The biggest detrimental effect of salmon farming, that is, raising salmon for commercial use rather than turning fingelings loose in rivers, is that man is involved in the process. However, consider the alternative.
Salmon is one of the most sought after and healthy to eat fish. Every year, tens of thousands of pounds of salmon are caught for human consumption. For a very long time, this number has been increasing, until the numbers of native salmon have been negatively impacted and have been dropping. Here in Oregon, as with many states with native salmon runs, the numbers are now watched closely, and the number of fish caught are very closely monitored, year to year. This helps, and our own stock of salmon is slowly increasing, allowing for natural flux. But the US is far from the only nation that harvests salmon. On top of that, not all states with a salmon population, have a management system in place that is designed to make sure that they will continue to be a resource.
All of this means that by using traditional methods of fishing, monitoring, and even using fisheries, the amount of salmon will continue to dwindle until these species are either gone entirely, or so rare as to be uncatchable.
Enter the idea of fish farming. In Southern Oregon, there is a privately owned salmon farm. In four years, that farm can produce salmon that are larger and meatier, yet just as healthy, as naturally caught salmon. This is done by feeding them higher protein foods, and raising them in places where the normal predators are absent. The “waste” products of this farming are the energy used (which a similar sized agricultural farm would also use). The water is natural, and it is filtered before allowing it to re-enter the water table, not that this is necessary since salmon are totally natural. For every thousand pounds of salmon produced, at less cost than it would take to get the same amount by traditional methods, that is a thousand pounds less salmon that need to be caught by commercial operations. While many owners of salmon boats may not like the idea, it creates the potential for ensuring that salmon will continue to thrive. As expensive as it might be, a salmon trawler can be refitted for catching other bountiful fish. It just requires change.
It also must be pointed out that salmon sports fishermen do not make a significant impact on salmon numbers. Fishing with one line, and with a daily limit of fish that can be caught, it much different than using vast nets that capture huge quantities of salmon, and any other creature that happens to be within range of the nets. The cost that this results in is very great, and must be taken into the equation when considering detrimental effects.
By farming the salmon, fewer salmon must be caught commercially, without impacting sports fishermen in any way. People can continue to get the health benefits from the salmon, their palates can continue to be satisfied, and at the same time, the wild stocks of this valuable fish do not have to be diminished. Do the benefits outweigh the detrimental effects? Not only would the answer be yes, it could be easily pushed further. The detrimental effects of NOT farming salmon far outweigh the potential benefits of doing so.