Science Name: | Thunnus thynnus |
Other Names: | mackerWestern Atlantic bluefin, Nortel |
Ideal Temp: | 55 to 75 |
World Record: | 1496 lbs. Nova Scotia |
Environment: | offshore |
Techniques: | Heavy-tackle trolling |
Description
Similar to other members of the mackerel family, bluefin tuna has a graceful, streamline appearance. The snout is pointed and the tail region is slender, both leading up to a robust body, hence providing for the "football" name often given to juvenile bluefin. All fins appear streamlined and the dorsal, pelvic and pectoral fins fit into slots in the body to reduce drag. A series of small, yellowish finlets occur from the second dorsal and anal fin to the caudal fin. Bluefin tuna are darkly colored on their dorsal surface with dark, shiny blue tones that can approach black. The dark coloration fades and becomes silvery towards the lateral line. Below the lateral line and the belly are silvery and may have irregular bands and spots that are iridescent white, gray and silver. Dorsal fins are dusky to black and ventral fins are dusky with lighter shades of white, gray, and silver.
Because of their large size, it is usually not a problem distinguishing bluefin tuna from other tuna species. Other than large size, bluefin can be separated from other Thunnus species by their higher gill raker count (34-43), shorter pectoral fin, and presence of striations on their liver.
Bluefin tuna are a fast-growing species that can exceed 10 ft in length and weigh over 1,000 pounds. The largest bluefin tuna caught by an angler in Massachusetts waters weighed 1,228 pounds in 1984, and the all-tackle record for the Atlantic is 1,496 lbs. caught in Nova Scotia in 1979. One-year-old bluefin tuna are about 10 pounds by mid-summer and are a sporadic visitor to our shores south of Cape Cod. Ages 2-4 are typically 20-80 pounds and an annual visitor to feeding grounds south of Cape Cod. There is substantial variation to individual growth once bluefin reach five or six years. Giant tuna is a subjective term used for mature bluefin seen in the Gulf of Maine that typically are at least 10 years old and about 300 pounds or higher.
The bluefin's large size and capacity to visit all the temperate oceans of the world have made it a difficult species to study. There is much we still don't know about bluefin tuna.
Physically, they have the ability to retain metabolic heat, rendering them the closest thing to a warm-blooded fish. Being warmer than the surrounding water allows them conduct physiological processes faster than cold-blooded fish. Food digestion and oxygen transport can occur quicker and more efficiently. And the warmer bluefin can colonize colder regions of the Atlantic in search of prey.
The movements and spawning habits of bluefin tuna still contain some mystery. Spawning is known to occur in the western Atlantic primarily in the Gulf of Mexico and within the Mediterranean Sea over in the eastern Atlantic. We have long known that many bluefin that spawn in the spring in the Gulf of Mexico will head north to feeding grounds along the U.S. continental shelf. There is a growing body of evidence that indicates western Atlantic bluefin tuna can interact with the spawning and feeding grounds in the eastern Atlantic and Mediterranean Sea. Despite being the same species, the expected age of first spawning is quite different for the two groups of tuna. Western bluefin are thought to mature at about age-8 when they weigh near 250 pounds. Eastern bluefin mature at about age-4 when they weigh less than 80 lbs. Hopefully, ongoing research on reproduction, migrations and stock identification will shed more light on the Atlantic stock composition of bluefin tuna.
More than any other fish, the lines between commercial and recreational fishing are blurred when it comes to bluefin tuna. Most giant tuna are sold because of their high value. Yet, many otherwise sportfishermen participate in the commercial end of the fishery, and the saltiest commercial fisherman continues to be thrilled with each hook-up.
Catching giants by rod and reel requires the largest of high quality reels spooled often with 200 lbs. test line. The two primary methods are trolling with rigged natural baits or artificial squids on spreader bars and bait fishing on anchor with live baits or chunks of local prey such as herring or mackerel. The movements of bluefin are highly variable and there are numerous ways to lose a hooked giant. Therefore, catch rates are typically low in this fishery. This fact does not diminish the enthusiasm shown among anglers. The expenditures by thousands of hopeful anglers pursuing bluefin tuna in Massachusetts is an economic force in itself.
Smaller bluefin tuna are fished in similar patterns as the giants, with a downsizing of rod and reel size and line strength to match the target. Anglers south of Cape Cod will often increase the troll speed and use a variety of brightly colored, single hook lures to attract school tuna that can be found among tropical tunas and marlins that can also visit the continental shelf off Martha's Vineyard during the summer.
Take care to bleed and chill your catch quickly. The giants require specific attention to meet their potential value in the Japanese sashimi market. Lift the pectoral fins on both sides and make a one inch incision to cut the cutaneous veins and arteries the run along the lateral line. Tuna should be carefully gutted also soon after capture. The bright red flesh is excellent on the grill after marinating in your favorite concoction. Be sure not to over cook and dry out the flesh. Bluefin is even better eaten raw using wasabi and soy to garnish and spice the ancient ritual.
Tips for Fishing