Tuna fish, is also known by its scientific name of Thunnus. About 12 species that inhabit in the Ocean; comprise this genera.
These fish are located in a higher position in the food chain, mainly because of their large size.
These fish also have excellent swimming skills, being one of the most consumed species in the world’s gastronomy. In spite of having many properties, which bring many benefits for humans health; their disproportionate fishing could mean their extinction as species.
Table Of Content
Main Characteristics Of The Tuna Fish
The Blue fin tunas are characterized, by their skill to swim at high speeds of up to 110 km/hour in some cases. This speed is developed in short distances; and their average speed ranges between 3 kilometers per hour, and 7 kilometers per hour.
These fish are also known, for carrying out long migration journeys, for reproductive purposes. In the case of long-distance trips, tunas fish run roughly 14 kilometers and up to 50 kilometers per day. This type of route usually lasts about 60 days depending on each species.
On the other hand, it is known that they can reach 400 meters of depth; when they swim. The tunas usually swim in groups ( shoal), of several individuals of the same species.
It is confirmed that these animals can adapt to the temperatures provided by the environment. In this sense, we can mention the case of the blue fin tuna fish (the biggest specie of tuna fish ); which can withstand and survive the changes of the environment, in a better way than others species. The ability of this fish, to increase its internal body temperature, when the water temperatures become colder; is the main reason of its adaptability.
These animals don´t sleep nor rest, unlike other marine species; so they are known for staying in constant movement. This fact leads them to oxygenate constantly. . In the same way, the tuna fish swims with its mouth open, in order to send water to its gills where they extract the oxygen they need. This is the way how their breathing system works.
According to several studies, these fish live for approximately 15 years
Anatomy Of The Tuna Fish
In general terms to talk about the anatomy of the tuna fish, we must take into account that its body has a fusiform aspect and is usually consistent. Its texture keeps it firm and strong. In turn, these fish have two dorsal fins, which are very separate. In the case of the first fin , it is supported by spines, and the second one by soft strips.
On the other hand, its body is oval and completely covered by small scales. Its back has tonalities in dark blue, and its belly is light silvery in color. In the same way, its fins have different tones of gray. The tunas fish lack of spots; which is another distinctive feature that gives them the ability to camouflage with the aquatic environment, since their tonalities resemble the colors of the depths of the ocean.
Regarding their size, it ranges from 3 up to 5 meters depending on the species; and their weigh reaches 400 kilograms, even 900 kilograms in some cases.
Reproduction Of The Tuna Fish
It is known that these fish reach sexual maturity when they are between four or five years old, depending on the species. In turn, at this age they can measure between one to one and a half meter, reaching a weigh which ranges between 16 to 27 kilograms.
The reproduction process begins, when the female expels its small eggs in the open sea; this action is known as spawning. These species set a specific place to carry out the spawning, this means that if they keep swimming, they will return to the initial place for getting reproduced.
The female is able to expel about 6 million eggs in a single spawning, this depends on the size of the species. Due to their big size , they have the capability to create huge amounts of eggs inside their bodies. Now, once the eggs are in the water, they will only be fertilized when the male expels his sperm to the sea in order to fertilize them. As a result ,small larvae emerge from these eggs in the next 24 hours.
Now, the main characteristic of these small eggs is that they only measure a millimeter in diameter. Moreover, they are also covered by a kind of oil, whose function is to help them float in the water while they are fertilized. From the moment they are born until they reach adulthood, tunas can grow up to a billion times more than its initial size.
It is also important to note, that only a couple of larvae of the millions that have been produced, reach a state of adulthood. This is because they are so small, thus they are prone to be devoured by much larger predators at sea, even by others tuna fishs.
So, usually these larvae face big threats that not all surpass, resulting in only two individuals in average, capable of overcoming this fate and avoid being eaten by larger animals.
Alimentation Habits Of The Tuna Fish
Tunas are characterized, by carrying out intense physical activities; so they need to eat in the best way to recover the energy 
lost when swimming. Therefore, their alimentation is based on some species of fish, crustaceans and some mollusks. It is also important to know that they consume large amounts of food, which equal in most cases to a quarter of their own weigh per day.
In addition, and because of their swimming skills, they have a big advantage to follow and hunt their preys without much effort; they just need to apply a bit of speed. For this reason the tuna fishs feed on whatever prey available in the surface where they inhabit, since they are skilled predators of smaller species.
Habitat
Regarding their habitat, tuna fishs tend to live in warm waters, where the temperature ranges between 17° C to 33° C. Moreover, these fish are known for inhabiting in open sea. The majority of tuna fishs, remain in the upper layers of the ocean, which is to say, in shallow waters of warm temperature, where the currents of the sea are a bit more intense. They find at this depth the best options to feed on.
Finally and according to specialized studies, these fish tend to swim in group.
