I have found inch-long round worms in the flesh of Lake Washington sockeyes, and Cedar and Green River steelhead. First noticed them on fillets after refrigerating them overnight. Also, have found them in cooked/smoked fish when flaking it apart. They may migrate into the flesh from the intestine when the fish stops feeding. First time I found these worms, I almost stopped feeding! Now, I just cook the fish thoroughly, don't look too closely at it, and drink lots of wine with the meal