A rare, 350-pound grouper was captured off the coast of Florida, where a fisherman caught the giant beast with just a hook and line.

Game officials believe the fish was 50 years old, making it the oldest-known specimen to be caught in the state.

The massive Warsaw grouper was caught on 29 December, and biologists with the Florida Fish and Wildlife Conservation Commission's Fish and Wildlife Research Institute age-tested the grouper's otolith, the calcium carbonate bone structure that is used by scientists to help determine the age and environmental conditions of a fish.

Adult Warsaw groupers are a mottled-brown colour with 10 dorsal spines. They're a solitary species, typically living within depths of 200 to 1,700 feet — the 50-year-old grouper was caught in waters roughly 600 feet, according to the institute. Younger groupers are occasionally spotted in shallow water reefs and in jetties throughout the southern Gulf of Mexico.

A 436-pound Warsaw grouper that was caught in Destin continues to hold the state's size record.

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The capture and killing of the rare, old and massive fish has revived petitions to protect the species from capture and to call on federal agencies to list the fish among endangered animals.

Warsaw groupers' population in the Gulf of Mexico is unknown. The Florida Fish and Wildlife Conservation Commission does not encourage the fishing of the species.