Smolt Monitoring

Downstream Migrant Smolt Trapping

California Sea Grant biologists operate funnel net traps on Mill, Green Valley and Willow creeks each spring to monitor the downstream migration of coho smolts, one-year old fish, as they make their way to the ocean. Sonoma Water also operates a smolt trap on Dutch Bill Creek (among other streams). Data collected during smolt trapping efforts support estimates of smolt abundance, overwinter survival and growth. Abundance estimates generally range in the thousands, though numbers vary greatly across years and streams depending on how many Broodstock Program fish are stocked the previous seasons. 

See the Spring Monitoring reports on our Reports & Publications page for a detailed overview of downstream migrant smolt trapping methods and outcomes for each year. 

Scanning a coho smolt for a PIT tag. Photo: Joshua Asel
Scanning a coho smolt for a PIT tag. Photo: Joshua Asel
A coho salmon smolt is weighed at the Mill Creek smolt trap site
A coho salmon smolt is weighed at the Mill Creek smolt trap site
A coho salmon smolt is weighed at the Mill Creek smolt trap site
Sea Grant biologists netting fish from downstream migrant smolt trap box on Mill Creek