Recall from the context the fish were brought along by some people for a meal on the mountain side. So they could not have been very large. Probably enough for only one or two people normally.
What was at work here was a demonstration of Jehovah God's power to provide for his people through Jesus. That is why after feeding all those thousands, there was enough leftovers to fill several baskets full. All from what only a few people at most brought with them.
And no, the Bible does not lie at any time. The Bible makes clear, "in order that, through two unchangeable things in which it is impossible for God to lie." (Heb. 6:18)