One way the Bay Program may provide technical assistance to the Pamunkey Indians is to help them "mark" their hatchery fish before releasing them - something that will help them identify returning shad and determine the effectiveness of their hatchery.
Shad fry reared at all other hatcheries around the Chesapeake are marked with tetracycline antibiotics before being released. Shad fry, as young as 3 days old, are immersed in a tetracycline solution that is absorbed into growing bone tissue. At that early age, the otolith, or earstone, is the only true bone present in the fish. The otoliths grow by adding rings, similar to the rings in tree trunks, except that one ring is developed each day. A fry immersed at three days, for example, produces a tetracycline mark in the third ring. Additional immersions at later dates produce multiple marks.
Each hatchery around the Bay treats shad with tetracycline at different intervals to achieve a unique mark that can be distinguished when the otolith is examined under a microscope. This allows biologists to measure the effectiveness of their hatchery operation by estimating the number of hatchery fish that return to spawn in their river of origin when they reach maturity, usually after three to six years.