# The fishermen will wail and mourn, and all who cast a hook into the Nile will mourn, and those who spread nets on the waters will waste away

"The fishermen who catch fish with hooks or nets will cry in despair because the fish in the Nile have died" 

# cast

throw

# spread nets on the waters

In order to catch fish, some people toss a net on the water. When fish get caught in it, they pull the net with the fish out of the water.

# will waste away

"will grieve." This weakness probably comes from grief.