The "tonnare" of Trapani have been the most important ones in the Mediterranean Sea for centuries. Tunas fished are the largest because they come at the end of the migration.

The job of the "tonnaroti" (tuna fishers) begins in April when they drop a number of nets in the sea: such nets can be 4-5 kilometers in length and they form many "rooms" which induce tunas into penetrating the most internal nets more and more until they reach the so-called "camera della morte" (room of death).
May comes and the boats depart from the "tonnare", lead
by the "Rais" to the "mattanza" (massacre). This operation is performed by slowly pulling up the nets and exposing the caught tunas which will then be picked up through the use of piercing harpoons, dropping abundant blood in the process. This kind of fishing is disappearing because the tunas are decreasing due to the sea pollution and the industrial fishing which intercepts the schools of tuna fishes before they reach the coast.

The "mattanza" is an extraordinary event in which the killing of huge fishes is not a gratuitous show of violence such as the Corrida is: in fact the "mattanza" answers to specific social and economical needs, since
hundreds of family depend from a good season of fishing (businessmen, fishers, scavengers, caterers and hoteliers due to the appeal the "tonnara" has over tourists and ethnic-anthropologists).

The oldest "tonnara" still operating in Italy is located in San Giuliano/Bonagia (first proofs date back to 1200) and one can watch fishing operations which have not been transfigured by the tourism business: the "mattanza" is still the same as in the past centuries and it seems like time has frozen over the delved by sun faces of tonnaroti, still singing the traditional "cialome" songs which accompany their hard work.
Net-fishing of tunas has very ancient origins (Homer mentions it in the Odyssey): "tonnare" were operating basically in every Italian coast, from Liguria to Trieste, being a few more than one hundred by the ending of century XIX). Nowadays besides the ones operating in Sicily just a couple of tonnare are being dropped on the Western coast of Sardinia.
Sources: Wikipedia - Ninni Ravazza

sources: wikipedia - Ninni Ravazza

Tuna is a quite large fish, characterized by a bluish back, silver flanks and grayish womb. Because of its cyan color and the fact it lives in large schools where the sea is more blue, tuna is also called "blue fish"; in the Mediterranean Sea it is also called "red tuna" because of the meat's red color; "long wing" (alalunga) or white tuna is also very esteemed. Some varietals are usually sold as fillets or slices while the so called "tonnetto" or "bonito" is sold as a whole due to its lower quality.

There are three types of tuna meat: fillets, "tarantello" and "ventresca".

The part of tuna usually sold in markets by the simple name of "tuna" is the one attached to its back. It is the lesser esteemed meat even if very tasty, it is also the leanest meat overall.
The "ventresca" is on the contrary a fatter and softer meat, being in the womb part of the tuna. It is considered a real gluttony by gourmets, sold apart because of its higher quality. It is not too much laboured usually, but it is suggested to be served with lemon or high quality vinegar.
A third type of fillet is "tarantello" which is located between head and weomb: it is softer than red tuna fillet but less fat than "ventresca" which also has the same flavor.
It is suggested as appetizer with a few drops of lemon or as main ingredient in sauces and dressings.

Tuna is a fat fish but it is also rich of proteins and mineral salts and as such considered tonic and energetic. It can be hard to digest, therefore it must be of limited intake by subjects with gout or overweight issues.

Il tonno è un pesce piuttosto grande, caratterizzato da dorso bluastro, fianchi argentei e ventre grigiastro.
Per il colorito azzurro-argento e per il fatto che, come gli altri pesci appartenenti alla stessa categoria, vive in grossi banchi dove il mare è più azzurro, viene denominato pesce azzurro; nel Mediterraneo si trova il tonno rosso, chiamato così a causa del colore della carne; l'alalunga o tonno bianco è considerato molto pregiato. Queste due varietà solitamente vengono vendute a tranci o filetti, mentre il tonnetto o bonito, striato o liscio, di qualità inferiore, viene venduto intero.