Are you in Belmont County in Ohio?
Even if in another state, look up the "pond recommendations" put out by one of your state agencies. They should have some good info for the depth recommendations. Here is a very basic one for Ohio.
Pond Management - Ohio(They recommend 10-12' as the minimum depth for an area of 25% of the pond.)
Almost every pond construction thread on Pond Boss, includes the phrase "deeper is better". However, due to the geography of your site, every foot of additional dam height and levee height is going to add substantially to your construction costs!
Perhaps if you are digging in good clay, you might excavate deeper in a small area (10% of surface) to create a deep pool in the pond basin - even if you can't quite reach the state recommendation due to budget or location constraints.
I am NOT a fish expert, so hopefully if I make an incorrect statement below, then some expert will drop in to correct it.Your fish listed above could probably survive their whole lives in fairly shallow water under normal conditions. However, I believe there are four main considerations to determine your minimum required pond depth for them to thrive year round.
1.) Drought. The pond must have enough depth for the fish to survive at the lowest water level experienced during the drought period.
2.) Ice over. In cold region lakes, the fish must have enough water under maximum ice thickness to survive.
3.) Plant growth. You need some plants to have a healthy pond. However, a shallow, weed-choked pond effects the ecology of the fishery, and the ability to enjoy the pond for fishing, swimming, etc. Generally, the pond sides need to slope down to "deep" water as quickly as feasible, to reduce the available sunlight for plants that start at the bottom.
4.) Future loss of depth. Essentially all ponds get shallower over time. Your pond construction depth must factor in some allowance for this phenomenon. The two biggest culprits are sediment washing in due to precipitation events, and leaves and other organic matter washing/blowing in and creating a muck buildup on the bottom.
(If your pond is mainly fed through clean, spring water and very few leaves will enter your pond, then this problem should be reduced for your site. However, you will almost certainly lose a little depth when a storm hits your churned up construction site before you have your soil re-stabilized with good groundcover plants.)
I speculate that if your spring does not dry up due to drought, your fish would PROBABLY do fine in a pond as shallow as 8 feet. I think the bigger risk would be overwhelming plant growth. Can you talk to any neighbors, or go boat or fish a little state recreation pond in the area? If the plants are heavy down to 9', then you are going to have to spend the dollars to create a 12' minimum.
I would note that there have been many posts on the forum from people wishing they had constructed their pond a few feet deeper. I have seen very few posts complaining about constructing a pond too deep. (And I think those were for ultra-deep ponds.)
Now that I have typed this long post, I think my best recommendation would be to start a new thread in "Questions and Observations", titled - Minimum Pond Depth in Ohio. We have lots of experts in the forum that manage ponds in Ohio. They should be able to give you some very good, specific advice. Further, I think knowing the "depth" number for your pond is your most important design factor at this point.
