Quote:
Originally Posted by quack quack
It is all good chatting.
.People blamed the commercial fisherman for the decline in Striped bass up north.Then after all the finger pointing at comm guys it was proved that all 14 of the rivers they spawned in were so badly polluted that the scientist were shocked any new bass ever spawned.This is the truth and it applies to more then Striped bass thats for sure.Once those rivers were cleaned up bass numbers increased rapidly.The only overfishing of Stripers came from bad management.They let guys net the in the mouths of the spawning rivers  |
Actually the decline in stripers was mostly due to overfishing and poor management, not pollution. As soon as commercial fishing was halted for stripers, the population bounced back enormously and now stripers are everywhere.
Pollution and habitat destruction are huge threats to fisheries, but not all fisheries. They have a much more substantial effect on freshwater, inshore species (snook, tarpon, redfish etc) and species that spend a part of their life cycle inshore (grouper, snapper, etc). Even in some of those species which are valuable commercially, such as redfish, overfishing is a larger factor in their declines than pollution (blackened redfish in the Gulf).
Pollution and habitat destruction have much less of an effect on pelagics such as swordfish, marlin, tunas etc that do not rely heavily on inshore habitat during their life cycle. Overfishing is the reason for the declines in pelagics. Overfishing is the cause for the declines in the bottom fisheries off New England (cod, haddock etc). Capt Juan is right, FOR THE MOST PART, the major cause for declines in most fisheries IS overfishing and a constantly growing world population in need of a source of protein.
Now to the issue of mercury. While mercury has always been present, it is increasing due to pollution. Mercury is not coming from "used batteries" on the bottom. Mercury itself is not the entire problem, it is when it is methylated and becomes methylmercury that it finds its way into the food chain and becomes toxic. Here is what happens:
Mercury from incinerators and other pollution gets into the atmosphere and ends up raining down into shallow waters. The mercury is methylated by bacteria and becomes methylmercury. Small fish ingest the methyl mercury, which in turn are eaten by larger fish and so on. The methylmercury bioaccumulates in the larger fish eating predators.
The issues of overfishing and pollution/habitat destruction are intertwined and are very complex. You cannot make the general statement such as "Most of the decline in fish stocks around the world have a direct relation to pollution (Quack Quack)." It is way too general and neglects important factors in an extremely complex issue. While the above statement may be true for a certain species in one area, it may not be true for the same species in another part of its range. Even if it is true for a single species, it almost certainly is not for others. Overfishing will definately have an effect on commercially valuable species, but pollution may be a bigger issue with species not targeted commercially. In fact, when talking about fisheries you are typically talking about species that have commercial value, not those that don't.