Since you’ve got current data on striper abundance for 2009, let’s look at the entrainment data for 2009. Follow this link:
https://nrm.dfg.ca.gov/documents/Con...vageMonitoring
Download the report entitled: “2009 Fish Salvage at the Tracy Fish Collection Facility”
Download the report entitled: “Fish Salvage at the SWP and CVP Fish Facilities during 2009”.
First let’s discuss some generalities and trends. Notice first that you’ve got the entrainment data going all the way back to 1982. Hence my comment that there are decades worth of empirical data. Notice that the numbers are completely time weighted to account literally for every minute the pumps are running in the TFCF report. Also notice that entrainment was much higher in the first 5 years of entrainment monitoring for Chinooks, but it dropped off quite sharply after that. Seems the powers that be made it a priority to improve efficiency. Also notice that the pumps tended to entrain more streamborn fish, than hatchery fish. For the sake of simplicity, we're just going to look at this in terms of abundance.
Can’t say I’ve ever heard any concern from you or your cohorts over things like carp, bluegill or catfish, so let’s stick with the species that you and your cohorts are always attempting to shift the predation impact of stripers to something else: Chinook salmon. Take note of how loss and salvage are defined for Chinook in the Tracy report. All that said, let’s see if the actual data supports “The pumps are the real predators” mantra.
Let’s attempt to establish some facts and make some assumptions.
The caveat with the entrainment data is that larval fish under 20mm in FL are not reliably entrained and actual losses for anything <20mm FL is likely understated. Chinooks that are mature enough to undergo the smoltification process and are down migrating through the Delta are all definitely going to be in excess of 50mm in FL. In other words, Chinooks are plenty big enough to be entrained, and thus there’s no good reason to think the numbers for Chinook are understated.
Let’s assume that salvage survival is 0.0%. In other words, we’re assuming that every Chinook that is processed dies. If it becomes entrained, it’s gone. This assumption is extremely biased in favor of the pumps being the real predators.
Let’s also assume that there is NO predation of Chinook, by any striped bass that are less mature than age3+. Age 3+ stripers are defined in the abundance modeling as being >460mm FL. So all those Chinook that got eaten by stripers 459mm FL or less in 2009, don’t count. Call it a big mulligan. This assumption is extremely biased in downplaying the predation effect of stripers.
Let’s also assume that 2009 was a funky year in terms of abundance sampling for striped bass. And the actual abundance falls in the lower range of the 95% confidence levels of the Petersen model. I’m assuming the number you quoted was the median here, so we’re going to purposely reduce the number you provided to 800,000 age 3+ stripers. Again, this assumption is also extremely biased in downplaying the predation effect of stripers.
Here’s the actual numbers:
Chinook numbers from Skinner ran 2463 and 10620 respectively for salvage and loss.
Chinook numbers from Tracy ran 4666 and 3682 respectively for salvage and loss
Here’s what you end up with: 2463+10620+4666+3682= 21,431 Chinooks killed by the pumps. Again we’re assuming no salvage survival. They’re all dead and removed from the equation. That number still seems pretty insignificant though doesn’t it? What percentage of the total abundance does that number really represent? Hatcheries in the system typically produce~26-30 million or so Chinook each year if memory serves. Let’s assume 2009 was a horrid year for hatchery production and they only produced 20M Chinooks (I forgot to lookup the actual hatchery production for 2009, but even in a year where the SFRC collapse was in effect, I don’t recall any issues with hatcheries hitting their production quotas for 2009, so I’m fairly certain 20M understates actual production for 2009). To five sig figs, that comes to 0.00107 or 0.107%. In other words, the pumps killed~ one tenth of one percent of the hatchery production for 2009. Add in the natural Chinook production, that number becomes even more insignificant.
This is the point where I actually picked up the phone and made a call because I “knew” there was something I had to be overlooking or not understanding. I definitely didn’t expect the data to support the “pumps are the real predators” mantra, but I did expect to see data that indicated the pumps were pulling in something like 500k to 1 million Chinooks a year on average. That’s not what’s happening Mike. Those are the real numbers, and I was told that there’s no other way to validly interpret those numbers, and that they are indeed time weighted to the minute, as the equation indicates.
How does that stack up to predation by stripers? It falls well short as you might imagine. For predation by the stripers to equal the “bodycount” entrained by the pumps, if only 3 (and I’m rounding up here from 2.7 to 3) out of every 100 age 3+ stripers ate one single, solitary Chinook smolt during 2009, predation by stripers equals the effect of the pumps. If 6 out of every 100 stripers ate 1 Chinook, they’ve doubled the predation effectiveness of the pumps. If 30 out of every 100 age 3+ stripers at 1 Chinook, they’ve magnified the predation effect of the pumps 10 fold. And remember, we’ve made assumptions that purposely understate the number of stripers capable of preying on Chinooks, and assumptions that inflate the number of Chinooks removed by the pumps.
Now I’m not arguing that predation by stripers is having a population level effect on Chinooks, but the potential for Chinooks to become entrained by the pumps ends once the fish make it downstream of the pumps. Predation by stripers doesn’t stop even long after the Chinooks hit the salt. That as I see it, is the reality.
But there has to be some other systemic effect that’s magnifying the effect of the pumps but it’s not showing up in the data, right? Let’s allow for that and build in a safety factor. It’s not actually the pumps but things like the configuration of the conveyance system causing more ideal predation hot spots (things like CCFB, and RBDD), a river that in its lower reaches runs levee to levee with no feathered edges, etc. In other words, the Chinooks are getting eaten by stripers and other predators, but we’re placing that predation blame on man-made structures that create unnatural predation opportunities. What do you think is fair? 10 percent? 50 percent? One hundred%? Well at 100% we move that number from 21k to 42k. Still seems pretty insignificant doesn’t it? Let’s just toss objectivity aside and totally cook the books and see how much you have to purposely skew those numbers for them to become significant. Let’s build in a safety factor of 4000%, critics be damned that there’s no remotely justifiable reason for doing so because we’re going to do whatever it takes to make those numbers seem significant. That gets us to 878,671. That has to be significant right? We’re approaching a million dead Chinooks. But is it significant?
If every age 3+ striper (keep in mind we’ve already done a lot of cooking by purposely reducing the number of stripers large enough to prey on Chinooks) eat only an average of 1 chinook for the entire 365 day period, the pumps and the stripers are running pretty close to even. And it doesn’t matter whether those Chinooks are being eaten upstream of the delta, in the bay, or in the salt off the Farallones. Do you really think age 3+ stripers are actually only eating one Chinook a year on average?
Maybe 2009 was just a really low year for entrainment. Truth is, it was. Run another year where the entrainment numbers are higher. Run another species of concern (steelhead, or D Smelt). Keep in mind those as you go back in time, striper abundance begins to also rise and other factors come into play, and you need to take those factors into account.
So I’m asking, do you think the data supports the “pumps are the real predators” mantra?
Striper Stuff Redux....
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Originally Posted by ycflyfisher
"Da Pumps"
So, probably not going to be any rallying cry for indirect impacts.
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