Were the mates superfluous in the whale boats?

I was a little surprised whaling crew seemed a bit more tolerant of difference than I expected for the time and place. The crew is multi-racial. Next to the captain and the 1st, 2nd and 3rd mates, the next highest ranking crew were the harpooners. One was a Native American, one was a West African and one was a New Zealand Maori. In one chapter, Melville criticizes the way the boats go after the whales. The harpooner is expected to row like mad with the other four rowers while the mate steers the boat. When they close in with the whale, the harpooner has to stop rowing, get up and throw his harpoon at the whale. Then he changes places with the mate and the mate finishes off the whale by repeatedly stabbing it with a lance. Melville thought this was inefficient as the harpooners often missed because they were exhausted from rowing. He thought the harpooner should not have to row, but that after throwing his harpoon at the whale, should proceed to finish it off with the lance. I wonder if the reason they did not do this is because it would transfer too much status from the mates to the harpooners, who were, after all, just savages, recruited from around the world for their ability to throw a spear with great power and accuracy. You cannot have two crew members out of six not rowing, and what would you need the mate for? Maybe it was not a question of racism, more the officers seeking to protect their own prestige.