Bill Sears, Science & Policy Analyst
Natural Resources and Lands Management Division
SFPUC Water Enterprise
November 8, 2022
Lower Tuolumne River fall-run Chinook salmon:
background and update
Operated by the San Francisco Public Utilities Commission
Fall-run Chinook salmon lifecycle
Happening now:
“escapement”
2-4 years ocean rearing
What is escapement?
Escapement is literally…adult fish that “escape” harvest and mortality to spawn in rivers (aka immigration) Tuolumne fall-run juveniles (springtime outmigration)
– Lower Tuolumne mortality
– San Joaquin River mortality
– Bay/Delta mortality (including state & federal pumps) – ocean mortality
– ocean harvest (commercial & recreational)
– freshwater harvest (recreational)
– pre-spawn mortality
= fall-run adult escapement
How do we know what’s happening with these fish?
• Adult escapement counting weir – counts adults on their way in • Rotary screw traps (RSTs) – estimate numbers of juveniles on their way out • The two RST locations allow estimation of juvenile survival between the two traps Waterford RST
(out-migrating juveniles)
Grayson RST
(out-migrating juveniles)
Adult escapement counting weir
(up-migrating adults)
Don Pedro Dam
La Grange Dam
Lower Tuolumne River Watershed
How is the escapement looking so far?
Season total, 9/30-10/27
87 adults
Tuolumne fall-run have been declining over the decades
New Don Pedro Dam completed
Ocean/fisheries collapse & closure
FSA implementation (higher base + pulse flows)
DroughtDrought Drought Drought
The spring flow/escapement relationship has broken down Contributing factors to low escapements
8 • Outmigration mortality – juveniles don’t survive their trip to the ocean • Tuolumne escapement mostly stray hatchery fish
• Juvenile hatchery fish did not rear in the Tuolumne, thus the disconnect between spring flow and escapement • Due to hatchery strays, we’ve lost the natural Tuolumne-adapted fall-run population • Hatchery-derived offspring likely have lower productivity • Commercial and recreational harvest doesn’t distinguish between natural and hatchery fish • Commercial harvest was between 53% to 68% of Central Valley fall-run adults from 2014-2018 • Drought, ocean conditions collapse
• Non-native, invasive plants (hyacinth) blocking adult migration in sequential dry years What are we doing about it?
9 • Voluntary agreement includes measures to increase in-river productivity and survival • Habitat restoration
• Floodplain rearing flows
• Larger spring pulse flows to increase juvenile survival • Predation suppression to increase juvenile survival
• However, hatchery strays will continue to undermine efforts to improve Tuolumne escapement Where are the fall-run Chinook hatcheries?
10 • 5 fall-run chinook production
hatcheries
• 4 operated by CDFW
• 1 operated by the USFWS
Map courtesy of FishBio
Upper Tuolumne River
Lower Tuolumne River
What’s next?
11 • Escapement updates:
December and January
• Juvenile outmigration
updates: Feb, Mar, & April
March and September: UTREP spring ecosystem
management releases from O’Shaughnessy Dam