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Time, effort, and knowledge needed to accomplish harvest augmentation is much less than that needed for natural production supplementation. In order to supplement natural production, managers need to know several factors. They need to know the ecology of the area, the factors limiting present production, the unique qualities of the stock of fish to be supplemented, and the most efficient means for supplementation. The time frames for determining success stretches into multiple life cycles for natural production supplementation while for harvest augmentation we can determine success in one generation. Fishery agencies have been stocking anadromous fish for many years in the Pacific Northwest. There have- been reports of increasing adult returns from various -types of planting strategies. Outplantings of smolts return the highest percentage of adults far both salmon and steelhead. However, there are mixed results on the ability to rebuild or increase natural runs by supplementing with hatchery fish. A few examples suggest that it is possible to supplement natural runs with hatchery fish without adverse effects. For instance - in Oregon, the Elk River run of fall Chinook has been supplemented far approximately 20 years. Although no major adverse effects have been noted from this highly controlled supplementation program, the natural run of fall Chinook did not significantly increase either. Managers believed the Elk River wild run was at carrying capacity prior to supplementation. In Idaho, plants of steelhead fry in some upper Salmon River drainages is believed to have, contributed to the building up of natural spawning fish in a few of the drainages. Streams with no apparent spawning were planted with excess fry and in subsequent years spawning adults were noted. No numerical information is available for these obsereiations, and straying can not be ruled out. In BC, Coquihalla River biologists, supplementing with hatchery fry, have documented steelhead fry-to-adult survival as high as 1.3 percent and parr-to-adult survival of 2.6 percent for hatchery fish. After releasing hatchery fry, a fourfold increase in standing crop of the stream was noted. Long range .build-up of natural production was not shown because of the continuous annual stocking programs. In New England, work with Atlantic salmon demonstrates how difficult it is to rebuild and reestablish anadromous fish runs. Stockings of fry and smolts have both returned adults but natural production has not really taken off. `Following are conclusions we arrived at based on our review of supplementation: ~` -Chinook salmon, particularly upriver stocks, are the most difficult to supplement r successfully with hatchery fish. This is because of the greater distance from the ocean and the longer freshwater life cycle. -The stock of fish is an important factor to consider when supplementing. The closer the hatchery stock is to the supplemented stock or original natural stock, the better chances are for success. Ideally, the hatchery supplementation brood fish should be taken from the natural stock that is to be supplemented. 37