Do you want a stiff boning blade or more flex?
I have Warthers in S35V, a Buck in S35V, and Fallknivens in VG10.
I like the Warther knives the best, and they are the least expensive.
The Warther blades in S35V hold an edge better than VG10 when cutting through bone, and are
more flexible. I use a 6” Warther in the kitchen all year round.
You can get fishing knives in S35V from a number of makers, and I doubt you
Could tell performance apart between S35V as compared with S30V. Buck makes
Fishing knives in a number of steels including S35V, S30V, and less wear resistant
stainless. If you want something like CPM154 you may need to go custom,
but I doubt it will hold any advantages over S35V.
If you want a long blade for big fish, North Arms in Canada makes them in S35V. I have one of their bird and trouts that I use as a paring knife in the kitchen. The blade is fine, but be aware that they grind the edge so thin that you should take the time to sharpen a secondary bevel before taking it out fishing. Otherwise, you are likely to get chipping. If I didn’t already have good fishing blades, and wanted a longer blade than 6” or 7” I would consider one of theirs.
None of the knives I mention here run much over $100, and many are a bit less.