So the faster and more ships your team can unload, the more you're paid. That's the incentive.
I once got paid almost $1000, in just one day - but that day was 20 hours long, and you're pretty much beat to a pulp afterwards.
We had people come in, and leave before lunch. No pay in the world would keep them there.
Edit, for the curious - I tried to look up some footage of what it looks like:
This clip shows a nice and modern trawler, the unloading requires little manpower. See those long brown blocks on the palets? Those would be around 40-50 kgs / 90 - 110 lbs. https://youtu.be/Qi7VNBOJetA?t=115
This is more on par with what you'd usually see - the rooms would be stack to the ceiling with frozen packet/blocks. Those blocks are around 20 kgs / 45 lbs each. https://youtu.be/e7u-X8XR1hs?t=543
Here's a larger trawler - again - sometimes the fish will be stacked to the ceiling https://youtu.be/fQEwECzZL_s?t=2739
Unfortunately I can't seem to find any footage of the more usual scenario, where the blocks are just piled up at random.