Catfish are bottom dwellers, similar to lobsters, so you'll want to avoid any that have a particular ammonium funk about them, as that can be a sign of spoilage. You can always ask the fishmonger to smell the fillets before he wraps them up, too. Here, catfish fillets are breaded in the classic manner: First they are coated in flour, then dipped in eggs, and finally dredged in seasoned breadcrumbs before being fried to a golden-brown crust.