According to police, the fishermen were headed towards Kochi from Gujarat when they suffered from vomiting and loose motions near the Jaigad port in the district.
The fishermen anchored their boat 'E Faim' at the port and sought help of port authorities.
Local police rushed to the aid of the the fishermen and shifted them to Ratnagiri civil hospital, located around 55 kms away from Jaigad town.
The deceased was identified as F. Rajumon (38).
Three other fishermen are undergoing treatment and are said to be out of danger, a police official said.