Atlantic Blue Marlin - Life Cycle

Life Cycle

Growth and maturity

Atlantic blue marlin reaches sexual maturity at the age of two to four years. Males reach sexual maturity at a weight of 35–44 kilograms (77–97 lb) and females at 47–61 kilograms (100–130 lb). Marlin breed in late summer and fall. Females may spawn as many as four times in one season. They often release over seven million eggs at once, each approximately 1 millimetre (0.039 in) in diameter. Few reach sexual maturity. The planktonic young drift freely in the ocean's pelagic zone. Larvae inhabit the west central Atlantic off Georgia, North Carolina, Florida, Jamaica, Bahamas, and Puerto Rico and also the southwest Atlantic off Brazil. The larvae may grow as much as 16 millimetres (0.63 in) in a day. On their sides and dorsal surface they are blue-black in color, while ventrally they are white. Both the caudal fin and the caudal peduncle (the narrow part of the fish's body to which the caudal or tail fin is attached) are clear. There are two iridescent blue patches on the head, and some individuals have darker spots on their back. In adolescents, the first dorsal fin is large and concave, gradually reducing in proportion to body size with continued growth. Males may live for 18 years, and females up to 27.

Diet and feeding

The larvae feed upon a variety of zooplankton along with drifting fish eggs and other larvae. They progress to feeding on a wide range of fishes, particularly scombrids such as mackerel and tuna; squid; and also, especially near oceanic islands and coral reefs, on juvenile inshore fish. Studies of stomach contents in both the Atlantic and Pacific have found that smaller schooling scombrids such as frigate mackerel, bullet tuna, and skipjack tuna make up a substantial proportion of their diet. Squid and deep-sea fishes such as pomfret and snake mackerel are also important prey items in certain areas. Blue marlin have been recorded to take prey as large as white marlin, as well as yellowfin and bigeye tuna in the 100 pounds (45 kg) range. Conversely, they are also capable of feeding on small but numerous prey such as filefish and snipefish.

Scientists and fishermen have long debated the extent to which blue marlin and other billfish use their elongated upper jaw in feeding. A 2007 Japanese study of stomach contents of fish captured in a commercial trolling fishery found that 130 undigested prey items obtained from 227 blue marlin had spearing, slashing and other injuries that were judged to have been inflicted by the bill.