Hi Paul
It isn't so much that parrot fish numbers are falling per se, more that the larger fish seem less numerous than I remember several years ago.
There used to be some very big fish around the reef at Arnos Vale and these appear to have been replaced by much smaller fish of the same species.
O.K so fish don't live forever and maybe it's pure coincidence, but guys using snorkel gear and powered spear guns have been seen taking serious numbers of parrot fish. I remember seeing around 60 -70 on the fish tables by the Inn on the Bay at Lambeau, which were caught over the reef there.
There is certainly a local market for them and I believe they they are baked whole, packed in sea salt, in many parts of the world where they occur.
Ciguatera does build up in certain species of reef fish that graze on the algae that contains the toxin and the bigger the fish the more likely the risk of poisoning.
As with many toxins, heavy metals and pesticides, the apex predators accumulate high levels in their flesh as they consume the smaller (safer) fish. The Ciguatera neuro-toxin becomes concentrated the further up the food chain you go.
Barracuda are one of those fish that I wouldn't eat, but in many places around the world where Ciguatera occurs, indiginous peoples are rarely affected by it. In fact cuda are a delecacy where ever they are caught, although I can't help but wonder what the long-term affects of eating them could be - man being THE apex predator
Cheers
Steve
Take only photos - leave only footprints. I like that concept.