Net Pen Rearing of California Chinook Salmon

(NOTE: I’m getting hit up with lots of questions this year about the smolt acclimation project that’s happening in the Sacramento River basin this spring, so I thought I’d repost this to give you some inside info).

You have no doubt heard about how California and the Feds, in response to extreme drought conditions in the Central Valley, are going to truck and net pen rear 30 million Chinook salmon smolt this spring. The first loads of small salmon were delivered to Rio Vista and released into the Sacramento River on Monday, March 24 and the project will continue into May.

Salmon taking the quick ride from tanker truck to the protective custody of the net pens

I’m a huge supporter of this and figured I’d give you a little background…

Out-migrating hatchery Chinook salmon smolt from California’s Central Valley rivers have to navigate a seemingly impossible list of hazards that include massive water diversions, predators at every turn, poor water quality and temperatures that are often 70 degrees and higher. In a low water year like this, the trip is exponentially more lethal.

FFC biologist James Walker oversees the offloading of Chinook smolt from the tanker trucks to the net pens. On this day, the pens received approximately half a million fish. The transfer of the fish from the DFW’s trucks to the pens takes close to and hour.

To help increase the odds of the little salmon’s survival, the California Department of Fish & Wildlife has been engaged in trucking the fish to locations in the lower Sacramento/San Joaquin Delta and upper San Francisco Bay for decades. The ride down Interstates 5 and 80 from the hatcheries on the Feather, Mokelumne and American rivers has given the fish a fighting chance but the feds, who operate Coleman National Fish Hatchery on the Sacramento River, have been more concerned with straying than salmon survival and have not participated. This year, however, the Golden Gate Salmon Association presented compelling evidence that the loss of salmon dumped directly into the river would be catastrophic and the feds finally agreed.

But simply trucking the salmon doesn’t ensure their survival — dumping the smolt directly into the water (like planted trout) made it so that predators like striped bass, sea lions, terns, seagulls, cormorants, etc. had plenty of food to eat. It was pure carnage at the release sites as the dazed fish suffered heavy losses immediately after leaving the trucks.

Immediately after hitting the water in the pens, the Chinook are dazed and confused. Most flounder around on the surface…and it is here where you can really see the benefits of the “protective custody” that the net pens provide. It’s estimated that at least 20% of the smolt are lost to predation from birds during this vulnerable period. In as little as 20 minutes in the pens, however, the fish get their wits about them and start to school up.

Fishery Foundation of California, which 20 years ago saw a better way…

According to the Foundation’s Executive Director, Trevor Kennedy, the FFC funded the area’s first net pen acclimation pilot study. They found that the net pens worked…big time. In fact, surveys showed that survival rates to the ocean for Chinook acclimated in the pens were 400% higher than those simply dumped straight into the river.

Think about that for a second…four hundred percent better survival! When you’re talking about that kind of improved survival for the tens of millions of fish released, you can see what a profound impact such a simple project can have!

Once the fish are all loaded up and acclimated to their new surroundings, the pens are covered in netting to protect from bird attacks, the lines are cast off and the whole unit is towed to the release site.

After that, the project got the green light to go full bore and the numbers are impressive. The amount of fish that are released via the net pens varies annually, but Kennedy says that his outfit typically does 60 to 70 percent of the State’s Chinook…and are doing all of them in 2014!

Initially, the funding came from mitigation money from the water contractors for the zillions of smolt they sucked up in their pumps. Then, money for the project came from the Commercial Salmon Trollers. Kennedy said that for the past 6 years, the funding has come from Bay-Delta Fishery Enhancement Stamp. Unfortunately, future sources for this program are unclear…but it obviously needs to be continued!

James Walker and Kari Bur pulling the net at the release site and sending the little salmon on their way..

The downside is the DFW and Feds would prefer to release fish in the river instead. They have this huge concern about salmon straying into the “wrong” systems. But, come on folks…in the Central Valley, which has been so altered by man, there’s nothing natural left. In this day and age, a live salmon in a river is a good salmon…regardless of origin.