By Don Wright
A few years ago I was sitting in the boardroom at the Lower Tule River/Pixley IDs’ headquarters in Tipton attending a South Valley Water Association meeting. There was a presentation given by Doug Demko of Fishbio on salmon in the San Joaquin/Sacramento Delta. Demko was saying things I’d never heard before about salmon survival rates and the role predation plays. The difference between Demko’s presentation and the usual Delta 
update was as great as the difference between Rush Limbaugh and Sean Hannity. While I often agree with Hannity’s assessment of a given situation – say, the irony that a group purporting to fight fascism is the closest thing to Brownshirts running rampant on Kristallnacht we’ve seen in this country – I don’t learn much from him. Limbaugh on the other hand gives a little background and I at least learn a little about his reasoning on the subject. (If Limbaugh and Hannity make you uncomfortable in this time of brittle political sensibilities feel free to substitute Maher and Maddow.) What I’m getting at is we all know there are problems with salmon in the Delta but Demko gave some reasoning on the subject and didn’t just complain about it.
So what was the great revelation I’d never heard before? Ninety percent of the out migrating juvenile salmon are eaten by predators before they ever get to the ocean. Not just any predators. The main culprits are non-native sport fish such as stripped bass.
Many times we in the Valley hear a great deal about how water exports for agriculture is the great destroyer of the Delta ecosystem. If we’d just stop sending water to farms the endangered and threatened species would have a fighting chance. There is a remarkable lack of editorializing about cutting back exports to urban centers. It’s a given they need lawns and golf courses and swimming pools. But I digress. Even if the editorial boards of the major news outlets and the social justice warriors don’t begrudge nonessential urban water use they have been focused on reducing exports for agricultural use as the panacea for all the Delta’s ailments.
Turns out even Sacramento, the state capital was dumping waste into the waterways. It wasn’t untreated, it was just not treated enough. Dilution is still seen as a viable way to deal with waste water. At least that’s on the table now as another stressor to the Delta’s health. Drive through Stockton on I-5 and there is a port to the west of downtown. Ocean going ships are docked there. They draw a draft deeper than the natural channel so there had to be a path dredged. The deeper channel resulting from dredging caused an anaerobic condition that prevent salmon and other fish from navigating its course.
Before my friends in the Delta, Sacramento and the non-law firm environmentalists groups get upset let me state this; I’m proud we can ship Valley produce out of the Port of Stockton. It was better to place aeration devices in the deep water channel than close the port. To the folks in Sacramento I understand dilution is an efficient and economical means to deal with sewage. But the urbanization from the Golden Gate to Roseville has brought its stress to the Delta and dilution may not be able to keep up with the increased waste. Finally the Bay Area has to import surface water to meet its needs and before throwing any brick it may want to consider if its house is made from stone or glass.
The Delta also has a lot more people living and recreating there. That brings us back to the non-native predators. The salmon have advocate groups supporting them. The stripped bass have advocate groups supporting them. (I’m I alone in finding it strange that biggest killer of salmon in the Delta has a cheerleaders? I’m I also alone in finding it strange the folks who depend on salmon for a living, like commercial fishermen are largely silent on predation in the Delta but are very loud in the antiexport chorus?) More people with access to the Delta have brought about yet another stressor – non-native aquatic plants. Someone dumps their home aquarium and bam – a new, non-native stressor is introduced. Hyacinth is such a problem mechanical harvesting is necessary just to clear a path in the Delta river ways. Boating is impacted. I guess if you had one of those air boats like they use in the Everglades you could just skim across the top.
All of the above to say Demko and company have come up with some observations worth keeping in mind when discussing the stressors in the Delta. Check out Fishbio’s Monday, November 2, 2020 “The Fish Report.” https://fishbio.com/field-notes/the-fish-report/weeds-invasive-aquatic-plants-can-increase-juvenile-salmon-predation-risk
This report states, “Predation has been posited as the primary cause of juvenile Chinook mortality in the Delta. Not only are non-native predators abundant, but predation risk may be compounded by the increasing prevalence of invasive aquatic vegetation such as Brazilian waterweed (Egeria densa). These non-native plants may deal a double blow to Chinook by both restricting their access to formerly open-water habitat and by providing predators like largemouth bass (Micropterus salmoides) an edge in a habitat they are well-adapted to. Notably, the abundance of largemouth bass in the Delta has increased alongside the proliferation of invasive submerged aquatic vegetation.”
Fishbio is easily one of the most interesting and creative biology consulting firms you can find anywhere. And please, when I say creative I don’t mean in the shady bookkeeping sense; I mean the men and women there design and build innovative equipment that furthers the technology and the science. They even brew their own beer and post some off the wall stories like can a swordfish take a shark? Go to their website and find out yourself, I won’t be a spoiler.
Once in a while one stumbles upon some light in the murk. Fishbio does shine some light, refreshingly follows facts to conclusions as opposed to allowing emotions to infiltrate science. They have a free newsletter I found worth adding to that trash can of an email inbox I sort through. Amazingly Fishbio explains science in a way I can understand. Water is counter intuitive and Fishbio helps me get a fresh take on things; maybe even think a little deeper. Pun intended.
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