That depends on a lot of things.. the length of the cables you are running as well as the amount of watts you are pulling thought.
you can find the rating of wire online as to how many amp you can push thought what distance of what gage wire. If you are close to maxing out on the wires that are coming of distribution block going to the amps, you might want to fuse it.
The reasons you put fuses on the wire is to prevent running to much current thought the wire, which can make it hot and cause fires. If you have a decent fuse/breaker by the battery, you don't really need the fuse distribution block by the amps, but having a bit extra security is never a bad thing.
In my install i am putting 150 amp breaker at the battery and using a none fuse distribution block. But i am still putting a 15 amp fuse on the opus power supply line, just in case.