Shrimp is an important type of seafood. They are so tasty!
I love shrimp just had some last night actually I love them cooked all ways but made a shrimp scampi.
In the united kingdom they are more commonly called prawns.
We actually have prawns here they are more on the sweeter side to me but they are much bigger in size.
Are they freshwarer prawns? I've read they're some prawn aquaculture farm in the US.
Now that part I'm not sure now that you stated that they be in the local fish market so I would hope they are fresh water prawns and not that injected farm raised food. 
The global total for freshwater prawns raised in farms is around 280,00 tons!
So the chances of it actually being fresh water is low, they actually start off as being from the fresh water and they capture them and bring them back to those farms.
China produced 180,000 out 280,000 pounds of the shrimp.