We currently own an 8 acre spring fed pond in Southeast Nebraska. We have encountered an issue with shad and green sunfish. We would like to add white bass, striped bass or hybrids to lower the amount of shad and green sunfish. Our pond consists of freshwater drums, a few carp, crappie, largemouth bass, bluegills, yellow perch and channel catfish. Will the addition of white bass, striped bass or hybrids damage our current population of freshwater drums, a few carp, crappie, largemouth bass, bluegills, yellow perch and channel catfish to an extent where it poses a serious issue. The pond contains mainly fallen trees, drop offs, rocky out crops, and submerged aquatic plants. The pond has a sand, gravel and small rock floor due to the fact it used to be a gravel quarry fifty years ago.
Adding HSB (hybrid striped bass), in my opinion, can do no harm to your established fish populations. Will only add a bonus fish for angling. I don't believe they'll help you too much with your predatory needs, however. For that, need to look at your LMB (largemouth bass) population. How is it? What size of LMB do you usually see? If there is a quality population of good numbers and size of LMB, the GSF (green sunfish) shouldn't be a problem. What kind of shad do you have? Can you post a picture?
Like Omaha was eluding to... It sounds like you may not have many larger LMB, say 18"+ fish. Also, if GSF are causing an issue, you may not really have many LMB or BG period. Generally, when LMB and BG are present, GSF do not compete well. They will usually continue to be present however they simply are forced into heavy rocky/vegetative cover and their numbers drop in comparison to BG numbers.
Larger LMB will help control gizzard shad which is most likely the species you have as threadfin shad most likely will not survive the winters of NE. Pure striped bass would not do well most likely dying within a year or two because of lack of DO and high water temps. White bass do not get a big enough mouth to effectively prey on all but the smallest YOY gizzard shad. The best choice would be the HSB which are a happy medium. They can handle warmer lower DO waters, especially when less than 6 pounds in comparison to pure striped bass. Their mouth size is a bit larger than white bass and because they can grow larger than white bass, they are able to prey on bigger shad. Although HSB readily take pellets, if you don't feed them pellets they can be effective predators on smaller shad and other open water forage fish such as golden shiners.
I would start collecting the relative weights of your LMB. I have a suspicion you may have too many LMB in the 8"-12" range. They are stunting and getting no larger. The gshad are fast growers and very prolific. This means large numbers of gshad are growing fast enough to become too big for the smaller LMB to prey on. They then stock pile at around 12".
Is there any way to drain the pond? You can work on this fish population but you are looking at lots of work and years before you see good results in all likelihood. I may be a good idea to renovate and start fresh depending on some other factors. Would you consider renovation(starting over by killing off all current fish)?
Even LMB can't control GShad in northern waters when they get big and overwinter. You would need 24 in LMB +- to eat 12 in GShad. If it is the GShad you want to reduce then check on seining them in areas where possible. With all those species present the GSF should not be a problem.
I know it sounds like a huge undertaking, doing what CJ suggests and starting over, but it is the best option given your situation. You will find, in the long run, that your pond will be better for it and you will actually save money doing this as well.
Are you sure they are GSF? A 10" GSF is a very larger GSF... Can you take photos and post them?
As ewest said, managing a pond that has gshad is a nightmare if the fish population is out of balance. In more northern waters, nearly impossible. I would strongly consider a complete renovation.
Gshad are more susceptible to retenone than most other species. You may be able to do a low dose treatment once or twice a year and really knock their numbers back without killing off the other fish. Or you can kill off all the fish and start over... The latter would be what I would recommend.
To completely kill the pond, you don't have to drain it completely, even draining 1/2 to 3/4 of the water will concentrate the fish in a smaller area, and that will allow you to use less rotenone to kill them.
I only know of one pond where HSB or wipers have successfully reproduced. They can, but it's extremely rare. I do not think stocking HSB will help you achieve what you are looking for if it is the control of over abundant gshad and GSF.
Contact some of the Neb group here and see if they know any commercial fishermen with gill nets. They can do a number on the GShad. Or you may be able to do an open water partial rotenone to reduce them. Before you decide to just start over you should get a pro to look and make a population analysis.
Depends on what you're looking for exactly. Some fish you can get from your fellow PondBossers. For LMB you can call Rob Hofpar 402.784.6005. But let us know what you're looking for specifically first.