Article covering the 2021 Fall-run salmon spawn.

Found this blog to be quite interesting regarding our inland fisheries.
I book marked it to read some of the articles.

https://calsport.org/fisheriesblog/

Authored by:

- Tom Cannon an estuarine fisheries ecologist and biostatistician for more than 35 years.
- Dave Vogel a fishery scientist with 40 years experience.
- Don Bayer a retired fisheries biologist who has worked over 40 years on salmon biology and management from California to Alaska.

The most recent article covers the 2021 Fall-run salmon spawn.

Scientists knew going into this year that water temperatures were going to negatively impact both the winter- and fall-run Chinook on the mainstem Sacramento. Without major infrastructure improvements at Shasta, this will not get any better when we have years of prolonged drought. Good news is that the early storms allowed fish into the upper Sacramento tributaries. Churn, Cow, Clear, Middle, Battle, and even little Salt Creek had tons of salmon in them. The smell on Clear Creek this fall was reminiscent of Alaska. I would not be surprised if more fish ended up in Clear Creek than the mainstem above Clear Creek.

Dropping the flows in the fall is the standard practice of Reclamation. Several agencies document the redd dewatering and stranding that occurs throughout the season. Relatively few (<5%) of redds are dewatered and it is generally too early to strand significant numbers of juveniles. To me this is just an issue of public perception, I do not think redd dewatering and stranding are major issues to the recovery of salmon.

I have major issues with their turbidity assessments. First off, 7 NTUs is nowhere near lethal (or sublethal) for any salmonids. If it was, salmon wouldn't exist (think visibility of glacial rivers in AK/BC that support salmon). Secondly, the relationship between turbidity and total suspended sediments (TSS) is not comparable. Turbidity measures light absorption while TSS measures physical sediments in the water column. These two measurements are inherently related but you can't just take a turbidity measurement and assume TSS levels. I was curious and went back to check some of the data I collected while in grad school. The relationship between turbidity and TSS in my samples was about 3 NTUs:1 mg/L TSS but varied from less than 1:1 to 7:1. Even chronic turbidity issues would need to be in the hundreds/thousands before you would expect lethal or sublethal effects according to the source they provided. Turbidity is going to be an issue for the next several years as all that ash and silt from the fires makes it down the system.

Hi Fishtopher, Thanks for commenting, it is always good to hear from another source.

I believe that the NTU level in the graph was referring to egg suffocation not lethal NTU levels for full grown salmonoids. I say that because it read "Red line depicts literature-based, severe-mortality turbidity level for eggs and embryo salmon for a one-day exposure." My understanding is that eggs and embryos have a much lower tolerance than their parents to siltation issues especially if it it covers or sticks to their egg sack. Is that correct?

I have noticed that the majority of the Salmon in Alaska are spawning in clear water tributaries as opposed to the larger glacier melt rivers perhaps that is why? Do you have insights in to that? Otherwise I totally agree that full grown salmon that use the glacial river to get to their clear water tributaries would probably never get to spawn if they had to wait for the turbidity levels to drop to very low levels before they made their way upstream. I was fishing tributaries of the Susitna river in Alaska for the last few years and there was a marked difference between the turbidity of the tributaries versus the main river.

I found this article below that discussed turbidity and its relationship to eggs and its relationship to young and to full grown fish.
http://www.krisweb.com/stream/sediment.htm kind of interesting.

There were several articles I also read but none of them really discussed a direct correlation to NTU or TTU levels. Mostly they discussed silt in terms of size and ppm or mg/l. Seems in the articles that I read that most had a consensus that if more than 13% fine sediment (<0.85 mm) intruded into the redd, almost no steelhead or coho salmon eggs survived. Not sure how that relates to TTU, NTU or TSS but I assume that perhaps you have some understanding of how % of fine sediment relate to those items?

I ask because I realize you have more knowledge in this area than I do and I do like to read about different scientists ideas and findings in regards to Salmon, Steelhead and Trout survivability. I actually learned in one article that Steelhead eggs emerging to their larval or fingerling stage can handle emerging from silt in the redd better than Salmon due to the shape of their heads and that was kind of interesting.

Another article that covered a lot of ground regarding siltation and ash issues as it relates to migration, reproduction, juvenile salmon, grown salmon, brown trout, lake trout, issues and more which included charts on many different study findings here:https://www.wsdot.wa.gov/research/re...orts/526.1.pdf

Thanks for bringing this topic up it gave me something to research instead of researching new fly lines or the latest gear.

Regards,
Tim C.

Quote:

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Originally Posted by tcorfey

I believe that the NTU level in the graph was referring to egg suffocation not lethal NTU levels for full grown salmonoids. I say that because it read "Red line depicts literature-based, severe-mortality turbidity level for eggs and embryo salmon for a one-day exposure." My understanding is that eggs and embryos have a much lower tolerance than their parents to siltation issues especially if it it covers or sticks to their egg sack. Is that correct?

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Eggs are definitely the most sensitive to sedimentation. Generally the most impactful sediments on eggs would be in the coarse sand to very fine sand/coarse silty ranges.

Quote:

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Originally Posted by tcorfey

I have noticed that the majority of the Salmon in Alaska are spawning in clear water tributaries as opposed to the larger glacier melt rivers perhaps that is why? Do you have insights in to that? Otherwise I totally agree that full grown salmon that use the glacial river to get to their clear water tributaries would probably never get to spawn if they had to wait for the turbidity levels to drop to very low levels before they made their way upstream. I was fishing tributaries of the Susitna river in Alaska for the last few years and there was a marked difference between the turbidity of the tributaries versus the main river.

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Salmon spawn in both clear water tributaries and in glacial rivers. There are plenty of rivers with turbidity due to glacial runoff in BC and AK that support salmon. Many Copper River tributaries are heavily glaciated but still support huge runs of salmon. Even the mainstem Susitna supports salmon although the clear water tributaries are definitely productive as well.

Quote:

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Originally Posted by tcorfey

I found this article below that discussed turbidity and its relationship to eggs and its relationship to young and to full grown fish.
http://www.krisweb.com/stream/sediment.htm kind of interesting.

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That website is a great resource. I actually work with several of the authors that are referenced on that site.

Quote:

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Originally Posted by tcorfey

There were several articles I also read but none of them really discussed a direct correlation to NTU or TTU levels. Mostly they discussed silt in terms of size and ppm or mg/l. Seems in the articles that I read that most had a consensus that if more than 13% fine sediment (<0.85 mm) intruded into the redd, almost no steelhead or coho salmon eggs survived.

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I definitely agree with that statement but keep in mind the different sizes of particle sizes that could contribute to turbidity. Usually turbidity is caused by sediments that are suspended. Particle sizes that are approaching 1 mm ('fines' in the krisweb site) aren't likely to be in suspension. Things like glacial runoff or fire ash that are in suspension are in the micrometer ranges or 0.001 mm. Particles of that size are unlikely to settle out in an area where a redd would be present as it would be immediately transported downstream due to the high river velocity. This is why I have major issue with the blog post equating turbidity to lethal egg mortality. The fact that turbidity was traveling through the low-velocity lakes meant that any sort of sediments that could be potentially harmful to eggs were likely settling out and the only stuff left was the very fine ash and clays that stay in suspension and would be transported through the system.

Hope this helps.

Fistopher, that is excellent info, thanks for the follow-up. :)