Perfectly normal or not, wouldn't it be an advantage to know what the loss was from before you address long term viability for hatchery supplementation? Oncy T's last link spoke directly to what types of selective traits can skew genetic success/productivity results. We don't even know what the cause is, much less how it affects attributes we select for supplementation. What kind of accuracy will we get from studies done with an 800lb gorilla in the room? As excited as I was to learn the possible opportunities associated with such a controlled study, it all falls apart with the amount of unknown impact.