High prevalence of vaterite in sagittal otoliths causes hearing impairment in farmed fish.
The rapid growth of aquaculture raises questions about the welfare status of mass-produced species. Sagittal otoliths are primary hearing structures in the inner ear of all teleost (bony) fishes and are normally composed of aragonite, though abnormal vaterite replacement is sometimes seen in the wild. We provide the first widespread evaluation of the prevalence of vaterite in otoliths, showing that farmed fish have levels of vaterite replacement over 10 times higher than wild fish, regardless of species. We confirm this observation with extensive sampling of wild and farmed Atlantic salmon in Norway, the world's largest producer, and verify that vateritic otoliths are common in farmed salmon worldwide. Using a mechanistic model of otolith oscillation in response to sound, we demonstrate that average levels of vaterite replacement result in a 28-50% loss of otolith functionality across most of a salmonid's known hearing range and throughout its life cycle. The underlying cause(s) of vaterite formation remain unknown, but the prevalence of hearing impairment in farmed fish has important implications for animal welfare, the survival of escapees and their effects on wild populations, and the efficacy of restocking programs based on captive-bred fish.
Sustainable Aquaculture Laboratory - Temperate and Tropical (SALTT), School of BioSciences, University of Melbourne, Victoria 3010, Australia.|Research on the Ecology and Evolution of Fishes (REEF) laboratory, School of BioSciences, University of Melbourne, Victoria 3010, Australia.
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Reimer
Sustainable Aquaculture Laboratory - Temperate and Tropical (SALTT), School of BioSciences, University of Melbourne, Victoria 3010, Australia.
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Dempster
Sustainable Aquaculture Laboratory - Temperate and Tropical (SALTT), School of BioSciences, University of Melbourne, Victoria 3010, Australia.|Research on the Ecology and Evolution of Fishes (REEF) laboratory, School of BioSciences, University of Melbourne, Victoria 3010, Australia.
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Warren-Myers
Norwegian Institute for Nature Research (NINA), PO Box 5685 Sluppen, 7485 Trondheim, Norway.
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Jensen
Research on the Ecology and Evolution of Fishes (REEF) laboratory, School of BioSciences, University of Melbourne, Victoria 3010, Australia.
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Swearer
D000827:Animal Welfare; D000818:Animals; D017756:Aquaculture; D002119:Calcium Carbonate / Q000032:analysis*; D005393:Fish Diseases / Q000453:epidemiology* / Q000503:physiopathology*; D034381:Hearing Loss / Q000453:epidemiology / Q000503:physiopathology / Q000662:veterinary*; D009664:Norway; D010037:Otolithic Membrane / Q000737:chemistry*; D020317:Salmo salar
D002119:Calcium Carbonate