Six people were prosecuted in the Mandurah Magistrates Court on Tuesday for catching more than 200 undersized crabs.
Yi Chen, XueGuang Ge and Yunbin Lin were scooping for crabs at Boggy Bay in January when they were spotted by Fisheries officers.
The court heard when the trio realised they were being watched, they threw buckets containing the crabs into the bush.
Officers retrieved 155 blue swimmer crabs, with 152 of those undersized.
They were all dead.
Chen and Lin were fined $500, while Ge was fined $1200 for giving officers a false name.
All three men were ordered to pay a mandatory penalty of $1467.90.
Three other men were also handed fines for taking 60 undersized crabs from Herron in January.
Xiangliang Song, Xiyou Wang and Yajuan Wang were driving from Island Point when officers saw them turn around before the Fisheries checkpoint.
They were found with 68 blue swimmer crabs, 60 of those undersized.
Song and Xiyou Wang were fined $1000 while Yajuan Wang was fined $500.
They were each ordered to pay a $3150 mandatory penalty for obstructing a Fisheries officer and possessing a protected fish.
Fishers are reminded that the legal minimum size limit for a blue swimmer crab is 127mm which is measured across the widest part of the shell.