Although there is still much to learn about fish migration patterns, as well as where and when certain fish species reproduce, the Bluefin tuna is one of the most studied. Over 40 years of research on the Bluefin has produced a wealth of information and makes the Bluefin a classic example of how far and wide a fish species can roam as it runs the gauntlet of commercial and factory fishing vessels that ply the Atlantic, Indian, Mediterranean, and Pacific Oceans.
One of the more desirous fish in the sea, the Bluefin tuna is highly prized in sushi and sashimi served to Japanese diners who are willing to pay exorbitant prices. In 2001, a Bluefin weighing 444 pounds was sold at a Japanese auction for US$175,000 while the average price for a Bluefin of lesser size is around US$45,000.
Atlantic Bluefins average six to seven feet in length with the largest recorded at 15 feet, weighing 1,550 pounds. They can swim 45 miles per hour, a speed facilitated by their bullet shaped bodies, and they can dive more than 3,200 feet. Very beautiful fish, Bluefins have a well defined lateral line below which their bodies are silvery white while the upper body is a metallic midnight blue capped by two dorsal fins. Bluefins have the ability to thermo-regulate which allows them to live in cold and tropical water.
They range from Labrador through the Caribbean into northern Brazil and from Norway to the Canary Islands. Some of the Atlantic Bluefins have been tracked crossing the Atlantic from its western to its eastern shores and back again in a single year. There is a report of a 35 pound Bluefin tagged in the Pacific off Mexico in 1958 that was caught five years later, 6,000 miles away off the coast of Japan, having increased in weight by 200 pounds. Another tagged Bluefin traveled almost 1700 miles during the 90 days it was tracked.
There are two general populations of Bluefin tuna in the Atlantic; the Eastern Atlantic where Bluefins tend to be smaller (perhaps not genetic but rather from taking at younger ages) and the Western Atlantic population with the larger and sometimes record setting “giant” Bluefins. Although they are considered separate populations, there is increasing evidence that the two groups intermingle during their far-ranging migrations with some crossing the Atlantic in as little as two months.
Reaching sexual maturity around 8 years of age, a female Bluefin can produce between 10,000,000 to 30,000,000 eggs per year. In the Western Atlantic the free floating eggs and larvae are carried by currents out of the Gulf of Mexico where they are picked up by the Gulf Stream and carried throughout the Atlantic on circular currents.
If they are fortunate enough to avoid commercial fishermen, Bluefins can live up to 30 years. An adult female that lives for 30 years has the potential of producing over 200,000,000 eggs in her lifetime. While only a small percentage of those eggs survive to adulthood, a single female’s ability to continue the species is critical.
Prior to the early 1970s Bluefin tuna meat was sold for around five cents per pound. With the increase in popularity of sushi and sashimi, particularly in Japan, the price soared and Bluefins have been hunted to the brink of extinction. Both the Western and Eastern Bluefins are red-listed by IUCN (the International Union for the Conservation of Nature and Natural Resources or World Conservation Union.) Current estimates put their populations at a mere 10% of pre-1970 numbers—a loss of 90% in less than 40 years.
During migratory journeys through the world’s oceans they face not only natural predators such as sharks and toothed whales but, even more of a threat to their existence, commercial fishing vessels: trawlers towing nets miles long that take every living thing in their paths, longliners with hundreds and hundreds of baited hooks, gillnets, drift nets, purse-seines, and traps.
What countries take the Atlantic Bluefin? Japan and Norway top the list with catches as large as 14,000 tons each in one year. Spain, France, and Italy are not far behind, followed by Turkey, Morocco, the United States, Libya, and Tunisia. Some use factory ships, several football fields long, with helicopters on board for spotting Bluefin schools.
A Bluefin caught off Norway ends its journey there. Another caught off Spain swims no further. A third caught by Japan in Brazilian waters ceases to exist, quite possibly taking with it tens of millions of eggs that could have perpetuated the species.
Bluefin do not belong to one country…they move with the currents, they are driven by ancient forces to spawning grounds thousands of miles away. The death of one Bluefin in the Bay of Biscay may seem to have little consequence in the Caribbean until we realize the loss of one fish represents the loss of so many that their numbers are incomprehensible.
Sustainability in Commercial Fishing Series
Becky Bauer takes an in depth look at today’s Commercial Fishing…
After many years of debate, the dogged determination of environmental groups, and scientific studies, the cause of many large-scale disasters—killing floods and landslides, starvation from lack of topsoil in which to grow food, air and water degradation—is now recognized as a threat to global security. This threat is the clear cutting of forests throughout the world.
I am certain you are wondering what clear cutting has to do with commercial fishing. A recent study conducted by Dr. Les Watling of the Darling Marine Center at the University of Maine states that commercial bottom trawling and dredging destroys 150 times more sea bottom than clear cutting destroys forests per year. 150 x 16m = 2400m acres of sea bottom per year; 2,400,000,000 acres, a number so large as to be almost incomprehensible.
Take a walk with us and begin to understand the repercussions of our actions… AWARENESS and Understanding are the keys to sustainability.
- It WILL Affect You – The Tragedy of Commercial Fishing
- One Fish Lost
- What is Commercial Fishing
- One Hundred and Ninety BILLION Pounds of Fish
- 10 Billion Hooks are a Small Part
- Wall of Death – Gillnet Fishing
- Purse Seining – A Terrible Beauty
- For Every Action – A Reaction
- Back to the Drawing Board – A Good Plan Gone Wrong