This should be treated with utmost caution without statistical and physical proof.
It's not at all physically implausible that crabs sense some electric or magnetic character in the surrounding water through their antennae or some other organ. Electroreception is known in bees, why not crabs? This could easily be the first evidence of that.
I'm replying, no, there's nothing dubious about it. Which doesn't mean it's accurate. Biology has always prominently featured observation from life, and this is, in general, how the field first starts to suspect that, say, bees can sense electric fields.
Experiments on crabs might and should follow, but your skepticism isn't grounded in anything here.
Yes, exactly, because at least counting the crabs and comparing the count with other clusters of crabs would show whether there 'is something'. Missing accuracy is not my problem, it's missing 'there is something' vs. 'there is nothing'. Without any statistical data, there is nothing to talk about, not in biology either, which is also science.
Skepticism is very important. I challenge them to count crabs on cables and compare with crab counts not on cables, and then make a case. That's all.
This is the follow-up experiment.
https://www.mdpi.com/2077-1312/9/7/776
As usual with modern science journalism, it's necessary to click through and read the actual research paper. Otherwise, one will be totally lost.
As for samatman's concerns, the paper uses standard experimental controls and statistical analysis, as expected.
Transcranial magnetic stimulation uses pulsed magnetic fields produced by a strong electromagnet. It's currently an FDA-approved treatment for depression and a pretty common research tool. The fact that it has (some) biological effect is pretty clear: aim it at motor cortex and you can make someone's finger (leg, etc) twitch!
Transcranial electrical stimulation (tES) is a family of techniques that apply weak electric current to the scalp to affect brain activity. These include tDCS (with Direct Current) and tACS (Alternating Current). While their effectiveness has been debated, my group has collected data demonstrating robust effects on the activity of neurons, even deep in the brain. Check out Figure 1 of this paper: https://www.pnas.org/doi/10.1073/pnas.1815958116 It's not always that simple, and it interacts in complicated ways with ongoing brain activity, but it does do something too.
You can get much strong effects if the electrodes are inserted directly into the brain (or muscle) too but it's not all the case that EMFs are biologically "inert".