For everybody who does the mackerel run, how long on average does it take to catch the mackerel? I just did two runs, one was 18.25, the other was 37.43. Am I just really unlucky? Or does everyone have a lot of runs like that?

Sometimes you can get them first try but catching them in general is only just above 4% chance: https://docs.google.com/spreadsheets/d/1UO1Z8ia5qweHh6vnNRayWA_4A-uO7sdQfYGA8y8F4jo/edit#gid=0

Also, most of our runners are very active on the NieR: Automata speedrun discord, which you can find by going to http://discord.nierspeedrun.com or clicking the "Discord" link in the sidebar to the left of this writing.