鮭はらす	1,106		
鮭ハラス	6,004

I think we should make it explicit that it's always fish.
I don't think "fatty" is needed.

@@ -5 +5 @@
-<reb>はらす</reb>
+<reb>ハラス</reb>
@@ -8 +8 @@
-<reb>ハラス</reb>
+<reb>はらす</reb>
@@ -13 +13 @@
-<gloss>fatty belly meat (esp. salmon)</gloss>
+<gloss>belly meat (from a fish, esp. salmon)</gloss>

GG5: "〔サケの腹肉〕 belly meat (from a salmon)."
はらす	39515	51.6%
ハラス	37052	48.4%

Yes, include the katakana.

@@ -6,0 +7,3 @@
+<r_ele>
+<reb>ハラス</reb>
+</r_ele>
@@ -10 +13 @@
-<gloss>fatty belly meat (of a fish, esp. salmon)</gloss>
+<gloss>fatty belly meat (esp. salmon)</gloss>

sankoku: はらす「ハラス」さかなの腹がわの、あぶらののった肉。ハラミ。はらんぼ。サケのはらす焼き

ハラスとは？特徴や鮭ハラスについてご紹介
https://delishkitchen.tv/articles/800
一般的に「ハラス」というと、鮭のハラスをイメージする場合が多いでしょう。
...ハラスといえば鮭と広く知られていますが、実はハラスとはお腹の部分を表す言葉で、魚の部位のひとつを指します。

https://gurunavi.com/en/japanfoodie/2017/09/types-of-salmon-sushi.html?__ngt__=TT1470d1bb6001ac1e4a5b9cyrOXnlST8TDXZ_QLSmJbu2
Salmon harasu (belly) is the counterpart to tuna’s toro, or the fatty cut from the belly of the fish. Salmon belly is incredibly rich and also an uncommon menu item, so you’re more likely to find it in a proper sushi restaurant rather than a kaiten-zushi shop. 

https://www.byfood.com/blog/culture/types-of-sushi-fish-beginners-guide
Pacific bluefin tuna - akami, chutoro, otoro, negitoro
Atlantic salmon - sāmon and harasu <<<<<-------
Salmon roe - ikura
...
Items made of salmon meat include simply “salmon” and the fattier salmon “harasu” (salmon belly)—basically the salmon equivalent of otoro.

https://japan-word.com/harasu
Explicit salmon ngrams:
鮭ハラス	6004	49.0%
鮭のハラス	4179	34.1%
鮭のはらす	634	5.2%
鮭はらす	1106	9.0%
サケハラス	137	1.1%
サケのハラス	161	1.3%
サケのはらす	41	0.3%

Tuna harasu? Not really
鮪はらす	48
鮪ハラス	78
鮪のハラス	45
鮪はらす	48
まぐろはらす	0
まぐろハラス	158
まぐろのハラス	83

Was hiragana when I saw it, but katakana seems also common. (in sankoku). I've forgotten if/where that should be included when there are NO kanji. 

Saw this at dinner today at a 回転寿司, as: 大切り焼きはらす (note: no fish identified, I suspect a salmon default). 
Here is the exact dish(with pic.).  Google completely mistranslates as "scallops"?
https://twitter.com/mutenkurasushi/status/1663092818963836929

Sankoku specifically lists harami in the definition.  The delishkitchen entry specifically identifies harasu and harami and as differing because the former is boneless and the latter may have bones.
鮭ハラスの場合、鮭ハラミとの違いは骨があるかどうかです。(delishkitchen)
鮭ハラミは骨がある部分、鮭ハラスは骨がない部分を指します。

jmdictdb's gloss for ハラミ「２」 is: belly meat (e.g. salmon);

However, sankoku specifically says "fish", (and the example is also 'salmon'/サケ はらす焼き, which is the same dish I encountered), and numerous other references seem to indicate that はらす invokes fish specifically (unlike ハラミ which can be a mammal, or whatever), and usually (but not always) salmon. Usually *not* tuna, which has its own terminology.(とろ: fatty cut (esp. of tuna belly))

Search "harasu" in English, and it's endless salmon entries.

Every reference mentions "fattyness".  We list "fatty" with とろ.  sankoku specifically says あぶらののった. fattiness seems to be a key component.