The San Joaquin River Restoration Program set a new record this year for returning adult spring-run Chinook salmon: 448 and counting – the highest number of captured returns recorded since the Program started reintroducing spring-run juveniles in 2014.
“The high return numbers clearly demonstrate that spring-run Chinook can survive and return to spawn in the San Joaquin River” said program manager, Dr. Donald Portz. “We look forward to a future where salmon will be able to swim unencumbered all the way to spawning grounds below Friant Dam.”
The previous record for captured natural returns was 93 set in 2021.
Due to multiple in-stream structures which halt their migration upstream, the San Joaquin’s returning spring-run Chinook must be captured in fyke traps – large diameter mesh cylinders placed in the river – before they are trucked in a tank approximately 120 miles to Reach 1 of the Restoration Area near Friant Dam and released.
“Our fish need the cooler water and habitat of Reach 1 in order to hold over the summer before they spawn in the fall,” said the Program’s lead fish biologist, Dr. Oliver “Towns” Burgess.
While most of this year’s adults were caught in fyke traps located in the Eastside Bypass downstream of the State of California’s Eastside Bypass Control Structure, spring-run Chinook were also trapped and hauled from Sack Dam, about 45 miles upstream of the control structure. Earlier in March and April, higher river flows allowed salmon to get past the Eastside Bypass Control Structure and at least one got up to Sack Dam – the next in-stream impediment after the control structure.
“We expect to begin construction on the Arroyo Canal Fish Screen and Sack Dam Fish Passage Project at the end of the summer this year,” said Program Manager Portz. The project will allow fish to pass around Sack Dam and avoid diversion into Arroyo Canal.
“Installing a fish screen for Arroyo Canal will benefit both fish and farmers by protecting salmon from straying into canals while allowing water users to continue their lawful water use,” said Portz. Portz said he also expects passage at the control structure to be completed by the same time passage at Sack Dam is completed in summer 2028. Currently, unless high river flows are present, fish are unable to make their way past the control structure.
While it was high flows that allowed salmon up to Sack Dam this year, Burgess also pointed out that flood conditions in the winter of 2023 increased flows for juvenile Chinook headed out to the ocean and improved their outmigration.
Spring-run Chinook salmon are anadromous, meaning, they begin their lifecycle in fresh water before migrating out to the ocean. There, juvenile salmon mature for several years in salt water before returning as adults to their natal rivers and streams to complete their lifecycle by spawning before they die.
In 2019, the Program saw a record number of redds, or fish nests, created in the river. 2017 was also a wet year on the system (like 2023) and field crews were unable to continue monitoring operations due to the high river flows. However, because over 200 redds were counted in the river during the 2019 spawn, biologists estimated salmon had been able to swim past in-stream obstacles and over 400 adult spring-run adults gained access to spawning grounds. And like the 2023 high-water year, newly hatched juveniles in 2017 were aided by the larger river flows when outmigrating to the ocean, thus more survived and contributed to the large number of returning adults in 2019.
“Given the record-high number of returns this year, we’re hopeful that we surpass the 2019 record for redds this summer,” added Burgess.
The spring-run migration is expected to wind down by early June. As is their lifecycle, the salmon will hold in Reach 1 until September when spawning will commence, with the emerging generation expected in November before outmigrating to the ocean in spring.
Watch a video of our trap and haul operations for spring-run Chinook returns below!