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Gill's, When is too many?

Discussion in 'Pond Management' started by TightLine, Jul 14, 2008.

  1. TightLine

    TightLine Member

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    I posted this in another forum. Totally forgot this one was here!
    Is there an easy way to tell when you actually have too many bluegills, meaning when it's hurting your pond and other fish?
    This year I've noticed that the beds and areas of beds has almost doubled over last year. Three deep for about 60+ yds on a pond which is 150 yds by 12-25 yds in places.
    There are LM, not allot but some and a few which are pretty big and a few channels.
    The gill's don't get very big, at a guess max out about 8" but there are allot of them.
    Is there a formula or just if you see a bunch meaning at times 50-75 in an area of 5'X5'.
    Any help would be appreciated. The pond is for practice fishing, and my kid never kept anything but need to know if it's time to start getting some out.


    Thanks,
     
  2. Your pond is probably overpoulated with them since you said the biggest is 8in. What is the size of most of them.
     

  3. TightLine

    TightLine Member

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    I'm guessing 6" is probably average. I'll take the flyrod out this evening and make some notes.
     
  4. Fishman

    Fishman Catch bait???

    Very good link Pondfin posted there, use it, if you fish start coming up light on the weight end of the stick you may have a problem. The most generic indicator of a healthy sunfish population is if you have fish of various sizes. 8" gills are by no means small, but arn't huge either.

    First off, how old is the pond?
     
  5. TightLine

    TightLine Member

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    Great link Pondfanatic. Thanks. need to get a scale.
    Fishman the pond is about 11 years old I guess you would say community pond as four other neigbors back up to it.
    Some additional info. I've learned we have one of the worst shped ponds you can have long and narrow with the banks V-ing in. I learned this about 4 years ago when we had a massive fish kill. I thought someone had poisned the pond but after looking into it we had about three weeks of super hot dry weather then a cold front came through and I beleive the water turned over too fast for the fish. Lost all crappie some gills allot of LM and even saw a dead Smallie.
    The pond was originally stocked with gills and Amur's, I added some LM and a few channels about 10 years ago.
    Since the kill nothing has been added other than a fountain which I think helps move the water around some.
    My daughter and I went back today for about 1/2 hr caught 40.
    3"=1
    4"=13
    5"=20
    6"=3
    7"=2
    8"=1
    While doing this realized not very scientific as we were both using small flies that the smaller fish would nail as soon as it hit water. so for what it's worth.
    I'll get a scale and check weights on chart and see how they look. They actually look pretty healthy.

    Thanks for the help, any other thoughts please let me know!

    Dan
     
  6. Based on the given information your pond sounds fine to me. I would expect to get a similar mix of gills fishing from my pond this time of year and average RW of 1 or maybe a little higher with some variance in different size classes. Of the three bass I sampled on Friday night (trying out my poles before heading to Rocky Fork) one was 13 1/2" and weighted 1lbs 8oz or 1.15 RW and the other was 15 1/2" and weighted 2lbs 6oz or 1.20 RW and their profile looked more like smallmouth than largemouth. The third one I caught was grossly underweight and appeared to have been injured or swallowed something. I should have cut it open but ended up tossing it over the fence since it was getting dark.

    Over time, it is likely that if no fish are removed, your bass numbers will increase while their average length and RW decrease and the opposite for your bluegill.

    You can get an old set of produce scales fairly reasonable and get them certified for free. Mine haven't been certified for about ten years so my weights are technically unofficial.
     
  7. Relative weight (usually abbreviated Wr) is a very useful index, and that is a very nice page you dug up, PondFin@ic, but you have to be really careful about its interpretation. It varies pretty widely throughout the season (even after a hardy meal) and potentially between the sexes. The index also doesn't necessarily apply to juvenile or stunted fish. Notice the sizes of fish at which the table starts. Unfortunaley, when there is a real bluegill population problem, it can be hard to find any 6" fish.

    In developing the index, standard weight (Ws) was set at the 75th percentile. Thus, a fish with Wr=100 can be expected on average to be heavier than 75% of the fish of that same length.

