To fish for prawns.

ETYM Old Eng. prane, of unknown origin; cf. Latin perna a sea mussel.
Any of various shrimps of the suborder Natantia (“swimming”), of the crustacean order Decapoda, as contrasted with lobsters and crayfishes, which are able to “walk”. Species called prawns are generally larger than species called shrimps.
1. Any of various edible decapod crustaceans; SYN. shrimp.
2. Shrimp-like decapod crustacean having two pairs of pincers; most are edible.