I'd keep it, but not a big deal.

For タバコ, we decided just to drop the nokanji tag. I think we should do the same here.

@@ -13 +12,0 @@
-<re_nokanji/>

Google N-gram Corpus Counts
╭─ーーーー─┬─────────┬───────╮
│ 柳葉魚　 │   8,263 │  2.6% │
│ ししゃも │ 240,181 │ 77.0% │
│ シシャモ │  63,547 │ 20.4% │
╰─ーーーー─┴─────────┴───────╯
ししゃも・シシャモ is 熟字訓 for 柳葉魚

Kanjipedia, Sankoku

.

Wouldn't we usually have it as 柳葉魚：シシャモ since it's a foreign word used with kanji as 熟字訓?
I mean, I can see that ししゃも is used a lot, and sankoku even gives it as a headword. So it does make sense to have it.
But most kokugos have it as 柳葉魚：シシャモ, as described.

What about having a [nokanji] tag on ししゃも instead? Just out of curiosity
This way we would dissociate ししゃも from the kanji form and have シシャモ be the reading.

It doesn't give an error but I doubt it has been done before, has it?

@@ -5,0 +6 @@
+<ke_inf>&rK;</ke_inf>

nikk: (アイヌsusam)
https://ja.wikipedia.org/wiki/シシャモ#名称
>> シシャモ」という名称は、アイヌ語のsusam（スサム、語源はsusu（スス（シュシュ））＝楊、ham（ハム）＝葉とされる）に由来する。

@@ -17 +17 @@
-<lsource xml:lang="ain">susuhamu</lsource>
+<lsource xml:lang="ain">susam</lsource>