[en] Downstream migrating salmon and steelhead (Oncoryhnchus spp.) smolts were monitored at the Rock Island Dam bypass trap from April 1--August 31, 1996. This was the twelfth consecutive year that the bypass trap was monitored. Data collected included: (1) number of fish collected by species, (2) number of fin clipped and/or Passive Integrated Transponder (PIT) tagged fish caught by species, (3) total number of fish showing signs of gas bubble trauma (GBT), (4) percent of descaled fish, and (5) daily average river flow, powerhouse number-sign 1 flow, powerhouse number-sign 2 flow and daily average spill. These data were transmitted to the Fish Passage Center (FPC), which manages the Smolt Monitoring Program throughout the Columbia River Basin. The Smolt Monitoring Program is used to manage the water budget, releasing upstream reservoir water storage allocated to supplement river flows during the downstream migration of juvenile salmonids