I made a new set of fishing spears a few weeks ago.  I roughly based my spear design on arrows used in the Northwest and Alaska for otter hunting.  I used 3/8 inch oak dowels for the inserts, and the main shaft is made of river cane.  I sharpened the dowels with a file.  then I drilled a hole in them and inserted a piece of metal from a coat hanger to make my barb.  I then drilled a hole in the other end of the insert, where I tied one end of my line.  I then wrapped about 20 ft of line around the main shaft, and tied the other end off to the main shaft.   My idea is that when I stick the insert through a fish, the insert will come out of the main shaft, holding the fish between the barb and the string, and I can get the main shaft and pull the fish in.  I did not put fletching on them since they are being thrown into the water.
I was hoping to post pictures of the fish I had killed with my spears, but after 5 fishing trips, I realize that I cannot hit a carp or gar with them to save my life  

!  However, I have stuck the spear tips into logs, drifts, and the mud, and with the exception of having to sharpen the points, they seem to work like I want them to.  One insert does not come out of the main shaft as easily as I would like, but a little filing will fix that.  Thanks for looking!