Marking Nonfeeding Salmonid Fry with Dissolved Strontium

Abstract

Chemical marking is a simple, inexpensive, and rapid technique for marking young salmon. We have marked nonfeeding embryos by adding strontium to their rearing water. Strontium, a harmless element in its natural form, resembles calcium chemically and is therefore readily incorporated into bone. Our data show that the best time for inducing a Sr mark into nonfeeding salmon fry is after hatching, when bone development begins. The addition of 1 μg Sr/mL to the rearing water of salmon fry for a period of 49 d resulted in a 10-fold increase in their vertebral Sr concentration. As the salmon grew, the induced mark became diluted in a predictable manner, but was still detectable after 169 d.