Tunas are one of the most consumed fish species. There are 8 species of tuna. All species of tuna are nomadic, which means that they do not spend their entire life on a single place. Instead, they often change their location. Tunas are usually located in temperate and subtropical waters of Atlantic Ocean, Mediterranean and Black seas. Tunas are over-fished in different parts of the world, especially in Japan and Australia. As a result, number of tunas decreased for over 90% percent since the beginning of 20th century. Although tunas are listed as endangered species, fishermen around the world hunt them persistently.
Interesting Tuna Facts:
Tuna is a large fish. It can reach length of 6.5 feet and weight of up to 550 pounds.
Largest (ever recorded) specimen of tuna was 21 feet long, weighing 1600 pounds.
Color of the body provides excellent camouflage in the water. Dorsal (back) side of tuna's body is dark blue and it blends with the ocean floor when observed from the air. Belly of tuna is silver-white and it blends with the surface of the ocean when observed from below.
Despite their large size, tunas are very fast swimmers. They can reach the speed between 44 and 62 miles per hour.
Tuna is able to change the position of its dorsal and pectoral fins to reduce drag and accelerate the swimming speed.
Tuna can swim near the surface or can dive to the depth of 3000 feet while it searches for food.
Tuna is a carnivore. It feeds on different types of fish (mackerel, herring, hake…), squids and crustaceans.
Unlike other fish, tuna is able to increase and maintain the body temperature few degrees above the temperature of surrounding water. Because of this feature, tuna can be classified as "warm-blooded" animal.
Tuna has unique network of small arteries and veins near the muscles called "rete mirabile" which facilitates warming of the blood. Warmed blood is essential for fast and strong swimming.
Tuna breathes oxygen from the water and because of that it needs to swim constantly.
Tunas can travel large distances in a short period of time. It can pass across entire Atlantic in 30 days by traveling 16 miles per hours
Besides humans, natural predators of tunas are orcas and sharks.
Mating season of tunas depends on their geographic location. Tunas in Gulf of Mexico mate from middle of April to middle of June. In Adriatic and Mediterranean Sea, mating takes place from June to August.
During the spawning, one female can release 30 million eggs. Only 2 of those 30 millions will survive until the adulthood. Remaining eggs will be eaten by other marine creatures.
Average life span of tuna is between 15 and 30 years in the wild. Small percent of tuna managed to survive until this period.