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  • #16
    Toccoa River Temp Update

    My son and I took a road trip and here is our findings. These temps were taken between 6:45 and 7:45 pm this evening.

    Tammen Park 70.4
    Curtis Switch 74.8
    Horseshoe Bend 75.3

    Readings were taken with a digital stream thermometer.

    No dead fish seen.

    Comment


    • #17
      Did an Adopt-A-Stream monitoring session today at Hogback, one before the generation began and one afterwards (the only thing that changed was the air temp. and cfs.), and recorded the following data:

      Date: Aug 16
      Time 11:00 A.M.
      DO 8.4 ppm
      Water temp. 22 c (71.6 f)
      Air temp. 26c (78.8f)
      Flow 137 cfs

      Date Aug 16
      Time 3:00 p.m.
      DO 8.4 ppm
      Water temp 22 c (71.6 f)
      Air temp 31 c (87.8 f)
      Flow 1653 cfs

      Water stained much more than normal.



      A question I have for some of you more scientific-minded folks: It's my understanding that the amount of dissolved oxygen (DO) water can hold decreases as the temperature increases (colder water can sustain more dissolved oxygen than warmer water). If I understand correctly, trout might not survive lengthy periods of 75 degree f. water, but its not a direct result of being exposed this temperature per se, but because they suffocate from the decreased oxygen that 75 degree water contains -- Is it the DO levels, not the temp. that gets them? On the Toccoa tailwater, we've seen the temps rise substantially during the past week (from 64 f to over 71 f) but the DO levels have remained constant at a little over 8 ppm at Hogback. So can the oxygen infusion system at the dam keep the DO levels high enough for the fish to survive higher temps than would be possible in natural free-flowing stream?

      -- J Pool

      Comment


      • #18
        Originally posted by Dragonfly Man View Post
        A question I have for some of you more scientific-minded folks: It's my understanding that the amount of dissolved oxygen (DO) water can hold decreases as the temperature increases (colder water can sustain more dissolved oxygen than warmer water). If I understand correctly, trout might not survive lengthy periods of 75 degree f. water, but its not a direct result of being exposed this temperature per se, but because they suffocate from the decreased oxygen that 75 degree water contains -- Is it the DO levels, not the temp. that gets them? On the Toccoa tailwater, we've seen the temps rise substantially during the past week (from 64 f to over 71 f) but the DO levels have remained constant at a little over 8 ppm at Hogback. So can the oxygen infusion system at the dam keep the DO levels high enough for the fish to survive higher temps than would be possible in natural free-flowing stream?
        Great question, Mr. Pool! Looks like maybe you are on to something here. Here is some information I found from a group sponsored by the State of Wisconsin DNR and Univerity of Wisconsin.

        Both plants and animals depend on dissolved oxygen for survival. Lack of
        dissolved oxygen can cause aquatic animals (e.g. fish,macroinvertebrates) to quickly leave the area or face death. Under low oxygen conditions, the
        aquatic animal community changes quickly. Under extreme conditions, lack of oxygen can kill aquatic plants and animals. Measuring dissolved oxygen is probably the most significant water quality test to determine the suitability of a stream for fish and many other aquatic organisms.

        Different aquatic organisms have different oxygen needs. Trout and stoneflies, for example, require high dissolved oxygen levels. Trout need water with at least 6 mg/L D.O. Warm water fish like bass and
        bluegills survive nicely at 5 mg/L D.O. and some organisms like carp and bloodworms can survive on less than 1 mg/L D.O. The oxygen demand of aquatic plants and cold-blooded animals also varies with water temperature. A trout uses five times more oxygen while resting at 80° F (26.7° C.) than at 40° F (4.4° C).


        Aquatic plants produce oxygen by photosynthesis during daylight hours but they also use oxygen for respiration. During the night or on heavily overcast days, respiration removes oxygen while photosynthesis stops or
        drastically slows down. Oxygen depletion can occur because of heavy plant growth. Complete depletion of D.O. can sometimes be detected
        with your nose. Anaerobic decay results in a rotten egg smell (hydrogen sulfide gas)

        While fishing on Saturday, there was definitely a faint smell described above but, nonetheless, your DO findings appear encouraging anyway! I actually had a pretty productive day on Saturday catching about a dozen or so with most going 12 to 14 inches. They appeared rather healthy, too. Even though I got 'em in quick and didn't even lift them out of the water when removing the hook, all of them swam away quickly.

