1)There are two species of shrimp native to Indiana. The Ohio shrimp, Macrobranchium ohione and the Mississippi grass shrimp, Palaemonetes kadiakensis.
2) The Mississippi grass shrimp probably needs a fairly deep refuge where water temps remain in the 37-38 degree range. In very shallow ponds, the bottom temps may get lower than this causing high numbers to die. This is partial speculation on my part based on things I have read about this species. I would think to ensure decent survival rates, you'd want a water body with a depth that would also support fish life in the winter.
3) I doubt they would have much affect on other invertebrate populations. Other invertebrates could be crayfish, larval insects, zooplankton, etc... Mississippi grass shrimp feed mostly on dead plant and animal material and graze on small invertebrates that grow on the surface of living plants, submerged dead woody cover and rocks. I don't think they would compete with food sources with your BG or RES but rather be a food source for them along with smaller CC and LMB.
4) The Ohio shrimp actually reaches a fairly large size, plenty big enough to eat at about 4". However, due to water manipulation such as dams and channelization they have become very rare except in the lower Mississippi where their trip back to the ocean is much shorter. They must migrate back to the ocean to spawn and these manipulations have made that migration very difficult.
The Mississippi grass shrimp on the other hand do not require migrations to the ocean to reproduce. They are able to reproduce in freshwater. Females reach a maximum size of about 1.5" and males about 0.75".
I think as the word gets out and the value of grass shrimp as forage, particularly for those trying to grow quality panfish, the stocking of them will be more common. Ideally they should be stocked when you would stock your FHM. But unlike FHM, I believe they can be stocked after a fish population has been established and a reasonable expectation of them taking hold can be expected if the right conditions exist.
