Why does 鱧 not contain the 口 radical?

Question

I was looking up the use of the 豆 radical and I noticed something strange in multiple dictionaries. Of the 60 kanji that use 豆, 59 of them are also said to use 口. The the 1 that does not is 鱧. Numerous other kanji appear to use 豆 in the same way as 鱧, so why is 鱧 an exception?

Answer 1

So I downloaded ftp://ftp.monash.edu/pub/nihongo/kradzip.zip, unpacked it and re-encoded all files using iconv -s -f EUC-JP-MS -t UTF-8 kradfile > kradfile.utf8.txt and so on. Yes, this is a somewhat ancient encoding apparently modified by Microsoft. Gross. When I then search with rg --color ansi --line-number --follow -Pi 并 . for occurrences of 并 I find, among others, these entries:

平 : 干 并
屰 : 一 并 屮
崹 : ｜ 亠 并 冂 冖 山 巾
嵭 : 亠 并 冖 山 方
嵰 : ｜ 丶 ノ 并 山 ヨ
嶒 : ｜ ハ 并 口 山 日
嶟 : 并 寸 山 酉

It would look like 并 has been used to symbolize 䒑 which probably has no JIS code. So that's that.

Now when you look for characters with 豆 then sure enough 鱧 is among them. Furthermore, all characters that have 豆 also have 并 (meaning 䒑) and 口, except for 鱧, which lacks it (and it also appears in only one of the two files with character components):

鱧 : ｜ 魚 田 豆 日 杰
尌 : 并 十 口 士 寸 豆
巇 : 并 匕 卜 厂 口 山 戈 虍 豆
幮 : ｜ 并 冂 十 口 士 寸 巾 广 豆
愷 : 并 口 山 忙 豆
憘 : 并 十 口 士 忙 豆
暟 : 并 口 山 日 曰 豆
暿 : 一 并 十 口 士 日 豆
曀 : 并 冖 口 士 日 豆
梪 : 并 口 木 豆

Mystery solved, it's just a quirk of the kradfile data that Jisho is sourced on which has a few bumps. Observe that in the above, 忙 is yet another surprising replacement character (for 忄 in this case), and you could probably find many more eastereggs if you were to sift through the data.

Answer 2

For accuracy purposes, I'll advise you to ignore whatever you've read from jisho or elsewhere about "radicals". If you wish to use these graphical primitive parts for mnemonics purposes, that's fine, but since they don't really have anything to do with the Japanese language, I would classify such ways of looking at kanji as opinion-based. 「口」 isn't functionally in any of these characters, apart from its appearance as a collection of strokes written in the shape of 「口」.

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「[鱧]{れい}」 (a type of fish) is comprised of semantic 「魚」 (fish) and phonetic 「[豊]{れい}」. It's not a good idea to further try decomposing 「豊」 (and generally not a good idea to decompose characters at more than a surface-level), as the results likely won't have anything to do with the meanings or sounds of 「鱧」 in a direct manner.

「[豊]{れい}」 is part of a phonetic series of characters, but due to some modern changes in the Japanese writing system, the phonetic nature of this kanji is difficult to get a grasp on, and shows up very rarely:

• Japanese uses the shape 「豊」 as a simplification of 「[豐]{ほう}」, but this is non-orthodox, as 「豊」 and 「豐」 originally represented different morphemes;
• 「[豊]{れい}」 is the phonetic component of 「[體]{たい}」 (Shinjitai: 「体」);
• 「[豊]{れい}」 is the phonetic component of 「[禮]{れい}」 (Shinjitai: 「礼」).

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The following would be better asked in separate questions, as they don't actually have anything to do with the meanings and sounds of 「鱧」:

• Why does 「豊」 look like it contains 「豆」?
• Why does 「豆」 look like it contains 「口」?