 |
Scientific Name: Thunnus thynnus
Category: Fish
The Atlantic Blue Fin Tuna, one of the largest fish in the world, is torpedo shaped for swift movement through the water. They swim at 7.5 km/hour (4.66 miles/hr), but when they are chasing food, they can reach speeds of 100 km/hr (62.137 miles/hr)! The name tuna comes from the Greek word meaning 'to rush', an appropriate name as communities of tuna called 'schools' swim very, very fast through the ocean. The average length of a tuna is 2 meters (6.5 feet), but they can sometimes reach lengths of 4 meters or more (13.12 feet). This large fish can weigh up to 680.38kg (1500 pounds). The Atlantic Blue Fin Tuna is the largest of all the tunas and belongs to a group of fish called 'boney fish' - meaning they have a skeleton made up of real bone, not cartilage like sharks. They also have fins for swimming and large jaws. This tuna species is found throughout much of the Atlantic Ocean, from Newfoundland, Canada in the northern hemisphere to Brazil in the southern hemisphere.
The tuna are a bright metallic blue on top and white on their sides and belly, reflecting the use of color for camouflage from enemies above and below. The Atlantic Blue Fin Tuna is considered warm blooded, since they use their muscles to generate about 95% of their body heat. This internally generated heat keeps them warmer than the surrounding water and helps them to swim faster. To help them swim even more efficiently they have a crescent-shaped tail and a pointed, rigid head, as well as eyes that are flush with their body. These features reduce the slowing effect of water friction (drag) as they swim. They swim so fast that water does not pass over their gills as with other fish. Instead, they swim with their mouths open and oxygenated water flows in. If they stop swimming, they will die of suffocation!
The Atlantic Blue Fin Tuna returns to the same spawning sites every year. They spawn (lay eggs) in the warm waters of the Gulf of Mexico and the Mediterranean Sea. In the Gulf of Mexico, the Tuna spawn between mid-April and mid-June, while in the Mediterranean Sea the spawning season lasts from June through August. Female tunas are typically around eight years old when they lay their first hatch of eggs. Males and females swim together during spawning, which typically occurs at night when 10+ million eggs are released from each female. This may seem like a lot, but each individual egg has only a 1 in 40 million chance of surviving and maturing into a full grown adult tuna. After spawning, the adults swim back to the Atlantic Ocean.
Following spawning, the eggs float just below the surface where most are eaten by other fish. Just three days after the eggs are fertilized, they hatch. These larvae have very large jaws and heads helping them to feed very early in their lives. They grow very quickly and by three months of age can weigh ½ kg (1.1 pounds). Juvenile Atlantic Blue Fin Tunas remain in the Gulf of Mexico or the Mediterranean Sea for about a year before moving out into the open ocean. Once in the open ocean, juveniles swim in very large groups called 'schools' that help to keep them safe from predators until they reach their full adult size. When full grown, the tunas live for 15-30 years. From tagging and monitoring their migration routes, scientists have observed that adult Atlantic Blue Fin Tunas like to travel and that about 30% of them cross the Atlantic Ocean from west to east, in any given year. Some fish who really love to travel even go both ways in the same year!
The Atlantic Blue Fin Tuna has the best eyes of any fish and they use them to hunt their prey. The tunas gorge themselves on anchovies, herring, mackerel, starfish, squid, eels, crustaceans, and sometimes kelp. They are known for their deep dives in search of food and can go down as far as 1,000 meters. They eat and swim almost all the time, and even can filter feed zooplankton (very small animals) if no other food is available. Since they swim so fast, they need to feed almost continuously. Although they are fast, they themselves still have predators who feed on them, including killer whales, pilot whales, sharks and humans.
The Atlantic Blue Fin Tuna has long been a very tasty fish for humans and it is a popular ingredient in sashimi (a dish of thinly sliced raw fish of Japanese origin). This tuna is low in salt and is a good source of vitamins and minerals. The Atlantic Blue Fin Tuna is also a popular fish with sports fisherman. Fishing tournaments were common in the middle of the 20th century, as the Atlantic Blue Fin Tuna are a challenge to catch! After the 1960's sport and commercial overfishing caused the tuna population to decline. Commercially, the tuna are caught with large nets by huge fishing fleets with onboard freezing facilities. Unfortunately, the large nets used to catch entire schools of tuna, also catch and trap sea turtles and dolphins.
Through international cooperation, The International Commission for the Conservation of Atlantic Tunas (ICCAT) helps to bring awareness of over fishing and the resultant decline in tuna populations to the public. They also help to set fishing limits and regularly monitor the tuna populations. Most recent studies indicate that the tuna population has decreased by 90% since the 1970's and is close to commercial extinction, meaning that fishermen may no longer find them in the ocean.
Research Links Related to Atlantic Bluefin Tuna:
|
 |
