodon liturosus), silver sweeper (Pempheris schwenkii), and speckled squirrelfish (Sargocentron punctatissimum), in temperate ecosystems where they had not been previously recorded. These species, often small or nocturnal, evade detection by divers, highlighting eDNA’s ability to uncover hidden migrations.
Conversely, visual surveys proved more effective at detecting temperate species, demonstrating that eDNA complements rather than replaces traditional methods. The combination of both approaches provides a comprehensive understanding of shifting fish communities, critical for tracking climate-driven changes in marine biodiversity.
The study’s findings are not unique to Australia. Globally, species are relocating due to altered temperatures, ocean currents, and habitats caused by climate change. While some species may adapt to new environments, others face challenges, potentially disrupting ecosystems. The researchers emphasize that advanced monitoring techniques like eDNA are essential for understanding these transformations and informing conservation strategies.
As Australia’s marine ecosystems continue to evolve, this innovative use of eDNA underscores the urgency of tracking species on the move. By revealing the unseen impacts of climate change, the study provides critical insights for protecting marine biodiversity and ensuring the resilience of ocean ecosystems in a rapidly warming world.
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