Fish cuts exist with mods<snip>
Well, then, it becomes a different gameworld with different rules. I do not know about that mod/its rules/its impact on dog feeding etc.
If you put the mod name someone with that mod can help you maybe. Alternatively you could post under mod's thread if there is one here (or on Steam forums/elsewhere).
<snip>As far as I understand trout and salmon are some of the best nutrionally, but pike are bigger?
On the same official wiki, on the Pike page, we see the following (emphasis mine):
Pikes are a type of large fish. They are one of the more common types of large fish and weigh around 5 -7 lbs. You get them by active fishing with an angling rod in a lake. Pikes do not fill as much hunger as a trout or salmon; nevertheless, they are an important source of food. Roasting them on a fire luckily doesn't require any devices like a cooking pot or pan.
Salmon is best, trout is second best I believe; (as mentioned on the wiki) pike is not bad either (based on size values of each fish, may or may not be the biggest but definitely not the most nutritious).
When going for maximum bang for buck (when drying/smoking/salting fish) using Salmon exclusively could be a good idea but it of course depends on many other factors whether you have adequate fishing-net network to provide that much Salmon before the first (untreated) Salmon-batch goes bad, combined with your ability to use rest of fish in a meaningful way (feeding dogs/selling fresh quickly/treating to sell -rather than keep in your stocks- etc.).
One other thing to consider is the tying equipment update. I do not know if you played in that era but tying equipment were much more valuable in some past versions (hence its permanent impact in my psyche and my nickname) so in earlier versions especially in the early days of a character, for each piece of string consumed in food treatment, you wanted to get max calories.
In contrast, these days you can relatively quick and easily convert year-round-available saplings to tying equipment which then can be used in food treatment (smoking/drying etc.) therefore at least for me, big fish sub-type does not matter that much anymore (pike/trout/salmon); I just treat them all and push to the cellar network as there is a mountain of tying equipment now.
Edit: Typo