Trout most definitely does have scales. It is kosher. With Trout, I think the problem is the species. As far as I can tell some of them have scales and some of them don't.
There is no prohibition on mushrooms. I know that "seed bearing" plant is referenced in Genesis and this is the argument I've seen used regarding mushrooms being not ok, but I think that is invalid. If we go by that as our basis for what is acceptable, then exclusively seed bearing plants and clean animals would be allowed. Dirt, salt, and yeast, for example, would be prohibited by that understanding. However, the law itself makes it clear that dirt and salt and yeast are allowed because they are commanded in certain cases. There is no indication that fungi are disallowed or unclean or anything.
Can the word "herbage" (osheb) mean mushrooms as well? The problem is, some mushrooms are poisonous, whereas "herbage" by traditional definition is not.
"osheb" does not have a clear definition I don't think (based upon available resources). It is generally used as vegetation of some sort for food for man and beast, but I don't know that it has that exclusive meaning. I don't know that it couldn't include something poisonous (as what is poisonous to man or animal can vary, some foods for one are poisons to another). Does the word include fungi? I don't know. I don't perceive it as relevant either way.
In Gen 1:11 "herbage" is what God made to sprout, so I am assuming that mushrooms (fungi) were included. At the same time, in other places it says "herbage of the field" in which case this would exclude mushrooms as they do not usually grow in the field.
I know this is not an argument, but lately I was hesitant to eat mushrooms because they tasted funny to me. Particularly marinaded mushrooms. I noticed that marinaded mushrooms produce slime which is not a good sign in my opinion. I've noticed that everything that has slimy, mushy, fatty taste is usually not kosher.
Some mushrooms are poisonous so this also a bad sign. Just because something is not commanded in the Torah does not necessarily makes it clean.
Another example would be pork. Pork is prohibited yet it is not poisonous really. By this logic, just because a mushroom is not poisonous does not mean it is ok to eat. Non-poisonous mushrooms can be just as bad as pork in the long run.
Another thing I know is that fungi (not mushrooms - mold) is considered bad. See Lev 14:33-37
Yeast is a good example. But I think it does not matter because it is explicitly mentioned in the Torah in different capacities so I think yeast can be classified as an explicit exemption.
Concerning mushrooms, I believe they are allowed and there is no command prohibiting them. I think the answer to this question is in the Torah somewhere. Just need to find it as usual. Any thoughts would be appreciated.
Regarding mushrooms, some are poisonous. This is indeed the case. However, there are many fruits and plants that are poisonous as well, sometimes even making people deathly ill, and those are indeed seed-bearing. Now, if one has awareness, they are theoretically easier to differentiate than fungi are, but it is the case regardless. Also, fungi is naturally present in dirt even if it does not immediately form a fruiting body, and dirt is consumed in the jealousy ritual. But do not think that dirt is ok because it is mentioned in the jealousy ritual. I think it is rather an exception. I do not think that Torah implies that dirt is clean and ok to eat. That would not make sense.
I still hold that the actual commandments (Lev 11) have no prohibition on such things, including fungi. The only basis for something that's not an animal becoming unclean involves the presence of a dead unclean animal. Even then, there is no general prohibition on eating something unclean. The general prohibitions are regarding not eating from specific animals that are unclean and not becoming defiled by them.
I still think that dirt is rather an exception. I also checked Numbers 5:17 and it says that it's not just any dirt but the dirt from "the floor of the Tabernacle", meaning this is a "holy dirt" if you will.
There is no indication that something to be eaten in general purpose (i.e., I'm not referring to the tabernacle rituals, etc) can be unclean and therefore should not be eaten aside from the presence of a dead unclean animal. Apart from ritual, there's no indication that anything like certain plants or fungi or minerals or anything of that sort are inherently unclean and prohibited from being eaten.
Salt is another example. Salt is commanded to be used in offerings.
Salt is considered an essential commodity and food related product (not in the text but by society).
Generally it is completely inorganic and unrelated to animals or seed bearing plants. It is either mined or evaporated, yet we eat it.
Same way with baking soda, etc, but that's not commanded to be used.
Where does Genesis allow for minerals to be eaten?
Torah says that we are capable of differentiating between good and evil so I am assuming this applies to things that I have discussed (mushrooms, baking soda, e.t.c) meaning that it's up to us to determine if these things are good or bad. That would be the most logical explanation. But at the same time it would be nice to find something explicit in the Torah to support this.
ALWAYS REMEMBER - YOU ARE WHAT YOU EAT !!!