Depending on the size of the survival kit, I think you're right that longer and stronger line and more hooks will get you more food. Plus it would give you the option of setting up a trot line. More like trapping then hunting. For a smaller kit, I would still include more then ten to thirty feet, 100 at least. For the same reasons. Also, in a small kit, if you can make the fishing line and the thread the same, you can eliminate an item. Not very fine thread, but needles come in all sizes and field repairs can have Frankenstein stitches as long as they hold.