Recently, I discovered something wonderful: merperson bones. Merperson skull totems, at base quality, are worth 500- which means that a masterful one would be worth 6000. When you're living next to a good-aligned ocean, merpeople are a renewable resource: the only problem is catching the darned things. Thus far, I've only recovered the corpses of beached merpeople who drowned on shore. So, here's the challenge: help me design an apparatus which will allow me to catch and slaughter merpeople in a fashion which guarantees recovery of the remains!
Now, this is what I have in mind: an underwater funnel, leading to cage traps and sealed on both ends by floodgates, with pumps on top to drain the funnel. Catching the merpeople alive would be optimal, because recovering cages is not as time sensitive as recovering corpses, so I could drain whatever underwater trapping area I'd used at my leisure and drown the things on land to get at their precious internals. Breeding them would, unfortunately, be somewhat impractical, as they have only single children and take 12 years to mature...
The funnel:
770╗777777777777777
777╚═╗7777777777777
77777╚═╗77777777777
7777777╠════════╗77
7777777█^^^^^^^^█77
7777777╠════════╝77
77777╔═╝77777777777
777╔═╝7777777777777
770╝777777777777777
Either or both walls of the thin funnel should have screw pumps mounted to drain the thin passage of water if and when the traps are triggered, and the floodgates should be left open at all other times. I've had relative success using such funnels in terrestrial trapping, but in those cases there was the added inducement of a drafted peasant chasing the animals in question. I have no idea if an unfrightened animal tries to find a path to a specific destination, or moves totally at random choosing from available adjacent squares- in the case of the former, the funnel channels the creature or creatures from a broad area into a narrow area with good reliability if the creature can be got into the broad mouth of the funnel with sufficient inducement to keep moving, while in the case of the latter one imagines that the funnel may have no effect at all, or even an adverse one... anybody with greater insight into the movement of creatures could help me with this aspect of my problem. If unmolested creatures move entirely at random, something more like a "roach motel" with a great many entrances might be more appropriate...
But at any rate, building the darn thing is going to be quite a challenge in itself- any experienced ocean-builders have good advice on doing something like this?