Now , let´s keep learning about this wonderful species…
Most Known Species Of Tuna Fish
Following, we list the most common types of this specimes
Common Tuna Fish
The scientific name of this fish is Thunnus thuynnus, and they are also known as blue fin tuna or red tuna. These specimens measure a maximum of three meters in length, and in most cases they weigh about 400 kilograms, even there are individuals which reach up to 700 kilograms. The common tuna, make migration journeys for reproductive purposes, and this process is carried out in summer where the water temperature changes. This journey takes place in the waters of the Mediterranean Sea .
White Tuna
In this case this species receives the scientific name of Thunnuh alalunga. Another name that is attributed to this species is “bonito del norte”, however there is no relation between these fish, and the “ bonito fish” .
These specimens are characterized by having a strong body and a big pectoral fin, which make them a little different from others tuna species. The white tunas measure about 140 centimeters, and weigh about 60 kilograms.
According to several statistics, and because of its delicious taste and the consistency and texture of its meat; the white tuna is the most pursued and fished of all tuna species. Moreover, in order to avoid damage to this fish, it is caught with hook. They live in shallow tropical waters, in mild oceans and at the Mediterranean sea. The “bonito del norte” is the one fished at the Cantabric Sea.. So it is an important part of the trade of the tuna industry.
According to specialists, this species is currently in a good state of conservation that presents a low risk; however there are several threats against them , that should be regulated by the pertinent authorities.
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Yellow Fin Tuna
This is another popular species of tuna, whose scientific name is Thunnus Alba-cares. This animal is distributed in shallow tropical waters around the world. In terms of its size it can reach 239 centimeters, and its weigh is around 200 kg. This species is currently in a state of preservation, that represents a low risk.
Unlike other species of tuna, the yellow fin tuna has an stylized silhouette, but its head and eyes are smaller. At the same time, they are also characterized by having longer second dorsal and anal fins.
On the other hand, they are also known for presenting blue and yellow colors; in the lateral bands located in their dorsal area. Their belly is silver in color, with small vertical stripes which are alternated by points. Their second dorsal fin and the anal fin also present yellow tones, which give them their distinctive name.
This animal is abundant in the waters of the Atlantic Ocean. Usually the youngest individuals live near the surface forming a schoal of fish, while the adults prefer to swim in slightly deeper waters.
Big-Eyed Tuna
This species in the same way as the previous ones is very common, it is known by its scientific name as Thunnus obesus.
Currently it is in a vulnerable state according to the danger of extinction. In many regions of Spain it is known under the name of “patudo”.
In terms of size, they reach a length of 250 centimeters and weigh around 210 kilograms.
It is important to note that unlike other species these fish are not found in the Mediterranean Sea, they are scattered in the shallow waters of the Atlantic Ocean, the Indian Ocean and in some areas of the Pacific Ocean.
Properties Of The Tuna Fish
It is important to known, that the tuna meat is in pink even red when it is fresh with a compact texture. According to several researches this meat contains considerable amounts of hemoglobin, around 380 milligrams per 100 grams of muscle. In addition, it also has myoglobin, this in an amount of 530 milligrams per 100 grams. No doubt these are the most important contributions in relation to the properties of tuna.
But on the other hand, more components are also known. In 100 grams of tuna there are about 23 grams of protein. In turn, it has about 6 grams of fat; this amount varies depending on the area of the body where the muscle comes from. The spine of the tuna fish has few fat, and the ventral area has about 28 grams of fat.
In spite of being a fatty food because of its properties, this fat is healthy; since it contains omega-3 fatty acids.
In addition to the above, the properties of tuna also include several vitamins and minerals. On the other hand, it also contains several vitamins of group B, specifically B2, in greater quantity vitamin B3, and also vitamins B6, B9 and B12. These contents exceed the properties that contain red meat, eggs and cheese. In addition, it also contains vitamin A and D.
Continuing with the contributions of only 100 grams of tuna, it can be said that it has significant amounts of minerals such as phosphorus and magnesium. These stand out among their properties, since they have about 200 milligrams of phosphorus and 28 milligrams of magnesium. In turn, we can´t leave aside the contribution in iron and iodine. In the case of iron per 100 grams of tuna there are 1.3 milligrams of this component, and on the other hand in the case of iodine there about 10 milligrams, which in the same way bring great benefits to the health.
Benefits Of The Tuna Fish
Because of its high amounts of omega 3, consuming tuna is beneficial for health, since this component significantly lowers the high levels of cholesterol in the body, resulting in an improvement in cardiovascular health. This prevents problems such as the risk of atherosclerosis and thrombosis.
On the other hand, its content in vitamins allows to assimilate in a better way; the other nutrients that it also contains, such as fats and proteins. In addition, the presence of B vitamins in the body encourages the formation of red blood cells; which is quite useful for to the nervous system and the defense of the organism against bacteria.
