USE OF DISSOLVED STRONTIUM IN SCALE MARKING OF JUVENILE SALMONIDS - EFFECTS OF CONCENTRATION AND EXPOSURE TIME

Strontium (Sr), which is chemically similar to calcium and can substit ute for this element in bony tissues of fishes, shows promise as an in expensive and efficient means of chemically marking juvenile salmonids . This study examines the effects of three different Sr concentrations in water (1.8, 3.6, and 5.4 mg/L) and two different exposure times (3 0 and 60 d) on uptake of Sr into the scales of juvenile rainbow trout (Oncorhynchus mykiss). Doubling and tripling the Sr concentration in t he ambient water produced corresponding twofold and threefold increase s in final scale (Sr). A twofold increase in exposure time produced ne arly the same effect as a twofold increase in concentration. Widesprea d adoption of this technique will require establishment of optimal con centration and exposure times, validation of methods for compensating for Sr incorporated during seawater residence, and development of hatc hery-specific chemical markers using combinations of several different elements.