I have noticed one or two of my tilapia have developed the facial characteristics of Walter Matthau, jowls. I would see one from time to time, probably starting about 5 months after the first stocking, but,I had never caught one until today then I caught two in a row. Both seemed fine, good color and conformation except for the jowls. Does anyone have any idea what might cause this defect? I should have taken a picture but both were cooked almost as soon as they were netted.