An industry-scale mass marking technique for tracing farmed fish escapees.
Farmed fish escape and enter the environment with subsequent effects on wild populations. Reducing escapes requires the ability to trace individuals back to the point of escape, so that escape causes can be identified and technical standards improved. Here, we tested if stable isotope otolith fingerprint marks delivered during routine vaccination could be an accurate, feasible and cost effective marking method, suitable for industrial-scale application. We tested seven stable isotopes, (134)Ba, (135)Ba, (136)Ba, (137)Ba, (86)Sr, (87)Sr and (26)Mg, on farmed Atlantic salmon reared in freshwater, in experimental conditions designed to reflect commercial practice. Marking was 100% successful with individual Ba isotopes at concentrations as low as 0.001 µg. g-1 fish and for Sr isotopes at 1 µg. g-1 fish. Our results suggest that 63 unique fingerprint marks can be made at low cost using Ba (0.0002 - 0.02 $US per mark) and Sr (0.46 - 0.82 $US per mark) isotopes. Stable isotope fingerprinting during vaccination is feasible for commercial application if applied at a company level within the world's largest salmon producing nations. Introducing a mass marking scheme would enable tracing of escapees back to point of origin, which could drive greater compliance, better farm design and improved management practices to reduce escapes.
School of BioSciences, University of Melbourne, Parkville, Victoria, Australia.
Fletcher
F
Warren-Myers
School of BioSciences, University of Melbourne, Parkville, Victoria, Australia.
Tim
T
Dempster
Institute of Marine Research, Matre Aquaculture Research Station, Matredal, Norway.
Per Gunnar
PG
Fjelldal
Institute of Marine Research, Matre Aquaculture Research Station, Matredal, Norway.
Tom
T
Hansen
School of BioSciences, University of Melbourne, Parkville, Victoria, Australia.
Stephen E
SE
Swearer
D000818:Animals; D005398:Fisheries; D005399:Fishes / Q000254:growth & development; D007221:Industry; D007554:Isotopes; D010037:Otolithic Membrane
D007554:Isotopes