More About Blue Fin Tuna

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 off the coast of Massachusetts. 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. Until recently, these school tuna were not considered common visitors to the Gulf of Maine, although they were found in high abundance in the Gulf of Maine during the 1940s and 1950s and observations have increased since the 1990s. 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.

Habits
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.

Their ability to stay warm in cool water brings them to the Gulf of Maine each year on a feeding migration. They typically arrive in June and depart in October. They will aggregate and forage on concentrations of small pelagic prey like mackerel, sand lance, sea herring, menhaden and squid. In the absence of large schools of pelagic prey, they will feed on whatever they encounter throughout the water column. Bluefin are a schooling species that usually remain in schools of similar sized cohorts. Jeffreys Ledge, Stellwagen Bank, Cape Cod Bay and the Great South Channel are traditional fishing grounds for giant bluefin. However, movements in the Gulf of Maine and south of Cape Cod are highly variable within each season and year-to-year and certainly depend on forage concentrations.

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.

Management
The harvest and management of bluefin tuna in the western Atlantic has occurred for less than 100 years, unlike the rich history found in the eastern Atlantic and Mediterranean Sea. Bluefin tuna were not an important target species on the East Coast of the United States during the first half of the 20th century. Most commercial landings came from handgear catches in Maine and trap net catches in Massachusetts. The latter half of the 20th century saw major technical changes to bluefin tuna fisheries that resulted in stock reductions and prompted extensive management measures. Three major developments have had the greatest impact on bluefin tuna in the Atlantic: development of purse seine fishing in the late 1950s, development of high-seas longlining by the Japanese in the late 1950s, and the opening of the high-price Japanese sashimi market in the 1970s.

Concerns over the health of Atlantic bluefin populations in the 1960s and 1970s resulted in domestic and international management efforts. The commonwealth of Massachusetts enacted the first bluefin tuna regulations in the United States in 1974 in order to protect bluefin tuna in Cape Cod Bay. In 1975, the International Commission for the Conservation of Atlantic Tunas (ICCAT) enacted its first restrictions on Atlantic Tuna and the U.S. Congress passed the Atlantic Tuna Convention Act to authorize the Department of Commerce (through the National Marine Fisheries Service) to implement ICCAT regulations. In 1982, ICCAT separated Atlantic bluefin tuna into western and eastern Atlantic management stocks based on the assumption of separate spawning grounds and negligible movements between stocks. This management regime is still in place and outstanding questions over stock identification and allocation have been controversial for 20 years. Numerous countries now share an eastern Atlantic quota that is comparable to historical high landings. The U.S., Canada, and Japan share a quota for the western Atlantic that is modest relative to historical high landings. There is growing evidence from high-technology tagging and stock identification methods that suggests there is substantial interaction between the stocks. This information, along with allocation disagreements, and increasing fishing pressure on the high seas by longliners fishing in violation of ICCAT rules have created a very difficult management scenario.

Recreational Fishery Regulations
Both the recreational and commercial fisheries for bluefin tuna are regulated by the National Marine Fisheries Service (NMFS). Click here for more information, or call 1-888-USA-TUNA.

Angling and Handling Tips
Bluefin tuna are one of the greatest challenges to anglers off the coast of New England, and Massachusetts continues to be a center of activity for giant bluefin tuna. Massachusetts has been the top state for commercial landings nearly every year since the late 1940s. The port of Gloucester has been the top handgear port for bluefin tuna on the East Coast during most of the last 50 years and recently Harwich has taken the lead on the graces of high catch rates in the Great South Channel.

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 sport fishermen 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.

Description & Behavior
Atlantic bluefin tuna, Thunnus thynnus (Linnaeus, 1758), aka bluefin tuna, horse mackerel, northern bluefin tuna is regarded as one of the most highly evolved fish species and one of the most prized fish in danger of over fishing. Tuna, originating from the Greek word meaning "to rush," usually swim at speeds of 1.5-4 kts, can maintain 8 kts for some time, and can rarely break 20 kts for short periods. These are some of the most magnificent creatures in the sea. One fish can sell for tens of thousands of dollars. The highest amount paid for a bluefin was $180,000 on the Japanese fish market.
The Atlantic bluefin tuna is the largest member of the Scombridae Family (albacores, bonitos, mackerels, tunas). It is one of the largest bony fishes and can reach lengths of up to 3 m, although they are more commonly found from .5-2 m in length. Adult weights range from 136-680 kg, although the upper weight range is rare. They can dive as deep as 914 m, and are known to swim long distances as they are a highly migratory species.

