3 Of whom they, overcome, were deprived

Of > By

4 Of their proud beauty, and the one moiety

moiety > half

5 Transformed to fish, for their bold surquidry;

surquidry > presumption, arrogance

6 But the upper half their hue retained still,

hue > appearance, form

7 And their sweet skill in wonted melody;

wonted > [their] habitual, accustomed