Arrowroot powder might work. It's very flour-like in it's consistency; mixed with egg it's a pretty good binder.

Edit: It's also tasteless (IMO).

Potato starch seems fine to me. I think it's certainly healthier than nut flours and you already know it works so why not just use it?

When I make crab cakes I use crushed up pork rinds in place of bread crumbs and that tastes great.

I made these with coconut flour and egg as a binder. The rest was canned tuna, salmon, & sardine, coconut milk, herbs/spices, and, of course, habanero peppers...

(full recipe here)

Have you tried just omitting the binder? I make Sarah Fragoso's salmon cakes, which is a very similar recipe, but there's no binder (except eggs, I guess). The key is to form patties with your hands, place in heated oil in frying pan, then DON'T mess with it for a full 3 minutes before flipping. Tasty goodness.

Coconut and nut flours don't have the starch that makes for a good binder. If you can eat oatmeal, ground finely it makes a great binder. If you want to be lower carb, extra egg yolks work well, as well as adding flax or chia seeds which thicken.

I think coconut products would taste fine. Try coconut flour or flakes.

I used some LSA Mix - Linseed, Sunflower Kernel and Almond Mix. Gives a different texture to the patties as well :) All very paleo friendly. I aslo added a tin of sardines to mine to get some more Omega 3's my system!!!

Per each 3 oz tin of tuna, I use 1 tbs of coconut flour and one egg, so according to the recipe you linked, 2 tbs should suffice nicely. It does have a hint of coconut sweetness, but I think it complements the flavor of the fish, rather than detracting from it. :)

I like ground flax seeds (meal) in my crab and fish cakes. 2 tbsp per batch is usually enough. If you want a crisp coating try coconut flour.

I make salmon patties and use leftover mashed potatoes as the binder. Or. I don't use a binder at all (although the onion and celery are more likely to fall out during cooking without one).

I put a bit of salmon in the food processor with a couple of tablespoons of mayo or mustard, and blend that into a paste. Then I add the rest of the salmon, though it gets cut into pieces instead of turned into paste. It's the paste that binds it all together, or so the recipe book said.

Got this idea from one of Mark Sisson's cookbooks.

I use potato.It is a very nutritious food - far from just empty calories

"Potatoes are rich in several micronutrients, especially vitamin C - eaten with its skin, a single mediumsized potato of 150 g provides nearly half the daily adult requirement (100 mg). The potato is a moderate source of iron, and its high vitamin C content promotes iron absorption. It is a good source of vitamins B1, B3 and B6 and minerals such as potassium, phosphorus and magnesium, and contains folate, pantothenic acid and riboflavin. Potatoes also contain dietary antioxidants, which may play a part in preventing diseases related to ageing, and dietary fibre, which benefits health."

It doesn't have the omega 6 content of nut flours. I have tried coconut flour but it didn't appeal to me. So - potato all the way!

...nutritional yeast would be my first choice as a replacement. The taste (almost cheese-like) goes great with salmon (or any fish for that matter).

Lots of good ideas. I've been frying a lot of clams, which need breading of some kind for a fast hot sear. I usually use buckwheat meal, but after reading all this I might try some almond flour and see what happens.

We usually grind our own almond meal in the food processor until it's fine, but not flour consistency, then add spices. Works great as a binder!

I tried out blended plantains in a shrimp cake recipe, and they turned out amazing. http://paleograd.blogspot.com/2011/05/bacon-wrapped-shrimp-cakes.html I'm sure it's pretty similar to using mashed potatoes, but plantains get really nice a spongy/fluffy when you fry them--very delicious.