Hello.

I have always seen crayfish run away when I walk around the pond at night with my spot.

Have you ever tried this.

http://repository.seafdec.org/bitst...ht%20trap.pdf?sequence=1&isAllowed=y

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azteca, I have used glo-sticks in clover traps at night but they are floating traps. Catch loads of YOY crappie. I've never tried one on bottom. When the time comes, I'll do that.

Hello.

I will do a lot of experience this spring with light trap.
I have light trap made with 18 liter water tank , another with big A.B.S pipe, for fish larvae.

I have a bucket that floats with transparent funnels to take the Fairy shrimp an Salamander in my Vernal pool.

I received my glow sticks and also aquarium lights of different color.

I almost finished my On-demand feeder, I also made a long rod with ties to put around 20 worms in it , this long rod will be right above the water with the worms, to try to get the perch out to catch them.

But with the Covid everything is more complicated to do.
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azteca, you have quite the list of interesting experiments/projects lined up. I'm looking forward to your reports.

When I have raised crayfish in tanks of several thousand gallons in capacity, the crayfish where not attracted to the light sources I provided. Rather, they were attracted to the swarms of zooplankton (water fleas mostly) that congregated near the light source. If no zooplankton, then crayfish did not spend additional time around the light source.

Hello.

I am going to do some spot in my pond with different color.

I would like to know which color attracts zooplankton the most, without being too aggressive like white light.

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If water is clear, then green will will attract zooplankton from a greater distance. If the water is turbid, then red is likely to give better penetrance, but will not attract the plankton from as far away as colors on the more green (shorter wavelength) side of spectrum when water is clear.

I have been using black lights (blue colored to UV) to attract flying insects better than other colors, but such light sources penetrate even clear water very poorly. They make the water appear milky close to light source.

Hello.

Once we know that adult fish are more attracted to Zooplancton then to the light itself, we even use the light to fish in some countries.

At this point is it ridiculous to think that some fish could even choose to lay their eggs and make their nests where there would be a non aggressive green light full of zooplankton.

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I've never tried it. That sounds interesting. We need to find out more about this. I usually used ordinary lamps to attract crayfish. My dad often takes me to the shore to catch them. I ordered a couple of times lamps from Chinese sites (Joom, Ali). I don't recommend it; they are too poor quality. Then I tried these from amazon https://www.amazon.com/Night-Light-Plug-Smart-Sensor/dp/B07NF4P12L. It is very simple, but very light and comfortable. I will use them for now, but I think I will think about something more professional over time. Your article seemed very useful to me; I will read it and think about buying it.

Crawfish actually glow bright white/blue when exposed to 365nm light. The light also seems to disorient/daze them, making it very easy to scoop them up with a net. This is the same phenomenon that you will see with scorpions, but it seems to be lesser known. Due to the wavelength, you cannot penetrate into deeper water(12 inches is probably the deepest a good light will penetrate) , but when shore hunting they light up like Christmas lights.

The same is true with ocean crustaceans like blue crabs and sand fleas, walking the beach at night with a 365nm light and it lights up all the hidden organisms like a scene out of avatar.

You can find fairly inexpensive lights on Amazon.

I used a UV light at night to make my fishing line glow & had pretty good success. However, it attracted so many flying insects that bats became a problem! Evidently they can neither see nor echolocate fishing line, would frequently run into it.

Thanks, Dave. Do you think this would work with grass shrimp?

I have proven that the 365nm light won't glow the crayfish in our pond in Ontario Canada. I tried it in the water and out of the water just in case the pond dye stopped the light penetration. Even out of the pond they will not glow with the black light. Too bad I was very excited this would work.

Cheers Don.

I remember old episodes of The Deadliest Catch where a guy was trying to increase attraction to traps with something other than bait. They tried several lights (and other stuff if i remember correctly) but I don't think anything proved to be as good or better than plain old fish.

I think you must have those fancy Canadian "stealth" crayfish!

Dave if you are still watching this thread can you give more information? Certainly you might be exposing a specific type of crayfish? If it is in Michigan is it a rusty crayfish for example? It would seem odd that your crayfish are unique but maybe it is your specific source of the UV light is unique?