Whenever I saute kale there is a fishy flavor. How can I avoid this?

Kale shouldn't taste fishy. It is now because of hippy dippy junk science. They are doing hydroponics w fish. The fish feed the food & the food feed the fish. Dirt isn't being used anymore. It's digusting.
Grow a garden. You can start w pots in your home.

I have experienced this same thing. It doesn't matter what oil I cook it in either. Is this an enzyme thing? Like when people don't like cilantro because it tastes like soap? I'm allergic to most cucurbits and they all have a fishy flavor to me.

I love to eat kale raw, in salads. But if I am going to cook it, I do so very quickly, so that they stay nice and bright and crisp. I find that the more you cook vegetables, the more you alter their flavor, sometimes in a not-so-tasty way.

Here is one of my recipes featuring kale.
http://www.food52.com/recipes/1066_mustardcrusted_tofu_with_kale_and_sweet_potato

This is from a while ago. Now, I would never cook the kale 12 minutes! More like 4.

I cook kale twice. I stem it, rough-chop it, add it to simmering water or broth and cook it until it is almost as done as I like. I'm from the South and we tend to like greens like kale and collards more rather than less done. Then I drain them, chop a little more if I feel like it, and let them sit until they have dried a bit. Then I saute garlic and/or finely minced onion and/or crushed red pepper, add the kale and a little more stock, cover and simmer 5 minutes. This procedure makes kale easy to do ahead and then rewarm, too.

My experience matches prettyPeas re. canola oil and I love her recipe. The other ingredient that brightens up kale is a splash of vinegar or lemon juice before you serve it.

Are you using canola oil? I find that canola oil at high heat releases a fishy smell--I'm not sure why it would be kale-specific, however. My favorite sauteed kale involves sauteeing onions, then adding plenty of garlic, ginger, and red pepper flakes, then kale and maybe some vinegar. I usually use olive oil or grapeseed oil. If there is a fishy taste you are getting from the kale the ginger/garlic/vinegar should complement or mask it.

Maybe start by a saute with slivered garlic, but add some chicken stock to partly braise it, chicken stock will tame bitterness in greens.

Are you using the same pan you use to fry fish in? My kale doesn't smell fishy.