Atlantic bluefins are dark blue to black near the dorsal surface and silvery near the ventral surface. The bluefin is known for the finlets that run down the dorsal and ventrals sides toward the anal fin. There are 12-14 spines in the first dorsal fin and 13-15 rays in the second dorsal fin. The anal fin has 11-15 rays. The average lifespan of bluefin tuna is 15-30 years.
Atlantic bluefin are homeothermic ("warm-blooded") and are therefore able to thermoregulate keeping their body temperatures higher than the surrounding water, which is why they are so well adapted to colder waters.

World Range & Habitat
Atlantic bluefin live in subtropical and temperate waters of the North Atlantic Ocean, the Mediterranean, and Black Seas. Bluefin are highly migratory and limited numbers of individuals may cross the Atlantic in as little as 60 days and are widely distributed throughout the Atlantic and can be found from Newfoundland all the way to the coast of Brazil. They range in the eastern Atlantic as far north as Norway and down to northern West Africa. Bluefin tagged in the Bahamas have been captured in Norway as well as off the coast of Brazil. Bluefin in the South Atlantic belong to a distinct southern population, with known spawning areas south of Java, Indonesia. The bluefin is pelagic, schooling fish. They tend to group together according to size.

Feeding Behavior (Ecology)
Atlantic bluefin tuna consume smaller fishes such as mackerel, herring, whiting, flying fish and mullet as well as squid, eels and crustaceans.

Life History
Although Atlantic bluefin are widely distributed and migrate thousands of kilometers, there are two confirmed spawning locations—the Gulf of Mexico in the western Atlantic and the Mediterranean Sea in the eastern Atlantic. Although many ecological and environmental variables undoubtedly affect both the location and productivity of spawning in these two areas, relatively little is known concerning why bluefin spawn where they do.

Spawning in the Gulf of Mexico occurs between mid-April and mid-June when females, which mature around age 8, release approximately 30 million eggs each. The highest density of bluefin larvae, the primary indicator of spawning, occurs in the northern Gulf of Mexico with lesser larval concentrations appearing off the Texas coast and in the Straits of Florida.

In the eastern Atlantic, spawning occurs exclusively in the Mediterranean and Adriatic Seas from June through August, with the highest larvae concentrations appearing around southern Italy. Although some fishery biologists believe that eastern Atlantic bluefin reach sexual maturity several years earlier than western Atlantic bluefin (possibly as young as ages 4-5), this understanding has been criticized.

Comments
International sport fishing for giant bluefin originated about 100 years ago, becoming popular domestically in the early 1900s. The Sharp Cup in Nova Scotia was a distinguished international bluefin tournament held from the early 1930s through the 1960s, with a peak landing of 1,760 fish in 1949. Many other tournaments existed throughout the NE United States until the mid-1960s, when giant bluefin abundance near tournament sites appeared to decline. Although studies have been inconclusive regarding these changes, suspected causes include changes in water temperature, oceanic currents, availability of food, and a declining population of giant western Atlantic bluefin.

Prior to 1970, sport fishing was exclusively recreational, as giant bluefin tuna had a commercial value of only $.05 per pound. Giant trophy tuna that were not kept for personal display or consumption were sold to cat and dog food producers. With the development of the Japanese specialty market in the early 1970s, giant bluefin tuna suddenly represented big money to traditional sport fishermen. Perspectives on the fishery shifted, and the recreational character of the fishery was altered by economic opportunity. A giant 225 kg trophy fish was, by the late 1970s, a highly valued Japanese delicacy. Participation exploded and the giant bluefin fishery capitalized quickly.

Now many "recreational anglers" also obtain commercial permits, so that virtually all giant bluefin tuna currently caught are marketed commercially, except for a small scale catch-and-release sport fishery in the Bahamas. A substantial charter- or party-boat fishery for small Bluefin tuna also exists from North Carolina to Massachusetts. Estimated at more than 15,000 recreational anglers annually, this is the only U.S. fishery allowed to catch bluefin smaller than the minimum commercial size (1.78 m from the tip of a fish's snout to the fork of its tail).

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