Rob-
Let's talk a minute about steelhead return rates.
Wild steelhead are subject to high mortalities at evey step of their lives. If a typical wild female where to lay 5,000 eggs in her redd it is common for only 35 or so to survive the incubation in the gravel, learn to find food, find good living space, escape a wide range of predators, find save havens from floods and a host of other perils to become smolts. The result is that the 35 or so smolts that survived their typical 2 years in freshwater are not only the luckest but the most fit (those the grow the best, are able to escape all predators). As a result they are survivors - the best equiped to survive in their new marine home. Average survival of those wild smolts are typically in the 10% (though recently it has been lower). Thus that spawning pair of fish that produced 35 smolts would produce 3 or 4 returning adults on the average.
Contrast this with the case of a pair of hatchery fish. The female often has less eggs than her wild counterpart - typically around 3,500. Of those 3,500 eggs we can expect at least 2,500 to 3,000 to survive to become smolts in a year. The reason of course is that in a hatchery they are protected from floods, diseases, most predators, are fed regularly, etc. The result is a high survival to the smolt stage however the fish are not as fit - the slower swimmers, the less aggressive fish etc have not been removed from the population. Meaning that they are not as well adapted as their wild counterparts to avoid the perils of their migration down the river and thorughout the Pacific ocean. Thus the lower smolt to adult survival.
However using a low of 1% smolt to adult survival on 2,500 smolts means that the pair of hatchery fish are likely to produce 25 or more returning adults.
In terms of producing returning fish to the river to support fishing and yes even harvest hatchery fish are several times more productive wild fish. Please note that I'm not saying that hatchery fish are in any way superior to wild fish except for producing numbers of fish to support fisheries.
Tight lines
Smalma