Ryan,
My 2 cents worth....draining your pond and starting over is a drastic measure, one taken only when all other options are exhausted. Like most pond issues/questions, there are at least two ways of looking at any problem...and usually more. Which is the right way?
I'd encourage you to read the May/June 04 Pond Boss article for another view. The article, written by Kedric Nutt and based on research by Dr. DeVries, provides a less ominous view of gizzard shad. In addition, note Todd Overton's comments on the referenced thread about his experience with gizzard shad. He recommended gizzard shad to me...but as I mentioned they did not survive.
With that as background and your own anecdotal evidence regarding take-overs by gizzards, my advice is don't panic too soon. Draining the pond and starting over is an option that will always be available.
First, certainly before draining, a predator heavy approach should be tried. Augmenting the LMB with HSB to remove the smaller shad and prevent them from getting to the large size is one option to try. You could easily add 20 HSB to your 1/2 acre, let them work and then remove some in a year or so depending on how things look. In fact, a put and take fishery with HSB where you add a few every year and remove a few for eating, is not a bad way to go. If you can't find HSB in a larger size (8 to 9 inches), then stock the smaller ones expecting a 50% mortality to predation. If mortality is higher than that, then simply stock more of them. The cost of a few HSB is very small compared to draining and starting over and the time lost with that approach. In fact, it may well be cheaper to buy more of the smaller HSB fish than paying a premium for large HSB.
In my view, the HSB will do a couple of things: 1) they will consume large amounts of any small gizzards and 2) they will also consume other small forage e.g. BG and Tilapia and help the LMB concentrate on larger gizzard shad. As a bonus, they will give you great fishing action. You don't have the summer high temps for long periods of time like we have in Texas and hence that problem isn't much of an issue for you.
What's the worst that can happen with this option? If it does not work, you can still drain the pond and start over....and have a huge fish fry of HSB and fat LMB.
Using a cast net may help some briefly, but I doubt it, because over time the gizzards will get very difficult to catch that way. The small gizzards need to be eliminated...HSB can help do that...and the large gizzards need to be reduced...LMB can do that. To optimize the HSB effectiveness, I think I would also limit artificial feeding....encourage the HSB to eat shad, not pellets.
Obviously, Ryan, I'm not in Ohio and do not have Ohio pond experience. I'm offering my thoughts based on my own experiences and in hopes it can help you in some way. Good luck.
