A joint navy and coastguard operation intercepted the vessel in Indian waters on Monday, apparently headed for the western state of Gujarat, Indian navy spokesman DK Sharma said.
"Using fishing boats to smuggle heroin is a new strategy by Pakistani smugglers," said Sharma, adding that the smugglers were using phones and GPS systems to allow trans-shipment to another boat.
Eight crew members from Pakistan were detained and were in police custody in Gujarat, he said.
The Narcotics Control Bureau, a specialized police force, said the confiscation of heroin on Tuesday was one of India's biggest recorded heroin seizures.