    Another really useful pond management index is proportional stock density:

    PSD = (no. of fish >= quality length / no. of fish >= stock length) X 100

    For bluegill, stock and quality length are ca. 3" and 6" respectively. Be warned, you shouldn't make too many inferences from so small a sample size (especially given the potential bias of selecting small fish with tiny flies), but your "sample" clocks PSD=15. A range of 20-60 is usually considered to be a "balanced" population for bluegill, so if by some chance your small potentially biased sample is actually representative, you might be heading for a few too many bluegill. You might want to try to catch a more representative sample and calculate PSD again.

    Even better is growth analysis, but that's not so easy to get without some extra equipment.
     
  8. Eugene your formula is interesting. I had to read it about 4 times but it now makes a lot of sense. Outside of seining the entire pond or electrofishing, how would you go about collecting an unbiased representative quantity of fish to collect data from.
     
  9. Fishman

    Fishman Catch bait???

    I'm not sure there is way without doing it by one of those means :D The one pondfin posted was very good for your typical person to use.
     
  10. Even a little stratified controlled angling, deliberately targeting adults as well as juvenile fish, could get a little closer to representative. Pulling a seine at just a few sites around the pond's shore would be good too, and is a great way to entertain kids who happen to like getting wet.
     
  11. Dan, I just noticed you give your location as Powell. I'm in West Worthington to your immediate south. I also work with some student clubs at OSU who used to do contracted pond assessments as fund raisers. Feel free to let me know via PM or e-mail if you wouldn't mind me paying a visit sometime. My home page:
    http://snr.osu.edu/myhome/braig.1
     
  12. I have seined my entire pond. The seine I used was 8'x100' (maybe 10'x100'), had a mudline and about 1" mesh and floats on top. My pond was wider than the seine so I tried to do it in quarters, pulling the seine straight out then wrapping the one end back to shore. I expected a few to slip under the seine in the very center of the pond and a few around the end but after several hours, I had only caught a few fish that included a few bluegill, 1 large catfish, a couple of bass and 1 grass carp, not at all representative of the hundreds of fish I see at feeding time.
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    [​IMG][​IMG]

    I also observed an electrofishing survey demonstration on a 1 acre pond performed by the DNR for a trade school. They caught a couple of catfish, several natural hybrid sunfish and a few skinny bass. This pond was compeletely surrounded with cattails and gin clear. You see more fish just walking around the pond.

    Neither method seemed to give a true representation of the population and fishing is more fun IMO.
     
  13. Keep in mind that a representative sample is some smallish number of fish that is supposed to reflect the parameters of the population at large; a sample is not the entire population. Samples are always associated with some degree of error simply because a sample, even a good one, is not the whole population. All the statistics that can be calculated on a sample to make inferences about a population or assemblage are also associated with error. In addition, fish collection gears are all associated with some bias. Black basses (like largemouth and smallmouth), e.g., ordinarily are notorious for avoiding net and entrapment gears, but crappies tend to trap very well; the former would ordinarily be under-represented in a trapnet catch, and the latter might be over-respresented. That's OK. People who like to think about such stuff simply need to be aware of it and plan their sampling to best suit their needs.

    We're straying a little remote to farm ponds here, but this seems relevant to the chat at hand. I actually team teach a fish sampling workshop at Stone Lab on Gibraltar Island (near Put-in-Bay) with friends from the Ohio EPA and Ohio Division of Wildlife in early October. We run fyke nets, gill nets, trawls, and two types of electrofishing gear on Lake Erie. My target audience is undergraduate college students who might be looking for summer internships with state agencies, and they are given preferential registration, but anybody else is welcome to take any leftover spots not taken by undergraduates. If you have that weekend free, and would like to lay your hands to those gears... I should have fees calculated and more formal word posted soon, perhaps within the week.
     
  14. Fishman

    Fishman Catch bait???

    In regards to the last photo, extremely poor form on the seine mans behalf. Ahh! All I can hear is "KEEP THE LEAD LINE DOWN" echoing over and over in my head when it comes to seining. Lots of variables going into success of pulling a seine obviously, and I've seen hauls from ponds produce next to no fish where you know darn well there are thousands.

    At the farm we mainly uses seines with purses and it dramatically increases the catch rate. At the same time, it's important to mention the seines are usually 6-8ft deep and the ponds are 6ft deep max.

    Cool offer Eugene posted, if anyone has the free time I'de highly recommend trying to get involved.