An Ironic Ending

I found the ending of The Old Man and the Sea to be extremely ironic. I did get part of my wish with the whole shark attack thing. Santiago was actually attacked by several sharks. At least, his boat and fish were attacked. I kept thinking while the marlin was getting attacked "Wow. Santiago goes to all this trouble to catch this fish, and it gets attacked by sharks. That is quite unfortunate." Like I said, Santiago gets pulled along by the marlin for two days and then on his way back home, dead marlin in tow, a whole slew of sharks attack the boat. I felt kind of bad for Santiago, because chasing and then killing the marlin almost killed the old man. He worked hard to get that marlin, and because of sharks, he is not able to collect his necessary payment when he arrives back home.
What I am wondering is why Santiago did not attempt to cut up the marlin on his boat and transport the marlin home that way. I understand his boat was a small skiff, but he should have been able to cut the fish up in my opinion. That way, the old man would not be leaving trail of fish blood and guts saying come and get it! Freshly caught marlin! However, I get that the fish was extremely heavy and the marlin would be exceptionally difficult for the old man to pick up. But, if the old man was able to jab a harpoon into the fish and kill it, he should be able to lift the fish up into the boat and cut it up without sinking his skiff. As it ends up, the sharks attack the dead marlin, and the old man has to attempt to fend them off. I just do not understand why the old man would let the sharks feed off the marlin before he killed them. Santiago is just too kind in my opinion, which can be a good thing.