Smolt Monitoring Project Week 5: Fish Identification

Author: Devan Reid, Sr. Fisheries Technician

This week at the Salmon River trap, Fisheries Technicians Ben and Jason PIT-tagged 600 hatchery and 12 wild Chinook salmon smolts.  A few hatchery and wild steelhead trout smolts were also captured and are expected to arrive in greater numbers as river flows increase in the coming weeks.  Also captured this week were a few more Dworshak Reservoir kokanee salmon at the Snake River trap that we speculate were flushed through Dworshak Dam during recent water releases. The crews are excited for the busier days to come when more fish should be arriving.

These traps target migrating juvenile Chinook salmon and steelhead trout, known as smolts that are bound for the ocean. The smolts generally range from three to four inches in length for Chinook smolts and six to eight inches for steelhead smolts. The traps do not try to catch adult fishes. However, a couple of post-spawn adult steelhead trout swim in each spring that are counted and released.

The trap crews expect to catch a variety of fish species from now through May. Chinook salmon and steelhead trout are the two species targeted for PIT-tagging and monitoring by the crews. Hatchery and wild fish can be differentiated in a few ways but the most obvious difference is that wild fish do not have their adipose fins clipped. Some hatchery fish do not get adipose-clipped and you can read on the reasons why in the past blog, “Not all hatchery steelhead are adipose-clipped.”  Other species captured in the trap include kokanee salmon, Pacific lamprey, coho salmon, and sockeye salmon. These species are counted and reported to Fish Passage Center along with the Chinook salmon and steelhead trout.

Idaho Department of Fish and Game and the Fish Passage Center cooperatively operate this fish trap as a key component of the Smolt Monitoring Program and the Comparative Survival Study. More information about these important wild salmon and steelhead trout projects is available at

For more information on Idaho’s wild salmon and steelhead click here

  • 6-20-01sh2
    Creative Commons Licence
    Scott Putnam