        Those that know me know that I am definitely not "scientific-minded" by any stretch of the imagination, but it sure looks like, just by doing a little reading, that the recorded DO levels found in these measurements sure can't hurt anything. I wonder what a night-time measurement might show when the photosynthesis stops? (hint, hint, Mr. Pool ) I guess it's OK to find a little hope in positive DO levels, right?

        Comment


        • #19
          Update and Fishing Recommendations with high temps

          Yesterday, I received this information from John Damer (GA DNR Fisheries Biologist):

          Our last data exchange covered up to midnight on Tuesday night 8/10. At that point water temps recorded at the dam had just crossed the 20*C mark. Still no change in the rate of water temperature increase. But, this was before TVA slowed down their average daily discharge rates, and we may still experience some cooling effect (or at least a decease in the rate of warming) from that. We will receive a new week's worth of data this Thursday, and will know more then.

          One thing you can help with is to remind anglers that catch-and-release mortality can be high when temperatures hit 70*F and above. Here are just a few suggestions for folks who intend to fish the tailwater or other streams that are getting warm.
          1) Fish with heavier line/tippet than normal. You may not hook as many fish, but that 24" inch bow is going to take "hours" to land on 7x tippet, and probably won't last long if you plan to release it.
          2) Along the lines of #1, don't overplay the fish. Often the most exciting part of catching a fish is feel them tug on the end of your line. Some anglers (especially less experienced ones) tend to keep the fish on for A LOT longer than needed to extend that experience. I watched an angler last week at Tammen Park play a 14" brown for three or four minutes while his rod was barely bent. I estimated that a more experienced fisherman could have hooked, played, landed, and released two or three fish of similar size in that time (if the fish were willing to bite, of course).
          3) Keep pictures and handling time to a minimum. The fish are already stressed from the high temps and the fight you just put them through. Leaving them out of the water to get that perfect shot for your desktop background may make the difference between life and death for the fish.
          sigpic

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          • #20
            Great information, Becky. Thanks for posting. Here is some more information that came across my email from someone that has some good knowledge of trout in response to Dragonfly Man's earlier question. This is encouraging.

            Your understanding of the relationship of DO concentration and water temp is correct. We can manipulate that relationship (to a degree) by infusing pure oxygen. The infusion system in the lake is the same method that we use to maintain acceptable DO levels in our transport tanks. 8 ppm in the river is encouraging! My trout are very happy at 8 ppm, however we do try to minimize any conditions that cause stress. Trout are susceptible to stress induced illness and some of the pathogens are more active at higher temps. If I could choose a water temp for my hatchery it would be 58 degrees F. If you catch trout in these stressful conditions, try to release before they are exhausted. Again, 8 ppm DO in the river is good news! Keep those tiny bubbles rising!

            Comment


            • #21
              I have a friend that lives on the river below Horseshoe Bend. He said as of late (I talked to him yesterday), he has observed numerous dead trout washing by his place. He is kind of at the end of the line so he could be seeing fish from all over. Some were “nice size”, he said. Not good……….

              Do we need to start talking about restoration at this point. How much luck are we going to have getting TVA to foot the bill? We need to have a plan in place! Could be a floating stocking so the fish would not be concentrated at the regular “meat holes” and would have a better chance of carry-over….
              Last edited by clewis1014; 08-18-10, 03:21 PM.
              "We are masters of the unsaid words, but slaves of those we let slip out”

              - Sir Winston Churchill

              Comment


              • #22
                dead fish

                clewis,

                See if you can get your hands on some photos of those dead fish. It's too soon to give up on the river. It is a river on the brink and we can still push it the right way. The slower draw-down and increased oxygen still gives us hope. All we need is to hold out untill the weather cools a bit. TU, the DNR, and the local paper and citizens have been giving the TVA an earfull. TVA's most recent statement said that there has been no evidence of trout being harmed by the current drawdown. A dead fish pic would go a long way on the front page of the paper up here.

