I never thought it was a weird claim i always thought it was along the same line as using birds to check for deadly gases,(reply>), Poor canaries :( They're so precious, they didn't deserve that,(reply>), ikr we use animal for century. why using clam can be unbelievable?,(reply>), I had the same experience as Tom: it sounded plausible, as you say, but when I went to find out more about it, the stuff you could find on the internet was all VERY low-quality. Almost all of the articles were either clickbait-y blurbs where the author had obviously not done any kind of research beyond repeating what some other blurb said, or else they were write-ups from more reputable sources, but they were about the documentary rather than the clams. So it was easy to verify that the documentary existed, but I couldn't find anyone who had, for instance, called the water treatment folks to ask them if they really used clams, or whether it was still a thing, or anything like that. And since I hadn't seen the documentary and I don't speak Polish, I couldn't really tell. Maybe the "documentary" was some kind of art project. Maybe the clams were hypothetical or metaphorical. Maybe there's some kind of obvious pun where anyone from Warsaw watching the documentary would understand that it was actually about X and the whole thing with the sensors glued to shells referenced that, but monoglot English clickbait listicle-writers didn't get it.<br><br>So I'm glad to see Tom checking it out, because it is an interesting solution!,(reply>), It's not quite as direct as these clams or canaries but looking at what organisms naturally live in a body of water is an important way to estimate water conditions and commonly used by ecologists.  <br>Like if the only thing in a lake is bloodworms (full of haemoglobin) then the dissolved oxygen levels are probably really low for some reason.,(reply>), @Vez <br>The miners who found a way to get the unconscious bird(s) out safely clearly felt the same. To them, “No-one gets left behind” included the canary.