John Dominic Crossan
While Crossan gives this item a positive historical assessment, he notes [Historical Jesus, 350f] that it is also a prime example of the ambiguity inherent in the traditions associated with Jesus:
Nothing could illustrate more clearly the problem of deciding original materials even within the first stratum. Jesus could use a more or less proverbial or parabolic image that is radical only in its application, namely, that his vision, his message, or his challenge is as obvious, ordinary, or necessary as this or that action. It is as clear as a fisherman choosing the better fish or a harvester choosing the right moment to begin reaping. But the transmission could just as easily interpret common sense as sapiential mystery hidden from the dawn of creation or eschatological secret to be revealed at the imminent eschaton. Jesus, like all the Cynics, would claim that their life was simply the wisdom of common sense open to all with eyes to see and ears to hear.
Flusser [Jesus, 48, 263] accepts this saying as authentic and uses it as evidence that Jesus disagreed with John the Baptist of the latter's "acute eschatology."
Jesus adopted the idea of the intermediary period between the historical past and the end of history. Yet he is the only known thinker who drew from this scheme the logical conclusion that until the final destruction of the wicked, the righteous and the sinner would necessarily coexist. This insight was necessary for him, because he identified the intermediary period with the rabbinical concept of the kingdom of heaven—according to which the coexistence of the wicked and the righteous is indisputable.
The commentary in [The Five Gospels',' 477f] notes that different theological interests in the Matthean and Thomas versions of this saying: Thomas contrasts the single large fish with the many little fish in the sea, while Matthew has more interest in the eschatological judgment.
The commentary also notes the following close parallel from Aesop's fables:
A fisherman drew in the dragnet he had cast <into the sea> only a short time before. As luck would have it, it was filled with all kinds <of fish>. The small fish made for the bottom of the net and escaped through its porous mesh. The large fish were trapped and lay stretched out in the boat.
Samuel T. Lachs
Lachs [Rabbinic Commentary on the New Testament, 229] notes that there are no rabbinic parallels to this saying.
Luedemann [Jesus, 594] dismisses the Thomas verses as inauthentic "since they describe the knowledge of the Gnostic," while accepting the Matthean saying as authentic because of its eschatological focus.
John P. Meier
Meier does not discuss this saying in the first three volumes of [A Marginal Jew], although he uses it as an analogy for the process of sifting the non-canonical writings as possible sources for historical Jesus research before casting them back into the sea as unfit for use!