Not meaning to be anal or anything but whether you have one or a few the word is shrimp,never shrimps.
Actually that's not true.
The word "shrimps" is acceptable (though uncommon) when referring to the taxonomic plural. It's exactly the same as "fishes".
e.g. ftp://ftp.fao.org/docrep/fao/009/ac477e/ac477e00.pdf
However you're right, the OP used it incorrectly...but I don't think English was his first language.