Moreover, vitamin A keeps everything related to the different tissues of the body in good condition, such as its growth and development. It also contributes to the improvement of vision and it is important for the health of the nervous system, preventing possible infections. Other benefits of vitamin A is that it increases the health of the bones.
As far as vitamin D, it can be said that it favors the entire process that involves the absorption of calcium; and its fixation in the bones of the body; in addition to regulating these levels of calcium in the blood.
On the other hand, the phosphorus that is present in the tuna, also brings health benefits, as improvements in muscle activity, the nervous system and it intervenes in the processes of obtaining energy in the body. The health of the teeth is also benefited after consuming phosphorus.
In relation to the above, the tuna´s important contribution in magnesium, brings benefits such as improvement in all organs that are part of the digestive system, including some muscles and even some nerves. The magnesium also contributes to the health of teeth and bones in general. This component improves the immunity of the body against possible infections, and in turn has a subtle laxative role, which helps eliminate bacteria.
It is important to know, that the iron provided by the tuna also brings big benefits for health, since the iron is necessary to generate hemoglobin, a protein that has the important function of transporting the oxygen present in the body from the lungs to each of the cells.
Finally but no less important, it is necessary to take into account the benefits of iodine, since this mineral is fundamental to improve everything that involves the functioning of the thyroid gland, which has the purpose of regulating all metabolic processes.
However, we can´t take advantage of all these benefits, without learning first how too cook this fish..
Consumption Of Tuna Fish
Regarding its consumption, tuna is very popular in gastronomy worldwide, there are many countries that consider this fish as a paramount in their gastronomy, so that its consumption is very high. In turn, the trade of tuna in the Asian continent has increased the development of this market worldwide. We have the specific example of Japan, that has impacted worldwide with their popular dish sushi.
The available data in relation to the tuna fishing confirm, that only for the year 2007 four million tons of this fish were captured. There is no doubt about this figure is alarming, since with the passage of the years it has increased continuously . In relation to the previous data, the studies showed that only 70% of these catches were made in the Pacific Ocean, in turn, 9.5% belongs to the Indian Ocean and the other 9.5% of the fishing was in the Atlantic Ocean and part of the Mediterranean Sea.
On the other hand, the species that is most common in this type of fishing is the “ atun bonito” of striped belly, known by its scientific name as Katsuwonus pelamis, this represented 59% of the fishing. Another common species that was caught, was yellow fin tuna, which belongs to 24% of the total number of fishing.
Undoubtedly, due to the characteristics of its cuisine; the main consumer of tuna is Japan, because this fish is among the main ingredients of its most important dishes. Moreover, Taiwan, Indonesia and the Philippines, are also big consumers of tuna fish.
Threats Against The Tuna Fish
There is no doubt that the huge tuna trade and fishing industry, has negative effects on its conservation and integrity as a species. At present the species with more dangers and threats is the red tuna also known as giant tuna. The main reason of this fact; is the brutal fishing pressure exerted by the demand for its consumption. According to the data available regarding this species, the reference states that the population of red tuna has been reduced by 90% ,in the waters of the European Atlantic. As far as the waters of the Mediterranean Sea, the population of red tuna has been reduced by 50%.
A study with data from the International Commission for the Conservation of Atlantic Tunas (ICCAT), states that the complaint is based on the fact that only in the year 2007 fishing exceeded 60 tons. This is twice the amount allowed by the competent law, and it is a number that exceeds four times the ideal amount according to ecological sustenance.
On the other hand, in relation to the worrying numbers that the study shows, it is known that the European Union has not yet banned the fishing of red tuna in Mediterranean waters. In the same way, the fishing quota hasn´t been limited as much as it should be. The purpose of the complaint of the ICCAT in conjunction with a group of ecologists, is to reduce the 20,000 tons per year to a number of 13,500, or in the best case, to eliminate the permit for the fishing of this species.
As far as, this Japan is the country responsible for a quarter of the fishing that takes place around the world; since it is in this country where the largest consumption of red tuna is carried out, due to sushi as the main reason. Trade increases prices , which further encourages illegal fishing of this species. We have the reported case in 2009 , when 137,000 euros were paid to for a single red tuna fish; that came to weigh about 202 kilograms. This type of action is fought by the International Commission for the Conservation of Atlantic Tunas and the main environmentalists.
In addition to these facts, the red tuna has to face the contamination of the waters where it carries out its reproduction. There are data that assure that breeding centers have been decreasing over the years, since the oil industry contaminates the areas where red tuna migrates to reproduce. This entails serious consequences in the reproduction of this species, since the spawning area becomes a totally toxic environment.
On the other hand, in the case of the larvae, because of their small size and lack of strength; they do not have the ability to flee to avoid contamination by the hydrocarbons. So they will keep swimming , along with these toxics substances by the current, which entails their death.
It is important to note that tuna schools attract fishermen and hence tuna fishing, however they are also a
wonderful sight for those who love nature and seek its preservation.
However many options have been developed in order to solve this situation…