This is the biggest arrest ever by Somaliland's coastguards, trained by Western states to curb piracy and illegal fishing off its coast.
Illegal fishing has depleted fishing stocks along the Somali coast.
Correspondents say years of illegal fishing by foreign trawlers devastated the livelihoods of many people, some of whom then became pirates who attacked vessels for ransom.
Piracy in the region has declined in recent years following the deployment of a multi-national naval force.
Last month, the EU Naval Force provided training and equipment to the Somaliland coastguard.
Somaliland unilaterally declared independence from Somalia in 1991, but is not recognised by the United Nations or any government.