So, we are left with common sense. Here is a partial list of things to consider:
If too many fish (or lobsters or other sea life) are harvested, at first there might not be any sign of harm. Eventually, however, the yield of harvest will decrease and get less and less.
The only way to know whether a fish population is declining is to actually count them. Because many species migrate, you have to do counts at various times of the year. Scuba divers often volunteer to perform such fish counts. Click here to learn how scuba divers conduct the counts.
If you stop fishing, the reefs may become re-populated quickly. As the reef habitat is vacated, the empty niches attract other animals from adjacent areas to move in. There is a risk of extinction of many species. By decreasing the population, you reduce the chances for successful reproduction, and the problem might get so bad that you drive the over fished species into extinction. Think of it like eating seed corn. If you ate all the seed, there would be no way to plant a new crop.
So, the obvious solution is to restrict harvesting - by law if necessary. This is a major effort in all state fish and game agencies. Click here for a listing of state fish and game agencies throughout the U.S.