The overlarge barb is one of the serious causes of losing fish. Often you may hook a nice trout, play him a while, & then suddenly find the fly coming toward you and the fish going in the other direction. 8 times out of 10, I assure you, the barb of your hook was not deep enough into the fish’s flesh. You simply had the point of the hook stuck into him up to the barb. As long as there was a fair amount of tension on your line it held him, but as soon as he got slack line he was able to eject the fly. Any hook that is set over the barb into that grizzle or tough flesh is not going to be dislodged very quickly by any trout, even if he does manage to get slack line. Most hooks sold today have a barb so wickedly big that, even if you do manage to set it into a fish’s jaw without breaking your…leader, the barb makes such an enormous gash or hole when it enters that it becomes as easily dislodged as a hook which has not penetrated over the barb.
The Art Of Tying The Wet Fly by James E. Leisenring