I turned in the quest “Dragonsprings Drop” at the Roaring Dragonsprings Fishing Hole. I only saw the two quest givers, the repeatable from Daring Fisher and the “grab fish and drop 'em” from Thrifty Fisher.
My assumption here is that doing “Dragonsprings Drop” is supposed to unblock the second fishing net spot since there is no goblin questgiver at the Roaring Dragonsprings Fishing Hole, unlike the River Mouth Fishing Hole in Waking Shores.
12/15 Update: “Predator Control” from Thrifty Fisher is what unlocks the second net. For whatever reason (despite being “Rich”), it wasn’t offered yesterday. I turned that quest in and was able to set the second net.