Reproduction
The sexual maturity of Atlantic blue marlins is reached at two to four years of age. The breeding season in the Atlantic Ocean is in part of summer and fall. Females may spawn as many as four times in one season. Atlantic blue marlins have planktonic young, which drift freely in the pelagic zone of the Atlantic ocean. Females may release well over seven million eggs at once, each approximately 1 mm in diameter. The young may grow as much as 16 mm in a day.[10] The larvae are blue-black in color on the sides and dorsal surface and white ventrally. The caudal peduncle and caudal fin are clear. There are two iridescent blue patches on the head, and some individuals have darker spots on their back. In juveniles, the first dorsal fin is large and concave, gradually reducing in proportion to body size with continued growth.[2] Males may live for 18 years, and females as many as 27. Larvae are found in the western central Atlantic off Georgia, North Carolina, Florida, Jamaica, Bahamas, and Arecibo and are also found in the southwest Atlantic off Brazil.[10] Indications show that males reach sexual maturity at a weight of 35 kilograms (77 lb) to 44 kilograms (97 lb) and females at 47 kilograms (100 lb) to 61 kilograms (130 lb).[15]
In 1968, Erdman established the relation of gonad weight to body weight for 14 males and 15 females. The weight of the males ranged from 47 kilograms (100 lb) to 123 kilograms (270 lb) and their testes from 55 grams to 2.4 kilograms (0.12 to 5.30 lb). The weight of the females ranged from 33 kilograms (73 lb) to 292 kilograms (640 lb) and their ovaries from 9.1 grams (0.32 oz) grams to 6.5 kilograms (14 lb). As the percentage of body weight, the weight of testes in males ranged from 0.10 to 2.30%, and the weight of the ovaries in females ranged from 0.03 to 3.60%. He concluded that less than 0.10% for the testes and ovaries corresponds to sexually immature specimens. In males, 0.10% to less than 0.70% corresponds to the developing stage with few to many spermatocytes and little or no sperm. A range of 0.70% to less than 2.30% corresponds to the prespawning stage with many spermatocytes and many sperm. The relative weight of the testes decreases to a range of 0.60% to less than 1.60% at the ripe stage but with little or no spermatocytes and many sperm. A range of 0.10% to less than 0.20% corresponds to the postspawning stage where there are no spermatocytes and many sperm. In females, a range of 0.10% to less than 1.0% corresponds to the developing stage with oocytes and no ova or some developing ones, but no easily discernible eggs. A range of 1.00% to less than 3.60% corresponds to the subripe stage with advanced oocytes and pale-yellow eggs. The weight of the ovaries decreases to less than 1.50% of body weight at the ripe stage, but is still 1.00% or more, with advanced oocytes, transparent eggs, and some postovulatory follicles. There are some atretic bodies, many empty follicles, and degenerating oocytes at the postspawning stage, which has a range of 0.50% to less than 1.00%.[7]