"Everywhere, there are Jews," writes Stuart Schwartz in "Chris Matthews and the Jews" at American Thinker, "They have penetrated the highest ranks of government, control vast swaths of the economy, and bend nations to their demonic will. But not to worry: Chris Matthews is on the case."
Gefilte fish, of course, is not an actual fish. Schwartz's reference to netting gefilte fish, then, is a fun way to mock Matthew's self-righteous ignorance. ("Gefilte fish" a mixture of carp, whitefish, and pike ground up and mixed with other stuff; see a recipe here. It's a sort of fish ball. So to say that someone puts their nets out "when the gefilte fish are running" is as absurd as it would be to say that cowboys herd salamis.)
"Chris Matthews and the Jews" is a must-read piece, written in a delightfully snarky and exceptionally well documented style.