"They hit me, tied me up and 1,000 other things," he said, according to the Spanish newspaper El Mundo.
'Volleys of bullets'
Wilson Pillate, another crew member said the pirates had an array of different guns, including pistols and Kalashnikovs.
"There were times when they would turn wild, firing volleys of bullets in the air," the Reuters news agency quoted him as saying.
"One day in particular they rounded all of us up. They said our days had ended and they would kill all of us."
The Alakrana tuna fishing trawler was captured last month about 740km northwest of the Seychelles island of Mahe, along with its crew of 36 people.
The ship's crew also included eight Indonesians and others from the Ivory Coast, Ghana, Madagascar, Seychelles and Senegal.
The pirates released the ship on Tuesday, saying they were paid $4m for the crew's release, which would be one of the highest ransoms paid.
But the Spanish government has not confirmed it paid any money.
Jose Luis Rodriguez Zapatero, Spain's prime minister, has refused to confirm whether a ransom had been paid, saying "the government has done what it had to do".
Attacks off Seychelles have surged after pirates extended their range to evade navies patrolling off the Horn of Africa.