John Lightfoot on Matthew 14:17

[Two fishes.] What kind of fish they were we do not determine. That they were brought hither by a boy to be sold, together with the five loaves, we may gather from John, chapter 6:9. The Talmudists discourse very much of salt fish. I render the word salt fish, upon the credit of the Aruch: he citing this tradition out of Beracoth, "Do they set before him first something salt, and with it a morsel? He blesseth over the salt meat, and omits [the blessing] over the morsel, because the morsel is, as it were, an appendix to it. The salt meat, saith he, is to be understood of fish, as the tradition teacheth, that he that vows abstinence from salt things is restrained from nothing but from salt fish." Whether these were salt fish, it were a ridiculous matter to attempt to determine; but if they were, the manner of blessing which Christ used is worthy to be compared with that which the tradition now alleged commands.