Is there a lake in your neighborhood where you and your dad could catch a couple 10"-12" walleye each trip and transport them back to the pond? One or two fish could be fairly easy to hold an hour or two and when the third fish is caught then transport all 3 home in a garbage can? Holding more than two fish for a couple hours in warmer water could get tricky. Several trips could get you a dozen larger fish to junp start your population.

You will have to be diligent with weed control with a nursery pond just 4'to 6' deep. I am not sure how a fertilization program would work for you based on your water chem. What are the alkalinities in your gravel pit?

aka Pond Doctor & Dr. Perca Read Pond Boss Magazine -
America's Journal of Pond Management