wasn't enough moisture or egg to hold things together.

Sounds like a nice combo.

for potato cakes, along with chopped scallions and dill.

for moisture control. A little curry or chipotle powder is good too.

(But that's with fresh potatoes)

How did you cook them?

For some more ideas:
https://www.google.com/search?q=salmon+potato+cakes

at med-high.

I love raw shredded/frozen (thawed) potatoes in Latkes/German pancakes...... but it won't cook properly and hold together in a salmon potato pancake.

I like the idea of your recipe..... I would be tempted to add Dijon mustard.

They were yummy good. First thing I thought of was the same thing you mentioned - mashed potatoes as the base.

There are the Latke/German style fried made with shredded potatoes and the pancakes made from left over mashed potatoes.

Sounds good.

Another egg is a good idea. I saw one recipe that put a little flour in.

It just depends on personal preference. Hanukkah is coming up and I am always amazed how different the potato pancakes come out depending who is making them -even using the same ingredients! Like all pancakes, the first ones are often a bit off until you get the hang of frying them.

The problem might be with the amount of oil and the type and temperature. Olive oil is not generally my preference for a fry oil - happier at lower temps same with the butter. They are for saute temps.

Potato pancakes are better at deep fry temps. Maybe try something hotter temp friendly like grapeseed oil and cooking it a little hotter with a bit more oil?

Instead of panko use bread crumbs to bind and flour to coat. Don't use butter to fry anything. Use safflower, canola oil or crisco.

Just after I wrote that a TV report came on that the govt plans on banning all transfats. LOL Should have happened a long time ago; lots of places have cut out the hydrogenated fats already. The problem with butter is that it browns and burns too fast for frying. I try to use olive oil often but sometimes the taste seems kinda strong. For baking I use the canola spray.

oil for lower temperature frying and sauteing.

You don't want something like a hamburger patty. I make fish cakes using whatever flake-able type fish I can find like crab or tuna. They always are quite loose and don't bind together well. That's how you know you did it right. What you want is for them to hold together well enough for you to flip them in the saute pan and plate them and even at that you have to be very careful.

line between a flippable pattie that's still loose, and hashbrowns.

I really don't like to add a lot of ingredients. Basically all I do is flake the meat in a bowl (make sure it's well drained), add some prepared Dijon mustard and a some mayo, a bit of seasoning, along with a couple of tablespoons of panko bread crumbs and mix. Then I form each cake with my hands, press each side into a plate of more panko break crumbs, and then put them directly into an oiled hot saute pan and brown each side for about 3 minutes. I use just enough mayo to hold everything together long enough to make it to the plate.

Might I ask what kind of oil you use to saute?

For seasoning I use just a bit of salt and pepper and occassionally I'll throw in a bit of old bay. I also usually throw in some chopped fresh herbs if I have some on hand. I like dill for salmon or tuna and parsley for crab.

Light olive oil is what I generally saute with for most everything although every now and then I'll use clarified butter. When I think it's done I check the internal temperature with an instant read thermometer. It should be about 160F or so. I keep EVOO and light olive oil on hand at all times. I use EVOO for much of my lower temperature cooking and salads. I use light olive oil for higher temperature cooking and for things in which I don't want the stronger taste of EVOO. If you want to go lighter you can broil them, which works fine especially if you're making a lot of them.

You don't have to use a knucklebuster grater on them, a plastic mandoline usually has a shredding blade and won't break the bank. Just use the guard unless you want potato cakes a la thumb.

The fresh potatoes will have a great deal of surface starch which will help to hold the whole thing together.

It won't be a solid cake like the supermarkets carry in the frozen section. There will be bits of potato sticking out all over the place, getting brown and crisp.

If I have leftover fish from dinner, the next night I flake it and mix it with a bit of mashed potato, an egg, and maybe some chopped green onion or parsley. Then I make it into patties, bread in panko, and fry.

Canned salmon at our house usually becomes salmon cakes--mix with egg, bread crumbs, parsley, and onion, make into patties and fry.