Poseidon, as the god of the seas, held great power and significance for the ancient Greeks. He was patron god of sailors and fishermen, whom seafarers and fishermen prayed to, when they went out to sea.  The tuna fishermen prayed for a good season, prayed for  an abundant catch, for successful pursuit of the tuna and consecrated tuna offering to him in his temples.


Athenaeus, Greek rhetorician and grammarian, (2nd-3rd centuries CE) in his chief work  Deipnosophistae (Dinner-table philosophers) describe sacrificial offering of tuna to god Poseidon:

The people of Halae (ancient Greek town in Boeotia), when they celebrate a festival to Poseidon in the tunny season, offer to the god, in the event of a good catch, the first tunny caught; and this offering is called a thynnaion (tunny offering).

The tuna fishermen prayed also at the crucial moment when the tuna have been caught in the trap, but not yet brought out of the net. Claudius Aelianus (ca. 175-ca. 235), explains why the fishermen pray to Poseidon at this crucial moment when they remove the fish from the nets:

When Tunny have been caught by fishermen of the Euxine,  when they are safely enmeshed in the net, then is the time when everybody prays to Poseidon. They pray to the brother of Zeus, the Lord of the Sea, that neither swordfish nor dolphin may come as fellow-traveler  with the shoal of Tunny. Sword-fish has many a time cut through the net and allowed the whole company to break through and go free. The dolphin also is the net's enemy, for it is skilful at gnawing its way out. (Aelianus "On the Nature of Animals")

This ancient authors reminds us how much the Greeks attributed to the Poseidon in their successful pursuit of the tuna.