By-Catch is not some sports guy out schlepping fish to commercial
(boat's) interest's.

By-catch is a term used in the fishing industry for the incidental catch
of a non-targeted specie's.
Let's say I'm out bottom dragging for flounder in the NY Bight, I haul
back my net and empty it, and lo and behold there in my pile of
flounder I wish) is a juicy 2lb lobster, Well thats By-Catch.
BTW, That By-Catch was served with lemon and butter! UD