Scales Can Distinguish Between Wild and Farmed Salmon

SOUTHAMPTON, England, Oct. 5 (UPI) — British scientists have developed a new technology that can distinguish between farmed and wild salmon by examining the chemistry of their scales.

University of Southampton geochemist Clive Trueman, who led the research in collaboration with the Scottish Association for Marine Science, said fish scales are formed from the same chemicals as bones and teeth, preserving a chemical record of the water the fish lived in throughout its whole life. The scientist found levels of the trace metal manganese were always much higher in fish of farmed origin.

“This is probably caused by manganese supplements in fish food, and also because conditions underneath the fish cages promote recycling of manganese in the water column,” Elizabeth Adey, lead author of the research, said.

Using relatively simple techniques, the team said it was able to distinguish between farmed and wild fish with 98 percent accuracy.

“Because of its non-destructive nature, this technique could be used to assess the proportion of farm escape salmon present in any river, and therefore identify where additional conservation and wildlife protection measures are needed,” Trueman said.

The team also found differences in the chemistry of scales between fish farms that might allow researchers to identify individual farms responsible for the release of wild fish.

The research appeared in the journal Marine Ecology Progress.

Copyright 2009 by United Press International

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