In The Old Man and the Sea, what does Santiago think about the pair of marlin he had hooked before?

As Santiago remembers hooking the marlin, he recalls how
male marlin always let the female marlin eat first, and so the female marlin had been
hooked. The male marlin stayed right by her, and even after Santiago had clubbed her and
lifted her on board, the male marlin, still trying to locate his mate, jumped into the
air to see where the female was. Santiago is greatly impressed by this memory of loyalty
and love and companionship, and recalls that even after the marlin had jumped he still
stayed around:

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Then, while the old man was clearing the lines
and preparing the harpoon, the male fish jumped high into the air beside the boat to see
where the female was and then went down deep, his lavender wings, that were his pectoral
fins, spread wide and all his wide lavender stripes showing. He was beautiful, the old
man remembered, and he had
stayed.

This impresses
Santiago as being one of the "saddest things" he had ever seen. This is an interesting
response, given Santiago's career as a fisherman and the way that he made his living
from the death of fish like the marlin. What it indicates is the depth of Santiago's
character and his sentimentality.