The Vietnam Embassy in Australia reports the sentences ranged from two months for the crew to five and seven months for the ships' masters.

In addition, the men forfeited their fishing vessels, which were destroyed by the Australian Fisheries Management Authority (AFMA).

The AFMA said the plea deal and sentence were fair and send a strong message that illegal fishing will not be tolerated.

"Illegal fishing threatens the economic viability and sustainability of Australia's well managed marine resources," said AFMA official Peter Venslovas.

"The convictions and destruction of the vessels are a good result and will send a very strong message to all those considering illegally fishing in Australian waters."

The men had been caught with six metric tons of sea cucumber in a Coral Sea marine reserve off the north coast in June.