Making a Fishing Spear-Bushcraft: American Wilderness: This is a step by step visual of making a fish spear from harvest to completion (without barbs).
Spear fishing with an atl atl: Primitive Hunting: This starts with making a primitive bone spear point- made all primitively. Then demonstrates successful hunting with the spear and atl atl.
Night Spear: Aboriginal Hunting and Spearfishing in Remote Australia: Fishing the Wild This video demonstrates spear construction (using some modern items, but they describe traditional spears). They also demonstrate fish spearing with an atl atl (has a different Aboriginal name) and by hand with throwing techniques. They also fish at night, which might have applications elsewhere as well.
How to Make a Fishing Spear- Hedgehog Leatherworks This is a good article with step by step instruction including photographs. Note, however, how large the head of the spear is (how far apart the tines are). This would not be useful for many average sized fish. He could either use smaller dividing sticks, or make the split less deep- not pushing the tines are far apart.
My Pinterest Collection on Fishing– not just spears and bows.