                Bill O.


                _______________
                www.oysterbamboo.com
                www.oysterbamboo.com

                Comment


                • #23
                  I will see what I can do. This guys is in a bad spot professionally and may not/ could not take them for me but would let me take them. Lets put out some feelers to other members soliciting honest pics of tailwater fish kill. If the TVA is playing games, screw them!

                  “Wanted”
                  Honest, un-staged photos of dead fish from water temp rise due to lake draw down on the Toccoa tailwater.

                  Please include:
                  Date and time of pic (digital stamp would be best).
                  Location
                  Water temp if available
                  Author of pic (optional)

                  Please email pics and short narrative of how fish was located to ___________.
                  "We are masters of the unsaid words, but slaves of those we let slip out”

                  - Sir Winston Churchill

                  Comment


                  • #24
                    Water temp at Hogback yesterday was 73 at 5:30pm with full generation.

                    Comment


                    • #25
                      Looks like the break in generation is over. Turning the jets back on tomorrow and Sat.

                      Comment


                      • #26
                        I spoke to the Regional Director of American Rivers today in Columbia SC. I explained our situation here and the TVA moving forward with the draw down in spite of the DNR recommendation to wait.

                        It looks like they are very interested in what is happening here. Check out the link below. This organization has had tremendous success in dealing with Hydo Electric Fisheries like the Tail Waters. They are excellent at finding the chink in the armor. I am asking for consultation from them at this point.

                        We have a meeting tomorrow at Unicoi Outfitters to discuss this topic among others. This near tragedy or maybe still to be tragedy may be our opportunity to make some great progress with this fishery. I agree with Bill O 100%. We need evidence. Start taking as many photos as possible.

                        Trout Addict - Duane Miller

                        www.americanrivers.org

                        Comment


                        • #27
                          Originally posted by Trout Addict View Post
                          I spoke to the Regional Director of American Rivers today in Columbia SC. I explained our situation here and the TVA moving forward with the draw down in spite of the DNR recommendation to wait.

                          It looks like they are very interested in what is happening here. Check out the link below. This organization has had tremendous success in dealing with Hydo Electric Fisheries like the Tail Waters. They are excellent at finding the chink in the armor. I am asking for consultation from them at this point.

                          We have a meeting tomorrow at Unicoi Outfitters to discuss this topic among others. This near tragedy or maybe still to be tragedy may be our opportunity to make some great progress with this fishery. I agree with Bill O 100%. We need evidence. Start taking as many photos as possible.

                          Trout Addict - Duane Miller

                          www.americanrivers.org
                          Nice job Duane!

                          I checked the river temps this morning below hemptown (72 deg.) and Tammen Park (71 deg.) during no generation. With the recent rains washing the dry banks of Lake Blue Ridge, the river was really muddy. In fact, it was the first time I've seen the water really muddy right below the dam. I saw at least a half dozen guys fishing at Tammen despite the conditions and watched them pull in at least a half dozen fish - all fingerlings. Anyway, keep those reports coming!




                          Bill O.


                          _______________
                          www.oysterbamboo.com
                          Last edited by oyster; 08-19-10, 10:13 PM.
                          www.oysterbamboo.com

                          Comment


                          • #28
                            Originally posted by Dragonfly Man View Post
                            A question I have for some of you more scientific-minded folks: It's my understanding that the amount of dissolved oxygen (DO) water can hold decreases as the temperature increases (colder water can sustain more dissolved oxygen than warmer water). If I understand correctly, trout might not survive lengthy periods of 75 degree f. water, but its not a direct result of being exposed this temperature per se, but because they suffocate from the decreased oxygen that 75 degree water contains -- Is it the DO levels, not the temp. that gets them? On the Toccoa tailwater, we've seen the temps rise substantially during the past week (from 64 f to over 71 f) but the DO levels have remained constant at a little over 8 ppm at Hogback. So can the oxygen infusion system at the dam keep the DO levels high enough for the fish to survive higher temps than would be possible in natural free-flowing stream

                            -- J Pool
                            Yes, you are correct on the Temp/DO relationship. As water temp rises, its abilty to absorb oxygen (and other gases from the atmosphere) decreases.

