Hi Folks, new member here. I've read lots of great info here!

The subject is a small dugout (probable former agricultural pond) which is on the side of an interstate road. High nutrient, presumably low oxygen. It receives quite a bit of runoff as well. Species are Golden Shiners, Brown Bullhead and a few Bluegill. Dimensions are conservatively 75x20x4. It's quite stagnant and has abundant but not overwhelming algea and milfoil.

A typical generic minnow trap set at the pond for 6 hours will net 40-80 fish. In a typical trap >5% of the shiners are 3" and >1% over 3.5" - most are in the 2.5" range. Bluegill comprise >5% of the total catch and I've never had one bigger than a half dollar. Many of the Bullhad are 7"+ and always plump with shiners.

I'd like to achieve much bigger growth. By commercial bait standards everything is small and medium small. I'd like medium heavy and large.

I have no idea how many fish there are and how many fish to take out or if its even be possible to grow bigger fish in this particular pond.

Any questions please ask. I appreciate everyone's input.

Welcome!
So are you wanting to manage this as a bait supply pond and just want them bigger or are you looking to make a fishing pond out of it??

Thanks for asking Snipe. I'd like manage this as a (personal) bait supply pond. My aim would be to harvest ~400 fish each year that are 5"+. I was recently given owner permission to use the pond which is why I'm now willing to put work in to it.

I'm just not sure if it's a food problem, overcrowding, too little d.o. or all of the above.

Point-blank, the bullhead are a problem just because of the numbers they can produce and how they disturb bottom sediments. The BG with no predation are going to do basically the same as far as numbers being uncontrolled.
I'm going to guess because of competition, the GSH are maxing out in the 3.5" range and then lifespan is up.
removing BH and BG are 2 of the tougher fish to eradicate.
My recommendation would be to tank as many GSH as you can and then nuke the pond and return your gsh stock. The offspring from your returned fish will be able to grow to larger sizes.

Last year I trapped over 1000BH from my main pond the first year it filled. They washed in. I'm at 425 already this year. Hopefully the stocked fish will pack on some weight this year.

Those 7" BH are the best flathead bait you'll find anywhere.

Tha is Snipe, I appreciate the advice! I presumed the shiners were the issue but it's interesting to learn that the catfish and gill are the major issues with overall growth.

I'd guess by 'nuke', you mean chemically treating the pond to get rid of the undesirable fish? I'm not sure I could get the property owner on board with that, but I will do some research and inquire.

In the mean time I'll work on getting as many of the BH out as possible.

Thanks for the advice I will update.

Tell the property owner that you'd nuke the pond with Rotenone, clean out the pond and restock it with golden shiners. Make sure that you will have the use of the pond for at least 4-5+ years.

If I was in your shoes, ideally the pond could be nuked then pumped down with a 3" or 4" semi trash pump. Clean out the pond of any hard "junk" that has accumulated. Sticks, branches, tires, etc., then let it fill back up. Stock with 25#-30# of Golden Shiners. I'd feed them to get them to grow quickly.

Get a seine that is 6' tall, 30' long with a mud line. Get it made from 1/4" Ace or Delta knotless netting. Memphis Net and Twine, Douglas Net, etc.

String the net across about 1/3 the pond. slowly pull to the end. use a scoop net to net out the shiners. If you don't get enough, move the seine to 1/2 the pond and pull it the other way.

You will have to kill a lot of the weeds in the pond to be able to seine it, but I think it'll be worth it.

OR, just kill the weeds in the pond, make some sort of grapple hook out of pieces of rebar welded together and drag the bottom of the pond getting all the junk out of it. Then start seining the pond. Toss out every Bluegill and Bullhead you catch.

If you are using a minnow trap, maybe the larger shiners aren't going into the trap. Shiners prefer to live in the open water in the middle of the pond, not near the bottom or the edges of the pond.