And they say unto him, We have here but five loaves, and two fishes.
He saith unto them, How many loaves have ye? go and see. And when they knew, they say, Five, and two fishes.
But he said unto them, Give ye them to eat. And they said, We have no more but five loaves and two fishes
There is a lad here, which hath five barley loaves, and two small fishes: but what are they among so many?
What I find weird is the translation of this passage in John:
And the other disciples came in a little ship; (for they were not far from land, but as it were two hundred cubits,) dragging the net with fishes.
As soon then as they were come to land, they saw a fire of coals there, and fish laid thereon, and bread.
Jesus saith unto them, Bring of the fish which ye have now caught.
Simon Peter went up, and drew the net to land full of great fishes, an hundred and fifty and three: and for all there were so many, yet was not the net broken.
Note the variation between "fish" and "fishes", both plural. "Fish" is used in its plural sense when the Greek word "opsarion" is used (singular in v9, plural in v10) - this word simply denotes food eaten with bread, which was usually fish. Thus, since the word refers to a type of food rather than "fish" itself, I understand the difficulty in translation - even though the context is clear that there was more than one fish. What puzzles me is that in Jn 6:9, 11 the same word in translated "fishes". In v8 and v11, "ichthys" is used, both times in the plural - this word simply means "fish".
I have used the 1789 revision of the KJV, but the original 1611 edition has the same usage of "fish" and "fishes" in the verses I have dealt with. Likewise, the Tyndale Bible, on which the KJV is largely based, uses "fish" and "fishes" in the same verses (well, technically it uses "fysshe" and "fysshes").
I doubt that Tyndale had predetermined to consistently translate "fish" a certain way - he was but one man, and could not consider every aspect of translation (though he still managed to produce an excellent translation which has directly or indirectly influenced almost all translations today). The KJV committee for translating the gospels may have overlooked this, or, noticing the inconsistent use of "fish" vs. "fishes", chosen to let it be and focus on more important issues. Though the use of "fish" and "fishes" in the KJV is interesting to consider, the usage does not reveal any additional grammatical or theological truth.