Actually, I would personally approach it as a tech skill; I'm not using the spear as an extension of my body, I'm using it as a tool with which to catch fish; to compare it to a fishing rod with a mechanical reel or a harpoon gun, both of which are clearly tools used to catch fish.
On bod biases, most Earth-type worlds have a 12@ bias level (I believe) to account for abilities indigenous creatures but not humans have (metamorphosis in caterpillars, tadpoles, etc).