OCEAN FISH DYNAMICS Class OSTEICHTHYES (PISCES) Subclass ACTINOPTERYGII Superorder TELEOSTEA Order PERCIFORMES Family TUNNIDAE Thunnus thynnus Also > 400 cm length > 650 Kg weight Eyes, mouth, and head, large and evident

Two different populations in the North Atlantic BFTW reproduction area, the Gulf of Mexico BFTE reproduction area, the mediterranean Sea The tuna fishery in the Mediterranean exists from 6,000 y BC

In both Mediterranean and Gulf of Mexico, tuna came back from all the Atlantic to already known reproduction areas For feeding tuna go wherever they find biomass to eat. (generally water front areas)

After fertilization of eggs, juveniles reach 1 cm in 10 days They are not able to move over geographical areas They have been found in all the regions of the Mediterranean but Alboran, Lion, Ligurian, N Adriatic, N Aegean

From 200 years juveniles of < 1000 g are collected in any part of the Mediterranean in the period July-October Larvae are initially lecitotrophic They became planktotrophic after 3 days They feed on copepods Large mouth and eyes, they are predators also by juveniles Adults prey mainly on anchovies; they reach 300 Kg at the age of 15 y

The adulthood is reached at an age of 8-9 (Atlantic population) or at 3-4 (Mediterranean population) Adults are commonly found out from their reproductive areas, and down to -1000 m C

Tuna avoid river deriving water Support 3 < T < 30°C They eat about 10% of their bodyweight every day A relatively large heart Large amounts of Mioglobine Capillary net Vascular system and bodymass good to maintain the body temperature up to 10°C over the external environment

Tuna have not a good (large) gas bladder The swim is based on Discontinuous accelerations Hydrodynamic bodysize Gregarious behaviour

Atlantic bluefin tuna belong to two separate populations Different age of adulthood Different spawning areas Different migrating behaviour Those in the western Mediterranean migrate also in the East Atlantic Those in the central Mediterranean migrate only inside the Mediterranean

FISHERY Fenicians: mobile nets (1000 BC – 700 AD) Nowadays Flying nets Palancari Sport fishing Bizantines: fixed nets (700 AD) Hohenstaufen: tonnare in Sicily (1200 AD)