One way to harvest fish is with a spear. Unless you are in a survival situation spear fishing is pretty well limited to non-game fish, so if you want to practice spear fishing make sure that you do it in a legal manner. Pictured below: Fish spears
One thing that we have going against us in East Texas is that there is not much clear water. It is usually pretty hard to see fish in our mud bottom rivers and lakes. One time of the year when spear fishing, or bow fishing, is popular is in the spring when the Gar are spawning.
These big fish come up into the shallows and roll on the surface of the water in spawning season and are an easy target for a spear. The main problem with spearing Gar is that they have a very tough skin. Early Spanish explorers referred to them as "the armored fish" and Native Americans actually used the dried scales for arrow points. So if you are trying to spear Gar, make sure you have a sharp and durable spear.
I have three fish spears. One is the kind that you can buy at hardware or sporting goods stores. You just buy the spear head and then attach it to a wooden shaft. Pictured below: Fish spear with store bought point.
I have another spear that a friend of mine made for me. The shaft of this spear is a sealed hollow tube, so if you drop it in the water it actually floats back up and about a foot of the shaft bobs up out of the water. Pictured below: Floating fish spear.
I have a survival spear that I made out of a Hickory sapling and some Yucca cordage. To make this spear I cut a small Hickory tree, and while it was still green I split the smaller end into four pieces. I wrapped cordage tightly around the bottom of the split section to keep it from splitting any farther. I then placed small sections of dried limb across the bottom of each split to spread the barbs out. Some more Yucca cordage was added to hold the barbs together above the wedges. I used my knife to taper and shape the barbs. Pictured below: My survival fish spear.
One thing that you have to keep in mind when you are spear fishing is that the fish is not where it appears to be. Because of the light being refracted by the water, the fish is actually closer to you than it appears. I've read all kinds of formulas for calculating where the fish is, but I don't see myself doing the math fast enough to spear a fish. It's one of those things, like instinctive archery, that you just have to practice.