I received this question recently and it’s quite a common one I get asked. Very often, fish injure themselves during a fight and they may sustain damage to their fins and scales. Do they repair and do they regrow?
Yes, tails and fins can regrow, but usually, not necessarily to the same length. But unlike hair and nails, the tissues in the fins are living. Scales can regrow, similar to nails, so long as the scale pits are not damaged. I often pluck scales away from ulcerated areas to help healing because the calcified structures may inhibit quick repair. I also pluck scales in preparation for surgery, along the incision site.
There are so many things that can regrow in fish. In fact, researchers are studying the zebrafish on just how they do so. Research has shown that zebrafish can regenerate not only their fins and scales, but also the liver, pancreas, heart and spinal cord! When they understand the mechanisms these fish use to regenerate their organs, the information can be used to try to help human patients.