backing down hard is only done with trying to fight a fish on very lite line test (4-8lb test). Its a ridiculous practice and more about the abilities of the captain to run over the fish. The angler just winds. It really beats the hell out of a boat. The object is to grab the leader which signals a caught fish. Most fish at this point don't even know they are hooked and are super green.
In this instance, the captain didn't have a kill lanyard...when he fell the boat just kept digging in...nice fish they had on though. Great pic of the captain falling off the tower at the end.
As for keeping up with a fish going backwards...you really don't do that either, you try to keep the fish tight (line to the reel) and off the backing (most reels have two different lines connected to make one line). Backing is the bottom line on the reel. You want to keep the fish behind the boat but not under. You can only back down as fast as someone can reel in the slack without letting any slack in the line. If that makes sense...