you need to adjust you bass population before stocking any shad. stocking fish (of any kind) is not the solution to a bass heavy pond. bass will eat up everything you stock in short order. harvest your bass and get them back on track. stock shad after you begin to see improved growth. keep in mind no matter what species of shad you stock they are going to displace some of your bluegill. you will still have bleugill they will be in fewer numbers, you may not notice any difference since it sounds like your bluegill are in low numbers now.

I dont recommend gizzard shad to many people. you need a good population of bass over 16 inches to handle gizzard shad. the average sized gizzard shad in ponds and lakes that I manage is 8 inches long. you need big bass to handle that size forage. once your bass get larger you can consider the gizzard shad. In the right situation the bass in your pond will be freakish in size with gizzard shad as forage. to give you an example, I shocked on of my lakes that contains gizzard shad about a month ago. one fish I remember was 21 3/4 inches in length (should weigh about 6 pounds) and its weight was 7 pounds 10 ounces. its relative weight was around 120 %. that is fairly common in ponds with gizzard shad that I manage. None of ponds that I have with gizzards are under 25 acres in total surface acres. I have only seen one pond with gizzard shad in the 2 acre size range. it had more 5 pound bass than any other 2 acre pond I have seen. I dont know if you can expect those results in any 2 acre pond, I specialize in larger bodies of water these days. maybe someone who has some experience with gizzard shad in small ponds can chime in.

you should also consider threadfin shad, they are going to die in the winter up there but they will do well during the summer, if you have that kind of budget. just stock every spring, fertilize the water and stand back. threadfins will spawn like crazy.