Man is not the only being on the planet that has adopted the habit of following routes to survive. Tuna also have one which they have traced for centuries and centuries: from the Atlantic to the Strait of Gibraltar, to reach the warm waters of the Mediterranean and deposit their eggs, always following the same course.
Tuna has been a symbol of prosperity since prehistoric times: its meat rich in protein, essential fatty acids, potassium, selenium and vitamin B12 has been processed by man since time immemorial and nothing is thrown away. Garum, for example, is a sauce made of the eggs and innards preserved in salt dating back to the first century AD.
The Atlantic Bluefin tuna, Thunnus thynnus, is the most sought-after variety: a large fish with a steel-blue back and silvery-white belly that reaches up to 3 metres in length and 700 kg in weight. Their slender body and strong musculature allows them to swim rapidly over long distances.
Their natural habitat is the Atlantic, where they live in deep waters that they leave each spring, when it is time to reproduce and warmer temperatures are required. And so begins the outward journey, always identical, accompanied by the group: the Balearic Islands, Sardinia, Sicily and in some cases even straight on to Turkey. Then later the return from east to west.
The fertilised eggs give rise to rapidly growing fry: in a year they can reach 70 cm and weigh up to 5 kg. But only when they reach about a metre in length and weigh at least 15 kg can they be said to have reached sexual maturity. That is why it is important to give them time to grow, so as not to limit the population. Which is why tuna under 30 kilos cannot be fished in Europe.