Ok, Ive asked the boffins down in the lab and they say
Quote "Its called "Lordosis" and basically a forward (Downward in fish) curvature of the spine. Morwong, Drummer, bream etc have all been caught in this condition.The spline and Ptergiophores (Bones at the base of the dorsal fin) are intact and fully formed"
I had to ask as I'm not that clever but did know in most cases not a injury.
Thanks Boffins.