If this question is about “Ode to Large Tuna in the Market” we can see that for the author, tuna means the finitude of life. This is because the driver is amazed at how tuna was once a strong and vigorous fish, which overcame the adversities of the sea fudge and was full of life, but was surprised by the finitude of life and the feeling that everything comes to end.
With this, the author shows how the struggles and all the vigor we have in life are insignificant, since our life will end anyway.
