We propose to quantitatively evaluate the relative reproductive success of naturally spawning hatchery and natural origin steelhead in the Columbia Basin. Hatcheries are one of the main tools that have been used to mitigate for salmon losses caused by the construction and operation of the Columbia River hydropower system.  In addition to harvest augmentation, hatcheries have recently been used in attempts to protect stocks from extinction (e.g., captive breeding) and attempts to enhance natural production (supplementation).  Surprisingly, little is known about how much the investment in hatcheries benefits or harms natural production.  We propose to take advantage of recent technological advances in genetics to empirically monitor the reproductive success of hatchery and natural steelhead using a DNA-based pedigree approach.  For this contract period, we will continue to trap and collect DNA and biological data from all steelhead released upstream of the weir, conduct intensive spawning ground surveys and collect DNA samples from progeny (i.e., parr and smolts) of previous brood years.  Specifically, we will (1) directly measure the relative reproductive success of hatchery and natural-origin steelhead  in a the natural environment, (2) determine the degree to which any differences in reproductive success between hatchery and natural steelhead can be explained by measurable biological characteristics such as run timing, morphology or behavior, and (3) estimate the relative fitness of hatchery-lineage steelhead after they have experienced an entire generation in the natural environment.