The concept that you can harvest hatchery escapements down to their minimum number is misguided. If the hatchery has a weir to stop the returning adults then the hatchery escapement will mirror the natural one. Take GH and it has always been managed for wild ( the Hump being the exception and no weir ) and that results in large hatchery returns. Point is the fish are not wasted they are the in river fishers opportunity. The word surplus is usually used to describe the number above the minimum 5% hatchery return needed by mixed stock fishers in estuary or similar fisheries in the salt and commercial fishers. Surplus is a hatchery term around eggtake requirements that gets hijacked by those trying to propel a harvest expansion not a biological rational.