code/modules/fishing/sources/_fish_source.dm

/proc/init_fishing_configurations	These are shared between their spots
/datum/fish_source	Where the fish actually come from - every fishing spot has one assigned but multiple fishing holes can share single source, ie single shared one for ocean/lavaland river
/proc/collect_fish_properties	Awful workaround around initial(x.list_variable) not being a thing while trying to keep some semblance of being structured