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Sportfish Profiles

Bluefin (Thunnus thynnus)

Bluefin Tuna

Written by: Dr. Larry G. Allen

I have seen a lot of really neat fish in my lifetime, but not many can compare to the magnificent bluefin tuna. I remain truly awed by this powerful, perfectly formed creature with its iridescent flanks. The bluefin is one of the largest, fastest and most wide-ranging of all fishes. They are definitely the largest species of tuna with Atlantic bluefins attaining sizes up to 1500 lb. Here is a brief summary of what we know about bluefin biology, focusing on north Pacific bluefin:

SCIENTIFIC NAME - Thunnus thynnus, family Scombridae (mackerels and tunas)

COMMON NAMES - bluefin, bluefin tuna, northern bluefin, atun azul (Mexico)

DISTRIBUTION - World-wide in subtropical and temperate seas. In California bluefin are found from Santa Barbara south to southern Baja. The southern California bluefin are part of the north Pacific population which range from the Phillipines and Japan across to North America.

SIZE & AGE - Off our coast, to at least 6.5 feet and 1000 pounds. The oldest known bluefin was 9 years old. They are very fast growing fish with average size at age being :

AGE (years)

LENGTH (inches)

WEIGHT (pounds)

1

23

10

2

33

28

3

43

60

4

53

109

5

63

177

DIET - Mainly anchovies, sardines, sauries, hake, squid and pelagic red crabs.

REPRODUCTION - Bluefin mature at about 5-6 years and 63 inches in length. Female bluefin may produce as many as 10 million eggs per year. North Pacific bluefin spawn between the Phillipines, Japan, and Hawaii in April, May and June. Further north spawning may extend into August. Young-of-year bluefin live in the waters off Japan. At the end of their first year many fish begin an easrely, trans-Pacific migration into our waters.

FISHERY - Southern California sport anglers generally land fish that are 2-3 years old and weigh 28 to 60 pounds. Bluefin from the western Pacific arrive off of Baja in April and May and may migrate north into southern California in May and June when sportfishers begin targeting them. By October or November these fish have returned south into Mexican waters to overwinter. These bluefin typically remain off North America until they are 3-6 years old then migrate back to the western Pacific into the spawning grounds.

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