Adult blue marlin have few predators apart from killer whales, sharks (Shortfin Mako and Great Whites), and humans. They are sought after as a highly prized game fish by anglers and are taken by commercial fishermen, both as a directed catch and as bycatch in major industrial tuna fisheries. Blue marlin are currently considered a threatened species by the IUCN due to overfishing, particularly in the international waters off the coast of Portugal where they migrate to breed in the June/July months.