Trucking juvenile salmon from Central Valley hatcheries to areas downstream of the Delta is known to increase overall fish survival. This is a vital program in maintaining a viable commercial and recreational fishery, and escapement back to the Central Valley. However, that action can also increases straying of adult fish to non-natal areas which is considered undesirable.
At various SF Bay release sites and in Monterey Bay trucked fish are placed into net pens for a few hours to allow them to recover from stress and adapt to the salinity and temperature conditions at the nets. If the fish arrive in good shape from the hatchery, most survive at the net locations.
Recently hatchery managers have used release sites for a maximum of two days before switching to alternative release locations due to predators homing to the site after two days. After a five day rest, a site can be used again. This has greatly increased survival of fish formerly released on day three and beyond. Other release improvements include releasing from the net pens on the outgoing tide in mid channel and releasing late in the day when predatory birds have stopped feeding for the day.
Half Moon Bay Net pen
In 2012, the Coastside Fishing Club tested acclimation of 180,000 smolts at Half Moon Bay. The pen acclimation time is three to five days. Survival improved and a high percent of the mature adults returned to the area two years later. Each year the program was expanded and in 2018, they acclimated 750,000 smolts in net pens at the site. The GSSA plan calls for the eventual release of 2 million smolts annually.
Development of this saltwater acclimation technology has demonstrated that the ocean survival of these fish is 300 to 400 percent better than other release systems. Because a high percentage of the mature adults are harvested, the numbers of hatchery returns and strays are reduced.
Agencies Involved – CDFW, NMFS
Species Benefit – Fall-Run
Ballpark Cost- $200,000 at 25 percent coded wire tagged
Years to Complete – One to Two
Increase in Ocean Abundance – 48,400 adults annually at 2 million smolts acclimated.
Ft. Baker Ocean Releases
For the past few years, CDFW has been successfully releasing multiple loads of 100,000 smolts from the Feather and Mokelumne hatcheries to Fort Baker. In 2019, 1,900,000 smolts were released at the site and the plan contemplates future transfers of trucked fish from Mare Island to Fort Baker.
This site, which is near the Golden Gate appears to have the same highly favorable survival figures as the Half Moon Bay site. Releases are direct without net pens. Most of the releases are made in the late afternoon or at dusk on an outgoing tide. This avoids most of the bird and water predator losses.
Agencies Involved – CDFW
Species benefits – Fall-Run
Ballpark Cost – $200,000 at 25% CWT Years to Complete – One to Two
Increase in Ocean abundance over San Pablo releases at 2 million smolts is 48,400 adults annually