Prior to 15w43c, fished treasure (enchanted fishing rods or bows) would be 25% damaged (i.e. 75% durability remaining), and fished junk (leather boots and unenchanted fishing rods) would be 10%–90% damaged with a bias towards higher damage values (i.e. 10%–90% durability remaining with a bias towards less remaining).

Since fishing was changed to use loot tables, fished treasure is now 75%–100% damaged (i.e. 0%–25% durability remaining) and fished junk is now 10%–100% damaged (i.e. 0%–90% durability remaining) with no bias.

There doesn't seem to be a way to reproduce the bias with the current loot table set_damage function, but you could at least get closer to the old values.