If you need a small harpoon option for land-borne survival (small fish) check out m40's ten-cent survival knife,
http://www.m4040.com/Survival/10_Cent_Survival_Knife/10_Cent_Survival_Knife.htm My son make be one and now it is with me in the ubiquitous Altoids tin along with a few other things. Just a thought.
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"Its not a matter of being ready as it is being prepared" -- B. E. J. Taylor