Summarize:

Professional fishing spears are sold at most sporting goods stores. Find the straightest branch you can and carve the tip to a sharp point with a knife if you have to make a fishing spear.  Green willow wood works best if you have to carve a spear, but any strong, straight branch will work. Try to find a branch with 2-3 prongs at the tip you can carve into a trident to snag fish more easily. If you buy a professional spear, you can even get one with a launching mechanism, like a speargun or a bow with fishing arrows. This method only works for catching large fish. It requires a lot of skill and patience. Stand somewhere where any light won’t project your shadow onto the water. Your shadow will scare away fish and make it hard to spear any.   Pick a spot near shallow water where you will be able to easily spot fish as they pass by. You can also spear fish at night with a flashlight or headlamp. Aim for the base of the head where it connects with the body to kill the fish immediately. Pull the spear back to you with the fish hooked on the end once you have speared one. This will take a lot of practice and patience. You will also need to learn to adjust your aim because water refracts light and causes the fish to appear in a different location than that which they are actually in. You need to aim lower than you think you do, so shoot just under where it looks like the fish is.
Buy a fishing spear or carve one out of a branch. Find a place on the shore to hide your silhouette from passing fish. Jab your spear at the fish as they swim by.