CWT STUDY

The MBSTP Chinook Program engages anglers in data collection. The coded wire tags (CWT) placed in the Chinook are recovered by anglers and provided to CDFW for data entry and analysis. The Chinook smolts are provided by either Feather River, or Mokelumne hatchery. Each of the 240,000 fish are marked (fin clip), vaccinated, and CWT emplaced at MBSTP expense and by MBSTP volunteers. The fish are then brought to Santa Cruz Harbor by tanker truck in groups of 60,000 fish, acclimated to salt water in the net-pen and released after one week. After the four groups are acclimated and released, the net-pen is disassembled and stored. Anglers are encouraged to fish and recover the CWT’s (salmon head). CDFW agents collect the data at the harbor landing.  The 5-year CWT study has yielded plenty of data but has not yet been summarized. The study period is likely to be extended beyond the original time frame.

An environmental concern addressed in this study is that the Sacramento Chinook (including hatchery produced fish) are not making a successful out-migration. If the recovery of CWT’s from net-pen acclimated fish is a high percentage of the total Chinook caught then this is clear evidence of the failure of the natural (and hatchery supplemented) fish that out-migrated the Sacramento to reach maturity. The results of the study can be used to justify greater efforts to make Chinook out-migration from the Sacramento safer for the fish.

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