This achievement can be annoying due to a glitch/oversight in the game. The problem is that the line is only around 223 yards long and if a fish reaches that distance, the pressure on the line increases until it snaps. Unfortunately Le Lac d'Or is a very big lake with several large catfish and carp that can easily take you to 223 yards.
The way to get around this is to fish towards an alcove so any fish you hook will run into a dead end. The video below shows where I caught all my larger fish.
Ideally you will want to use the 30lb line and a 13ft rod for longer casting distance. The 20mm sinking Tiger nut seemed to be the best bait for large catfish on a size 4 silt hook. Other baits such as Active 8, Milky Toffee and Tane boilies also worked.