Environment

Drought prompts truck and release of salmon smolts in Rio Vista

Chinook salmon smolts trucked in from Coleman National Fish Hatchery flip and jump wildly while being released into a net pen in Rio Vista in the second year of a special drought contingency plan.
Chinook salmon smolts trucked in from Coleman National Fish Hatchery flip and jump wildly while being released into a net pen in Rio Vista in the second year of a special drought contingency plan. rpench@sacbee.com

In a bid to save some of the 12 million juvenile Chinook salmon from near-certain death, federal wildlife officials in California are trucking fish to the Delta for release.

The move – necessitated by the state’s continuing drought – began last week as container trucks began arriving in Rio Vista. With six trucks on the job, the process is expected to take 22 working days. It’s the second straight year the fish have been trucked for release.

The salmon smolts, about 3 inches in length, are typically released into Battle Creek, a tributary of the Sacramento River, near the Coleman National Fish Hatchery in Anderson. Releasing the fish upriver increases the odds the salmon will return as adults, but given the low water levels and warm water temperature on the Sacramento River, biologists feared too few would make it to the ocean, thus have no chance of returning to mate.

“Trucking our juvenile salmon to the Bay-Delta is not normal procedure for Coleman National Fish Hatchery, but due to the drought, it is the best option we have this year,” said Robert Clarke of the U.S. Fish & Wildlife Service. “Trucking juveniles drastically increases straying and reduces adult returns to the upper river and hatchery. However, if we were to release our fish at the hatchery under the current drought conditions, it is very likely we would not get enough adults back to meet our egg needs three years from now.”

The process of transporting the juvenile salmon is expected to run through mid-May, as the fish are taken to one of three sites some 180 miles from the Coleman hatchery. Once transported to the Rio Vista, Mare Island or San Pablo Bay site, the Chinook smolts are placed in pens for about an hour to acclimate to the environment before they are released.

One-by-one, trucks holding 2,800 gallons of water and up to 130,000 smolts are backed up to a pipe that takes the fish across the dock and into a waiting net. Thursday, as the first truck released its cargo, the water surface sprung to life as thousands of active young fish tested their fins, leaping to the surface. Within minutes, the activity calmed as the fish settled into their new surroundings. Once the four trucks had unloaded, support staff waited for the right tide conditions before pulling the barge with three nets into the middle of the Sacramento River and releasing the smolts.

The process cuts short the normal swim. The young salmon normally take several days to three weeks to make the voyage, said Clarke.

Last year, fish and wildlife officials transported and released 7.5 million smolts before a late March storm improved conditions to the point where 4.5 million more could be released upriver. If conditions don’t improve, all 12 million will be released in the Delta this year.

The federal hatchery program was created to offset the impact of creating the Shasta and Keswick dams on the upper Sacramento River.

Call The Bee’s Ed Fletcher, (916) 321-1269. Follow him on Twitter @NewsFletch.

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