A crayfish are lured in by carrion secured to the bottom of the crate.
B Upon arrival, the crayfish crawl in through the one-way trap gates.
C Or they climb up.
D Arrived at the top, they fall down through the hole.
E After eating the bait at night, they find no hiding place in the crate during the day.
F In case of panic, they will occasionally try to shoot backwards, but since lobsters almost never do so vertically, in most cases they will bump into the side walls or against the overhanging top edge of the crate and return to the bottom.
G Ultimately, the crayfish will likely settle around the edges of the bottom of the crate.
H The trick now is not to collect the caught crayfish, but to leave them there. On the light bottom of the crate, the lobsters are then in full view of cormorants, grebes, coots, pike, bass, eels, otters, brown rats and muskrats swimming over during the day. These can freely swim in and out of the tank through the large opening, to easily catch the crayfish, because the chance of escape for the crayfish is very small in the crate. In addition, the trapped larger crayfish are expected to eat the trapped smaller crayfish so that the problem will partly resolve itself.
I Due to the stick protruding above the water with the characteristic flag, the crate above water is very recognizable for humans and animals. My expectation is that the smarter predators will quickly learn to recognize the crates as a food source (“Those sticks give easy to get food!”), which increases the effectiveness even more.
1: The risk for the predators to get caught in the tank themselves, as often happens with fish traps and other traps, is very small because the opening, where all the light comes through, contrasts strongly with the dark, overhanging edge of the crate top. In addition, almost all predators are much more intelligent than the simple lobsters. Pike and grebe may be less likely to swim into the crate, but that doesn’t seem to be a problem for perch and eel, as they are used to hunting and hiding in cavities. I wouldn’t be surprised if the ubiquitous coot eventually turns out to be the prime “lobster crate profiteer.”
2: In this way these bins can remain in place for a long time without having to be checked often. Slightly clear water may be quite important.
3: It will have to be tested whether the bycatch will indeed be minimal, that straight walls will possibly work as well as sloping walls (this saves production costs, because then the crayfish crates can be made from old laundry baskets and old PVC bins), how often bait will have to be refreshed (due to the pole system, applying new bait is less labor-intensive) and to what extent the trap holes on the side contribute to the catches (the hole at the top may be sufficient).
4: Many small crayfish will also be caught through the large opening at the top. Due to the lack of openings on the sides, these little ones will not be able to escape, as is the case with many traps and baskets.
5: Humans can also be counted among the predators that can eat from the crayfish crate. Poachers or people who want to get hold of a meal of lobster are not a problem in that sense, but part of the solution.
6: As a possible bycatch I expect eel, but this one eats a lot of crayfish and hopefully it will swim out of the hole in due course; if not, an upside-down trap opening can be made in each top corner of the tank to allow the eel to escape again. In addition, possibly exotic gobies and locally perhaps bullheads might get caught. This possible minimal by-catch is unlikely to be a problem for conservation or fisheries.
7: The crates must be properly weighted, so that current, storm and theft will not move them.
8: It may be more effective to use two flag poles to make it easier to change the bait (just drop it between the poles) and to make it easier to lift the crates out of the water. For the latter, handles can of course also be made on both sides of the top.