Because they could catch few or no fish, by which trade they got their living; which also was a great plague to the people, whose common diet this was, because out of superstitious conceits they killed and eat but few living creatures, as appears both from sacred and profane writers.
Related Commentaries of Isaiah 19:8
Isaiah 19:8
8 The fishers also shall mourn, and all they that cast angle into the brooks shall lament, and they that spread nets upon the waters shall languish.