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 substitute for this element in bony tissues of fishes, shows promise as an inexpensive 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 (30 and 60 d) on uptake of Sr into the scales of juvenile rainbow trout (Oncorhynchus mykiss). Doubling and tripling the Sr concentration in the ambient water produced corresponding twofold and threefold increases in final scale (Sr). A twofold increase in exposure time produced nearly the same effect as a twofold increase in concentration. Widespread adoption of this technique will require establishment of optimal concentration and exposure times, validation of methods for compensating for Sr incorporated during seawater residence, and development of hatchery-specific chemical markers using combinations of several different elements.