There is no amount of regulations on the taking of fish that will correct this without protecting the marine environment that the fish need to survive. You can only take what the resource is able to replace. And if you take more or reduce the ability to replace, then you are losing the battle.
And getting back to the original suggestion of Peter's, telling an "old time San Pedrano" that he should stop fishing so divers can see more fish is not the answer.
By reducing the amount of fish taken and protecting them during critical times in their lives, like spawning would increase their numbers, and offset the damage done to the marine environment by over-fishing and over-development of the caye.
Let's face it, no one stops growth in BZ or any other place on the planet that people want to live.
Every resident of Ambergris Caye should pay a fish tax so that fishing and diving are protected
The money could be sent to Belmopan where astute bureaucrats would create a plan and implement policy on how best to save the declining fish population as well as create revenue for a few, to the detriment of the populace and tourist alike