. Any tips on the most productive way to use it? Jug fishing or staked by the margins?
i have seen them used in USA where they are tied to a strong branch hanging over the water, you can extend the cord by attaching fishing line to it if needed, they are then baited and set with the hook in the water at what ever level you require, the fish gets the bait and pulls the line, this releases the spring holding mechanism which then in turn allows the coil spring to "wind in" the fish, they will very easily lift the fish from the water, so allow for this and where possible check them every 2-3 hours, or they will dry out and start to turn rancid in the sun etc etc...
as a survival tool they look a very good investment and would be most useful....
hope this helps.
chris.