Strontium marking of hatchery-reared coho salmon (Oncorhynchm kisutch, Walbaum)

In the management of saimonid populations it is often necessary to distinguish hatchery-reared from wild stocks. This study examines the feasability of marking fish tissue by substituting a biologically rare element, strontium, for calcium.
Sixteen-month-old hatchery-reared coho salmon ( Oncorhynchus kisutch , Walbaum 1792) were fed a diet, to which 10000 ppm stable strontium was added, for 60 days. Prior to their seaward migration in June 1976, the treated coho contained 32 times as much strontium in their vertebrae as did the control coho.
Sixty-eight precocious males'jacks' returned to the hatchery in the fall of 1976 and 1200 adults in the fall of 1977. Strontium-treated 'jacks' contained 1·4 times as much strontium as did control 'jacks' however, treated and untreated fish could not be distinguished as adults. The reduction in the strontium concentration of the treated fish could be accounted for by growth.