After patch 7.1, Darkmoon Daggermaw is the currency for a brand new mount, the Darkwater Skate. This mount costs 500 fish, and they are very easy to fish up on any water surface on the Darkmoon Faire island. However, people are not too interested in fishing, and a lot of people will therefor buy the mount by purchasing Darkmoon Daggermaws from the auction house. This can be used to your advantage when you want to make some easy gold!
Each fishing cast yields one Darkmoon Daggermaw, and most catches get one of these, with the exception of the low drop chance crate, which drops a lot more of them. You can easily fish up 200 of these per hour, and on most high populated servers they are worth around 100g per fish now, which means 20k gold per hour. With some luck you will get even more than 200 per hour.
If you want the details on how to farm them, check out the Darkwater Skate mount guide by clicking here.