                            I would like to know what type of DO tester you are using. From what I know about water chemistry, a temp swing from 64 to 71 should reflect a change in DO.

                            J Byrd
                            "All things being equal, the simplest explanation is usually the correct one."
                            -Occam's Razor

                            Comment


                            • #29
                              Not good!

                              Saw at least a 22 incher float by my place today just as the generation started- dead as a doornail! No camera but my phone and it was too far away for a decent picture. Spoke with a couple kayakers who said they saw 4 or 5 good size fish dead as well. So are the big ones the first to go in the chain of events?

                              Comment


                              • #30
                                Critical Thermal Maximum

                                Here is part of a response from John Damer when asked about water temperatures and dissolved oxygen on the river:

                                Thanks John for the information!

                                The interactions between water temp, DO, and trout are very complex, but for the most part you are both right. When the water temp goes up, the water cannot hold as much oxygen as it did at cooler temperatures. Here is a table I found on the internet that illustrates this point.

                                Relationship Between Temperature and Oxygen Solubility

                                Temperature(degrees C) Oxygen Solubility(mg/L)

                                0 14.6
                                5 12.8
                                10 11.3
                                15 10.2
                                20 9.2
                                25 8.6

                                Keep in mind that trout usually require at least a DO concentration of around 5-6 mg/L for survival at "normal" temperatures. Notice that all the way up to 25*C (or 77*F), water has the capacity to hold that level of DO and more (up to 8.6 mg/L according to the chart). But, the metabolism of a trout also increases at higher water temperatures, increasing its oxygen demand above that 5-6 mg/L level to some degree,say to 7 mg/L at 25*C (just a guess, since I am having trouble finding any research that actually tells me how oxygen demand of a trout changes with temperature). We are getting close to that 8.6 mg/L, but still not there.

                                Now, in a river there are lots of things living in the water (fish, invertebrates, bacteria, plankton, etc.). These living things are using oxygen for respiration. In a typical stream, this keeps the actual dissolved oxygen level lower than what it potentially can hold. This is especially the case when the water is slow moving (pools, eddies), as opposed to faster water where new oxygen from the air is being mixed-inall the time (riffles, cascades, etc.). Also remember that the low flows that usually occur with high temps also mean less of this mixing.
                                So, to answer the question asked by John "Is it the DO levels, not the temp. that gets them?", for a natural free-flowing system the answer is,Yes. Low flows, high temps, and low DO concentrations usually occur together in the wild and contribute to the death of trout, but the ulitmate factor that is directly responsible is probably most often dissolved oxygen.

                                Of course we are not talking about a natural system on the Toccoa tailwater!

                                By injecting pressurized oxygen into the forebay of the reservoir, TVA can keep DO levels artificially high; at or even above what was listed in the chart shown above (supersaturation). It is our (DNR's) hope that TVA will be able to keep those DO levels elevated enough with their oxygen injection system that mortality will not occur as a direct result of low DO.

                                Just like every other fish, trout have a Critical Thermal Maximum (CTM). Simply put, this is the maximum temperature that a fish can tolerate before it becomes disoriented, loses its ability to swim upright, and ultimately dies. The CTM is different for each species, and even for individuals within the same species. CTM also depends on what temperature the fish is acclimated to, how quickly the temperaturei s raised, and on any number of other stressors. This makes measuring CTM very difficult, and when you can accurately measure CTM under one set of circumstances it may be different under another. With all that being said, CTM for rainbow and brown trout are usually reported as being somewhere in the mid to high 70s (F). Brook trout are less tolerant, with CTMs in the low to mid 70s.
                                Last edited by Becky Hulsey; 08-20-10, 07:29 PM.
                                sigpic

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