What's That White Gook When I Cook Fish?

Dear Matthew Alice:

What is that white gook that rises to the surface when you cook fish?

-- Elaine Boyd, the net

Ewwww. Grandma Alice says the white gook is melted collagen, perhaps a little albumin and other proteins. It's stuff the fish used to need to help keep its muscles hooked to its skin and bones. But now it doesn't need the white gook, and I guess we don't either.