- Lack of Vitamin C - this shows up especially in hatchery raised fish but could happen to wild fish, too, if they have a very poor diet
- Injury when young - an injury to the backbone of a young fish could cause them to grow with a curved or deformed spine if the injury is not too severe.
- Birth defects - much like people, fish can hatch from the egg with a defect in the spine that causes the curved spine. If it is geneteic, it can be passed on to their offspring.
- Severe changes in temperature while in the egg - if there are severe water temperature changes after the eggs are laid it can cause this deformity. This happens more often in hatchery raised fish but can happen in the wild.
- Parasites - there is some evidence parasites are cauging deformities in young northern pike in an Oregon study of the Newberg Pool of the Willamette River
Fish with this deformity are safe to eat. I ate the filets from the bass in the pictures with this article. You can see the fish after I caught him and the pictures of his spine after he was fileted.
Back in the 1970s some claimed acid rain caused this deformity. No doubt some will now claim global warming is causing it, but that does not fit in any causes defined by biologists so far.
The Tennessee Wildlife Resources Division has some information on this with more pictures, including one from my site. They show a walleye with the curved spine as well as two different bass picturs. This page has several interesting questions answered.
If you have pictures of deformed fish, send them to me to post here. Also send any information you have about fish deformities.