You shouldn't be greedy when fishing.
Zach runs a crab fishing boat and has been out catching crab on the ocean for days, and the crab in the boat are not healthy.
Zach wants to catch more crab.
Zach catches crab for a few more hours, then decides that he needs to drop off his load.
Zach catches crab for a few more days, ignoring the sick ones.
The crab all survive and Zach gets a healthy payment.
Some crab die, which causes other crab to die through dead loss, cutting Zach's profits.