Langoustine Fishing

here is a good explanation from the internet:

In the US, the general term is "shrimp". However, in the UK, the term "prawn" is used more often.

A prawn is sometimes called a prawn and a shrimp is called a prawn and a shrimp. Confused? You should be.

The terms "prawn" and "shrimp" are used interchangeably and it does depend on where you live, as to which term will be used. The terms "prawns" and "shrimps" are used in cookbooks, restaurants and markets, but not necessarily correctly.

Some people say that the difference is just in the size. "Shrimps" are used to describe the smaller variety, whilst prawn is used to name the larger members of both species

Believe it or not, there is actually a difference between prawns and shrimps. The difference lies in their gill structure. Prawns have a branching gill structure, whilst the gill structure of shrimps is lamellar.

There is also a difference in the way that the two brood their eggs. Prawns legs are longer than shrimps and the shrimp's front pair of pincers is larger, whilst the prawns second pair of pincers is bigger.

Prawns are similar to lobster, as they have two pairs of small pincers but due to the fact that they are similar in size to shrimps, they are sometimes confused with them

 

They are both families which come under the order Decapoda.

Not a lot of difference really.