What is the meaning of "v'Anu"?
Rashi: It is an expression of Oni and mourning. Radak - this is like "Sa'aniyah va'Aniyah" (29:2).
Who are "ha'Dayagim"?
Rashi: They are the Egyptians, who trap fish from the Nile 1 , which spreads into many Ye'orim made on its banks in all of Egypt, unlike all rivers.
Radak: They are fish trappers. There are two ways to trap fish. (a) One casts a Chikah, which is like a needle bent at the end. It enters the fish's mouth, and they are pulled via it. (b) One spreads a net and fish are trapped in it.
Malbim: They are people whose sustenance is from trapping fish. They mourn, for they lack food.
Malbim: This was sustenance for Egypt; it ceased.
What is "Chikah"?
Rashi: It is a fish-hook. Malbim - it catches big fish, one at a time; also they will die.
Why does it mention "Poresei Michmores"?
Malbim: Even when there are few fish, and one does not catch via a hook, one surely catches some via a net. However, even a net will not help, for all will die.