It was nearly noon. The time had come.
They’d been swimming around in a giant stainless steel tank on the back of a truck for nearly two hours.
Now, they’d be piped into a holding net — all 300,000 of them — where they could rest before their odyssey began.
Then, as mere infants, they’d be on their own, in the unforgiving waters of the California Delta.
The Chinook fingerlings’ release Tuesday near the Antioch Bridge was a turning point. The end of life in their aquatic nursery, the Mokelumne River Hatchery.
It signified the start of a new adventure in a wet, dangerous world.
Within hours or days, some will be lost. Others will be a light snack for a striped bass. And some of the smartest and strongest will venture into the San Francisco Bay and beyond, and live full lives before returning to the Mokelumne River. For the fishery manager who oversaw their fertilization, spawning and early development, Tuesday was filled with uncertainty.
“I only have control over what happens to them up to this point,” said William Smith, fish hatchery manager for the California Department of Fish and Game. “What happens out there is out of our hands.”
The little fishes’ life began in plastic buckets in November as Department of Fish and Game workers fertilized thousands of eggs and set them in specially designed troughs. The eggs that took to the procedure hatched in the following weeks and began gorging themselves on a high-protein feed.
They’ve grown several inches in recent months since being transferred to the rectangular raceways outside the hatchery. But the salmon can’t stay in the concrete ponds forever. They can’t be housed under the black protective netting that blocks the hawks circling overhead from indulging on an easy meal. The Chinooks must fend for themselves as they venture to and from the Pacific Ocean, morphing from hunted to hunters along the way.
Tuesday was a crucial day for the salmon. The salmon are in the smolt stage, meaning their natural instinct is telling them to head for the ocean. To give them the final push towards adulthood, workers gathered the Chinooks into tanker trucks and drove them to a spot near the Antioch Bridge to be released into the wild.
Even though the fish would be piped through a series of mechanisms and sloshed around during the long drive, Smith said he expects most of the fish to handle the first leg of the journey with ease.
“I expect we’ll only lose about 10 fish between the hatchery and Antioch,” Smith said.
The two 28,000-gallon tanker trucks and 1,200-gallon water truck were filled with lightly salted water before the fish were put inside. The salt reduces the stress on the fish and prepares them for conditions they will face in the Delta, Smith said. An anti-foaming agent was also added to the water before the fish were put in. The agent prevents scum from forming on the water and making the fish ill. Oxygen is also pumped into the tanker trucks to keep the water circulating during the drive.
To move the fish from the raceways to the truck, workers use a pump attached to a modified tomato harvester. The device stands about 12 feet tall and acts as a brief settling area before the fish are piped into the truck.
The gas-powered pump rumbles and shakes as the Chinooks are transported through the pipe into the harvester, which deposits them into a waiting truck. Hatchery workers take steps to reduce the thermal shock and other stresses the salmon will endure.
Since the harvester is designed to handle the soft flesh of fruit without damaging it, it’s an ideal option for transferring large numbers of fish safely, Smith said. Workers could simply siphon the fish from the raceways to the truck, but the harvester minimizes stress for the fish and reduces the risk of injury.
Once inside the trucks, the convoy heads for Sherman Island Levee Road. A brief stop is made on Peltier Road underneath Interstate 5 to perform a welfare check on the fish. After workers visually observe the contents of the tank to ensure the fish are still flopping away, the hour-long drive past wind farms and fields resumes.
Upon reaching the destination, workers take a minute to stretch their legs as they walk along the rocky levee. Winds whip the wild grasses as cars glide past the parked trucks on the narrow road. Alongside the truck is the shimmering waterway the fish will soon call home.
Workers attach the trucks to a 30-foot pipeline that deposits the fish into an acclimation pen. The pen is a pontoon boat with nets in its middle to temporarily trap the fish. Once the valve is opened, the fish flood out of the pipeline into the pen.
The pen — and the 300,000 salmon inside — is then taken to the middle of the waterway and left there for two hours. The nets are lowered and the fish are free to start their journey at that point. The acclimation pen is a vital step because it gives the fish time to adapt to their new environment, Smith said.
“It helps them get through the initial shock,” he said.
The hatchery will make three sets of releases between now and the end of May. Each release takes place over a period of days, and is responsible for distributing nearly 2 million salmon into the Delta. This release began last week and will continue through Thursday.
Although it takes 60 salmon put together to equal one pound, Smith said they are ready to go because their biological clock is ticking.
Later in the afternoon, the nets would be lowered and instinct would take over. Some fish will get sucked into pumps, while others will be eaten in the river or at sea. Others will take the bait of an angler and end up either mounted on a wall or drizzled in melted butter and slapped on a grill.
However, the strongest and smartest will survive. They will make the journey to underneath the Golden Gate Bridge and beyond. They will navigate to some of the coldest waters in the Pacific Ocean and feast on smaller fish for two to six years.
It will be at that stage in adulthood when the instinct that told them to head for the ocean declares that it’s time to head back upstream. The Chinooks will heed the call and swim back towards the Mokelumne River. If they survive the grueling trip, the anglers and stay on course, they will find their way back to the hatchery, where their eggs or milt can be harvested and a new cycle will begin.
Contact reporter Jordan Guinn at firstname.lastname@example.org.