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Thread: Fish counts....?

  1. #1
    Moderator AKmud's Avatar
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    Default Fish counts....?

    I noticed on the AOJ website that the Deshka is showing 11 silvers through the weir already. This is somewhat perplexing for me. There are still lots of kings in the water (well below the weir) so how does the counter tell the difference between a silver and a small king as it swims by? I have never thought about this before, but I thought the counter was an automated system or is there a person physically viewing what is happening there?

    Someone please enlighten me....

    Link to the AOJ Deshka Coho count -

    http://www.alaskaoutdoorjournal.com/...eshkacoho.html
    AKmud
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    The porcupine is a peacful animal yet God still thought it necessary to give him quills....

  2. #2

    Default

    The fish are trapped in a box at the weir. A physical count is taken by a fish and game employee and then the box is opened for the fish to continue upstream. I have serious reservations about this method, as it puts a lot of stress on the fish, as evidenced by the number of dead fish below the weir. It has also changed the spawning patterns of the kings. There are now kings spawning below the weir. That used to never happen, but then again, it could be that all the pesky boat traffic has changed the river depths below this point <grin>. We are also paying long term disability to some of the employees that have gotten "hurt" messing around with the weir set up. Seems as though an aerial count upstream for kings and a sonar for all other species would suffice, but hey I ain't no biologist. At least the bios have quanitifiable data now, to use for their management purposes.

  3. #3

    Angry weirs

    Good question, I was wondering the same myself.

    About 10 years ago or so a weir was placed right after the flats on Jim Creek. The fish would back up so thick they would get beached and dozens of salmon would be flopping on sand bars at any given time. I wouldnt doubt if I could have counted hundreds of dead salmon on the shores of the Jim Creek flats on a weekend when that weir was in place.

    I heard a story one time, a few people hooked onto the weir late at night and ripped it out of place and drug it out of the water. After I heard that story I never saw the weir again.

  4. #4
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    Exclamation a little insight

    Weirs are the best way to count fish in Alaska if you can keep the weir in place during high water. The observer can count each fish to species which is something sonar and aerial surveys lack. Sonar tends to count fish targets and then a netting or fishwheel is used to apportion the counts to species. The only exception is the Kenai early and late run chinook sonar which uses a distance criteria to separate species. By the way this is very suspect and probably not defendable in the tidal influenced area they operate.

    Aerial surveys are terrible for getting a good count. First you have to do them multiple times to get a total return estimate. You also need to estimate the average time the fish are alive in the stream. After that you have to correct for those fish you miss by doing some type of ground survey. It is very common to see less than 50 percent of the fish from the air. All this comes together in a model program called area under the curve to get the total return estimate.

    ADF&G does use peak aerial survey counts to get an impression of the run strength but that is very imprecise and only a crude estimate of stock status.

    Relative to behavior of fish behind a weir they will concentrate but the weir itself sometimes is not the reason for fish not moving. I have seen thousands of sockeye salmon behind a weir that is totally open and they will not move during the day. However, at night they pour through the weir. So fish behavior has a lot to do with biological triggers to move rather than the weir itself.

  5. #5

    Default

    Nerka,
    I hear ya, but regarding fish behavior and mortality, I can only speak from a lifetime of experience watching fish in the area on the Deshka River where the weir in question is referenced in this thread. Never before the weir, did Kings spawn below that point, now thousands do. No where else on the entire river will you see the dramatic numbers of dead fish, except within 100 yards of the weir. Carcass' are piled high in the flow directly below the weir. I have watched the weir in process and the fish are continually fighting for position and space at the weir, in other holes, they simply mill around. You are correct in thinking biological triggers want to make them move, but the fact remains the weir interferes greatly with that powerful driving force. Perhaps sockeyes differ greatly to weirs than Kings, don't know. These are Kings and Silvers that I have witnessed dying and struggling in the currents below the weir. There have also been long periods of time, when someone for whatever reason, was not available to release the fish. These times exasperate the problem. Sometimes there are so many fish in the box, the attendant can only make a guess to the actual numbers and then open the box for the release upriver. This system is flawed as well as others. As far as Aerial surveys, my experience tells me I can count every fish in a given hole on the Deshka and other rivers I personally go to. If I were to photo the hole from the air, no King would escape the count. Silvers now that would be impossible, as the numbers are normally to great and they tend to mass up and school more than Kings.

  6. #6
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    Smile fish behavior

    I have not visited the Deshka but if fish are dying in large numbers below the weir because it significantly alters behavior then the weir should be moved.

    If fish are stacked up because personnel are not opening the weir correctly then the people in charge should be held accountable. In that case it is not the weir but the operators. However, if the water temperatures get too high or oxygen too low because fish are stacking up then again the weir location or operation is not being done correctly. If one observes this they should contact ADF&G sport fish regional staff with these observations.

    One comment is that dead fish coming downstream from spawning hang up on weirs. Personnel usually pitch them on the downstream side. Therefore, dead fish will accumulate in this area. I am not sure what type of weir the Deshka has - self cleaning or by manual labor.

  7. #7
    Member slimm's Avatar
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    Default Weir

    i stopped at the weir on the 22nd of june,just to see how it all worked.
    a young fella came down and opened the gates front and back right away fish started blowing through so fast and so many i have no idea how he could have counted so many so fast.
    i asked him how he could tell the difference if two different species moved through at the same time.
    he told me he could tell the silvers by shape and color of tails,plus he said the silvers are constantly losing scales.
    from what i saw while there i am sure it is a very rough count when its all said and done. and most likely off by thousands.
    there were some bows hanging out on the up stream side of the gate a couple of them I'm sure were around 25 inches.
    i dropped some single eggs down in front of them and they viciously snapped them up.
    i did see some dead fish down stream from the weir i asked him whats up with that he told me they are fish drifting down and he would toss them over to keep the weir clean.

  8. #8
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    Default Warm Water

    I am new to the Deshka but I did notice the water wasn't as cold as I thought it would be. I am sure that the warmer temps may stress the fish out as well. Maybe they should have a second gate on the other side of the river so at peak times they could release more fish through? Looking at the charts from previous years you can judge when the peak times are going to be aproximately and have another worker on hand to handle the other gate.
    I just bought a place upriver of the weir and I plan on moving out there next year. If the weir is creating a stress problem then it should be looked into. What good are the fish going through if they are going to be very stressed out before they complete the task or worse yet die before they get there?
    If you take the woods out of the woodsman you have nothing left but a man in the woods.

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