The collapes of industry and nosediving population would lead to a huge resurgence in the fish population, which could be "hunted" with no noise, no real expenditure of calorie or effort, no need to protect crops from marauding humans, etc..
I take the phrase “omnivore” literally. Vegans obviously are grazing livestock, so come the Zombie Apocalypse, we’ll just eat them.
Vegan. It’s the other white meat.