People should understand that hydridization of H and W occurs in virtually every hatchery-planted stream.

When it occurs on a small scale the harm is difficult to measure.

When it happens on a large scale, wild fish suffer. Volume is critical.

This is the problem with integrated hatchery programs where genetic material freely flows between wild and hatchery fish . Clearly, most of them are POORLY integrated.... meaning that the hatchery influence on the integrated population are excessive. Clearly, this is a case of less is best. But how much is too much?

Scientists have come up with the concept of PNI (proportionate natural influence) a ratio to quantify how much hatchery fish are affecting the genetics of the "integrated" population. A PNI of 1.0 describes a 100% wild population with zero hatchery influence. A PNI of 0.0 describes a population completely dominated by hatchery fish with essentially ZERO wild inputs.

Mathematically, PNI = P(nob) / [P(nob) + P(hos)],

where P(nob) is the proprtion of wild fish in the hatchery broodstock and P(hos) is the proprtion of hatchery fish on the gravel.

HSRG has set as a minimum standard that a well-integrated hatchery program have a PNI of at least 0.67. The key to meeting this objective is maximizing the proportion of wild fish in the brood and/or minimizing the proportion of hatchery strays on the gravel.

If a hatchery uses 100% wild broodstock, it should operate at a volume that allows no more than 50% of the spawners on the gravel to be of hatchery origin. (PNI = 100 / [100 + 50] = 0.67 ) However, the smaller the proportion of wild fish taken for broodstock, the lower the number of hatchery fish that should be permitted to reach the gravel.

Let's say only half the brood fish are wild-origin. The PNI standard of 0.67 would direct fish managers to allow no more than one out six of the spawners on the gravel to be hatchery fish.

The minimum standard for an integrated program is for at least 30% of the hatchery broodstock to come from the wild. Turns out this is often a very difficult standard to meet for many many hatcheries. At that P(nob), fish managers could allow at most 15% of the spawning escapement to be of hatchery origin if they are to remain true to HSRG recommendations.

We're CLEARLY a long ways from that.