That odd, mildly off-putting white substance that you've likely noticed coming out of your fresh-out-the-oven salmon fillets is called albumin. And besides looking a little funny, it's nothing to much worry about.
Ever cracked an egg and noticed a weird, white string strung over the golden yolk? That's a good thing! It's called a chalaza, and there are two of them. They can be found on both sides of the yolk, holding it at the center of the egg.