Quote form the Hood River Broodstock Study
" The similar fitnesses Hnew x Wild and Wild x Wild pairs, suggest that having Hnew fish in the system is probably not obviously dragging down the fitness of the wild population for gentic reasons."
The key words in that assertion are "probably" and "not obviously".... not terribly reassuring.
"Probably" implies there is still an element of uncertainty.
"Not obviously" implies that the reproductive fitness could be dragged down in more subtle, less obvious ways than one might appreciate at first glance.
Here's what disturbs me. If wild fitness (W) is 1.0 and the average hatchery fitness (H) is only 0.85, then each (W x H) pairing on the spawning gravel will only bring back 85% of the fish that would return from a (W x W) pairing. If two hatchery fish spawn with one another (H x H) then the productivity goes down to 72% of a (W x W) pairing.
In other words, even with the new and improved breed of hatchery fish, their introgression into the wild population would still diminish reproductive rates of each spawning event by 15-28%, depending on the pairing.
Is that an improvement over the miserable 10% fitness of out-of-basin stock? ABSOLUTELY. If you carry the same analysis through for the old hatchery stock, their introgression would reduce productivity by 90-99% depending on the pairing.
In either case, hatchery fish allowed to spawn in the wild compete with their wild counterparts for spawning habitat. Their progeny compete with wild juveniles for limited rearing habitat. In the end, these hatchery fish deprive their wild counterparts of space and forage, consuming limited resources, and bringing fewer surviving adults back to the system to keep the population going. And it's for that reason that fish managers should make EVERY attempt to keep these fish off the gravel.
Now don't get me wrong. If the goal of the program is to produce high quality fish for the masses to harvest, great, this is an excellent way to do it. BUT if the mechanism does not exist to prevent those hatchery fish from spawning naturally, then they ought not be planted in the system in the first place. It sounds to me like this is the Achilles heel of the Wilson program as I understand its operation from this thread. Encouraging the hatchery fish to spawn naturally throughout the basin is a losing proposition for the wild native population. Over time, they will suffer the consequences.
Think of it like your stock portfolio. As good as these wild broodstock hatchery fish are, they are under-performers. How long do you hold on to under-performing stocks in your portfolio? Would you continue to invest even more money in those stocks that continued to lose you money to the tune of 15-28% year after year after year?
Yeah, I thought so.