With the recent development of a technique that tests the chemicals of their scales, farmed salmon can now be distinguished from wild, according to researchers from the National Oceanography Center in Southampton.
Fish scales are formed from the same chemicals as bones and teeth and grow like tree rings, preserving a chemical record of the water the fish lived in throughout its whole life, the researchers said. Scales are easy to collect, and can be removed from fish without harm, which is important when studying an endangered population. The researchers discovered that levels of the trace metal manganese were always much higher in farmed fish.
The team also found differences in the chemistry of scales between fish farms, which might allow researchers to identify individual farms responsible for the release of wild fish — although this would require additional work.
The technique is 98 percent accurate.
"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," said Dr. Clive Trueman, a geochemist with the University of Southampton's School of Ocean and Earth Science, based at that National Oceanography Centre.
Trueman also said the ability to determine between the two can help prevent fraudulent labeling.
October 1, 2009
