Thursday, 19 July 2012

Hermitcraft: Bottle Traps

This one isn't about practice or practicalities. It's about fun. Sue me.

It's high summer here in the planet's attic, and the kids are out of school. Most pursuits this time of year involve aquatic habitats of one kind or another. So here's a simple little project that costs nothing and pays off big in educational entertainment for all ages. NOTE: These traps are also often used on dry land to catch lizards. If you use one for this, make double sure to check it frequently and keep it out of the sun at all times. Failing this can result in a truly horrific death for an unoffending creature.

These survey traps are made from a pair of 2-litre soda bottles, and not much else. And they really work. There are YouTube tutorials galore on the subject; a "bottle trap" search there will net (get it? [Fish]-net? [Inter]-net?) a hundred vids. But I've yet to find a design as refined as my own, so I'm sharing it. (By way of credentials: I'm an old aquarist, specialising in local habitats. At one point, when I was twelve, I had six aquariums, fresh and salt, bubbling away in my bedroom.)

The massage:

1. Remove the labels from two clean 2-litre soda bottles. They can be round New World bottles or square Old World ones. Clear plastic works best; others will also do.

2. Cut the bottom off one, neatly and carefully. Scissors work best, after making a small starting slit with a knife. Discard the bottom, or keep it for studying collected specimens and infusoria. (Very handy.)

3. Cut both the bottom and the top off the second bottle. Set aside or discard the bottom.

4. Cut a 1-inch vertical slit in one edge of the dismembered body of the second bottle.

5. Now lengthen the barrel of your trap by grafting this onto the bottomless first bottle. (Note the two-toned example in the photo.) Finesse the slitted end into the opening where the first bottle's bottom used to be, and wedge it tight and straight. You should get an overlap of about three quarters of an inch.

6. Invert the second bottle's cut-off top in the open end of the trap to form a funnel-shaped head, as shown in the photos. Remember to take the cap off first! (Autobiographical.)


7. Fasten the pieces together. The easiest and most elegant way to do this is with a pencil-tipped solder iron. Heat it up well and push the tip gently through the plastic, all along both seams. Don't rush; savour the sizzle. This typically rivets the pieces together even as it perforates them.

If you haven't got a solder iron, next best thing is a heated welding rod or similar metal, followed by a hole-punch, either for paper or leather. After that is a very sharp drill. In any case, cold holes need to be bound together; use string, twist-ties, brads, or nylon zip ties. (This actually makes a more versatile trap, because you can unmount the head to put in certain baits or remove an overlarge catch.)

You can also use a common desktop stapler on the head; a deep-throated pamphlet stapler will fasten the whole trap.

8. Perforate the trap all over, from about three inches below the head seam to about three inches short of the exhaust funnel shoulder. This helps it sink and drain readily and allows prey to smell the bait. (The upper no-hole zone is so you don't perforate the head funnel; the lower one conserves a pint of water in the exhaust funnel when you haul your trap. This greatly reduces injury to life forms, makes them easier to identify and admire, and facilitates removal.) Again, a solder iron makes the neatest and easiest holes.

To set, make a bridle by tying eight-inch strings to four evenly-spaced holes in the head seam and knotting their free ends together. Then tie a long string to the knot. Drop some bait in the barrel, mind the line, and heave the trap overboard.

If you're fishing from the bank or off a dock, you can tie the line off there; the richest pickings are in that zone, anyway. Away from shore, hang a small buoy, such as a stick, cork, fishing bobber, or small plastic bottle, on the bitter end of the trap line and bend on an external anchor, such as a brick or horseshoe, near the head. All sets must be securely belayed to structure or an anchor at all times, regardless of location.

Leave the set unmolested for several hours; overnight is best. To evacuate the catch, hold the drained trap vertically over the water or collecting bucket and unscrew the exhaust cap.

Good starter baits include bread, cheese, cat food, liver, lunch meat, tuna fish, fish parts, clam necks, cocktail shrimp, and corn. Note: it's all about the bait. One won't catch a cold; another will fill the trap. And when seasons, locations, or depths change, it's back to square one.

Survey traps such as these could serve a limited survival end, by supplying bait, or a few crawdads for food. Or they might catch fry that will tell you what to tie on to hook a real meal. Aside from that they're seriously useful in monitoring the health of a waterway (such as the lake I grew up on, which is now mostly dead from overdevelopment and repeated herbicide attacks). Set out a raft of them, vary the parameters over time, and keep careful records. Such hard data can make the difference in a bid to change local law and policy.

Or… just make some kid's day. Ever seen a four-year-old jump up and down over a sculpin in a bottle trap? If Nintendo only knew, they'd make 'em illegal.

Thumbnail-sized rock bass caught this
summer in one of these traps
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