The man is suspected, on probable cause, of aggravated use of a false document.
The Coast Guard boarded the ship on Thursday after suspecting it was sailing under a false flag in Swedish territorial waters.
The captain was arrested on Friday and is suspected of several crimes, including lack of seaworthiness.
The ship is on the EU sanctions list. In recent years the ship, which flies the Comorian flag, has transported oil products between Russia and Brazil, according to the Coast Guard.
Sea Owl has also been banned from use by the Swedish Transport Agency and is not allowed to sail further.
The detention hearing is being held today, Sunday.
