Overfishing Effects More Than Just the Ocean

Salmon migrate yearly from the open Pacific Ocean to the coastal areas of the Pacific Northwest in order to spend about 5-6 weeks reproducing. During this time bears also migrate to these coastal areas to feed on the salmon which is a large part of their diet. This natural interaction has been an important factor of the ecosystem in the Pacific Northwest for many years and now that humans have imposed on this process by overfishing we are seeing changes in the ecosystem itself.

While knowledge of this issue has been around for about 30 years, scientists only began researching it beginning in the early 90’s. According to this research the ongoing problem of overfishing is already beginning to show its effects on the ecosystem, what may happen to the forests and animals of the Pacific Northwest if this issue is not resolved? Through the research of Dr. Tom Reimchen and other scientists, an interaction between salmon and the forests of the Pacific Northwest has been discovered.

Each year black and grizzly bears travel from far away to the streams and rivers in the Pacific Northwest to feed on the salmon that migrate there during their six week spawning period. This causes a local interaction, when the bears catch a fish they take it into the forest so they can eat it and not be disturbed. Usually the bears only eat about half of each fish they catch and leave the rest on the forest floor, which is then consumed by birds, other small animals and insects.

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Through the decomposition of the salmon as well as the bodily wastes of the bears and other animals, the soil in the forest absorbs nutrients as well as nitrogen from the salmon. “The use of stable nitrogen isotopes allows us to identify the relative contribution of salmon to the ecosystem” (Reimchen 2001: 14), this research showed that nitrogen 15, an isotope of nitrogen is present in a large number of the plants in the Pacific Northwest forests.

Nitrogen 15 is mostly found in marine algae and salmon are highly enriched with it so it makes sense that the plants use the remnants of the salmon as a sort of fertilizer to make them grow causing large scale interaction. The presence of the nitrogen in the plants of the Pacific Northwest forests does not mean that the plants necessarily need it to grow. In another experiment performed by Reimchen he sought to answer this question, “I examined yearly growth rings of 13 trees of similar size from sites differing in (salmon) carcass density.

Average growth rate over the last 50 years was 2. 5mm per year within 10m of the stream where carcasses were most abundant and less than 1mm per year where carcasses were not present” (Reimchen 2001: 14). These results are debatable because other factors such as the amount of rainfall and sunlight they get effect plant growth too, but another observation which backs the theory that nitrogen helps the plants grow is that the amount of salmon brought into the forest by the bears each year varies directly with the amount of salmon coming back to the stream each year.

In the conclusion of his research thus far Reimchen believes that if it is not stopped, “... the result of deforestation and overfishing will have ecosystem-level consequences for the remaining forests” (Reimchen 2001: 16). Due to the overfishing of salmon by humans, the migrating salmon population has reduced 80-90 percent in the last 100 years. In nature predators and prey coexist in equilibrium, but with human interference the salmon can not reproduce fast enough to keep up with the amount being caught resulting in a large decrease in their population.

Although there are programs like the MSY or maximum sustainable yield in place which tells fisheries how many fish they are allowed to catch, they do not factor in the natural predators of the salmon and therefore they throw off the balance of the ecosystem. A direct result of over fishing is the harvesting of salmon in fish farms, the salmon are raised in net pens that usually float in areas off the coast. The biggest problem with fish farming is the fish escaping into the wild, for example in 1997, 360,000 salmon escaped from a single farm off the Washington coast. The salmon raised on fish farms are, “... ed concentrated feed and medication to maximize the conversion of feed into growth while minimizing the loss of fish due to disease and escape” (Reimchen 2001: 139), the effects of the salmon raised on farms escaping into the wild may be genetic, ecological, and can cause problems with disease and parasites. The genetic problems the farm salmon can cause are they will interbreed with wild salmon and disrupt their genetic adaptations, replacing their genetic variability and their evolutionary potential. The competition for food, space, and habitat between the farmed and wild salmon could also be a problem.

Farmed fish sometimes get sea lice or ISA a contagious lethal virus that they can pass to the wild salmon. All of these factors are depleting the amount of wild salmon as well as altering the way the salmon live. Another contributing factor to the decline of the salmon population is the political ecology involved. On one side there are the people willing to do anything in their power to protect and restore the status of the salmon in the pacific northwest, but on the other more powerful side are the people who see the salmon as a huge money maker and are doing everything they can to continue overfishing so they can profit from it.

The fisheries not only catch salmon so they can sell it locally, but where they get the most money from is shipping it to large grocery store chains across the country. They must overfish in order to meet the demands of the stores they supply or else the stores will go to another source for salmon, so many fisheries ignore the problem and continue overfishing because they think that if they stop someone else is just going to come in profit off of what they are not catching.

The problem with overfishing and fish farms are not only harming the salmon population, but if nothing is done about these issues it will effect the animals in the pacific northwest as well as the vegetation. Black and Grizzly bears get around 75% of their yearly dietary requirements from the salmon, with the amount of salmon available becoming less and less each year the bears are not going to have enough to eat and their population will decrease as a result.

I also think that with the introduction of the farmed salmon and the diseases they can carry the bears may get sick and die from eating diseased fish. With less bears the vegetation in the pacific northwest will also suffer because less salmon will be transferred into the forests where the plants can absorb the nitrogen and the plants will not grow as much or as quickly, it may also make the plant population less diverse. I believe that the overfishing needs to be controlled by more extreme measures so that the salmon can be allowed to reproduce naturally and keep their population up.

If companies sold salmon raised in a fish farm at lower prices and raised the price of wild salmon this may help as well because the more expensive it is, the less people will buy and the fishing companies will not have to catch as many. Its kind of like how you can go to the store and buy either regular fruit or pay extra for organic, and there is always people who are willing to pay more. I also think that fish farms should not be integrated in the coastal waters, they should be in a completely different location than the wild salmon so there is no chance of them escaping and contaminating the wild salmon.

In addition to the repercussions of fish farming and overfishing on the ecosystems in the Pacific Northwest forests, deforestation is another action by humans that is threatening this area. With the growth rates of the trees already falling due to lack of nitrogen from salmon and humans cutting them down at an alarming rate, it is inevitable that unless serious steps are taken to protect both the salmon and the forest itself from humans the ecosystem in the Pacific Northwest will fail and the forests will be completely destroyed.

References

1)Frissell, C. (1995). Topology of Extinction and Endangerment of Native Fishes in the Pacific Northwest. Conservation Biology, 7. http://www.jstor.org/pss/2386432
2)Reimchen, T. (Fall 2001). Salmon nutrients, nitrogen isotopes, and coastal forests. Ecoforestry.
3)Sachs, J. (15, Jan. 2010). Icon for an Endangered Ecosystem. http:// www.nwf.org/News-and-Magazines/National-Wildlife/Animals/Archives/2010/Icon-for-an-Endangered-Ecosystem.aspx

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