As soon as he saw the hulking, bone-white carcass of an ocean sunfish sloshing in the waves offshore of the Azores archipelago, José Nuno Gomes-Pereira suspected the animal might be a record-breaker.

Subsequent forays along the same coast, between 1515 and 1517, secured more than 30,000 pesos of gold. The precious metal was also found in expeditions in the Bay of San Miguel and to the west on ...