Fish identifiers! I need your help! What is this thing???

A trip to Oakbank Pond Park revealed a large dead fish, caught in the reeds. It was 2-2.5 feet long and was grey-green in colour with no noticeable patterning. Its pectoral fin had been eaten away, but its dorsal fin, positioned closer to the tail, remained.

Photo 1 is of the entirety of the fish, its gills can be seen toward the left of the photo.

Photo 2 is of the head (top) and tail (bottom). The strangest thing about the fish were the repeating structures lining the sides of the body. What are they? Could they be caused by decomposition?

The head seemed to still be attached to the body. I believe I saw its empty eye socket. The head appears to be long and sloped.

Photo 3 is of the caudal fin. Looks pretty square and relatively small. It doesn't concave either.

Photo 4 offers a closer view of the gills and pectoral fin.

Photo 5 is of the whole fish again. The wind had blown it out of the reeds and closer to the observation deck. Its smell followed.

I've only ever seen Amur Carp in this pond. This fish seemed larger though. Any ideas?