Use of sulphur and carbon stable-isotope composition of fish scales and muscles to identify the origin of fish

δ³⁴S and δ¹³C analyses were used to determine the origin of trout specimens. The isotope record of their scales and muscles are compared with a database previously obtained from wild- and reared fish coming from Polish rivers and pond farms. The comparison made it possible to find out whether the trout were wild or reared.