There are seven different species of Pacific salmon, which belong to the genus Oncorhynchus. Atlantic salmon generally don't live long after spawning but are capable of surviving and spawning again. Most Pacific salmon die shortly after spawning, with the exception of steelhead. Atlantic salmon used to be found from Long Island Sound to New England, but those populations no longer exist in these rivers. Currently U. Atlantic salmon are only found in a handful of rivers in Maine.
Atlantic salmon go to sea to grow. The energy content and abundance of food in the ocean is much higher than in freshwater, so fish are able to grow very big, very quickly. This is important because larger fish are less likely to be eaten and the females have more eggs.
A lot of eggs are needed to produce enough juveniles that will grow to maturity and return to spawn and sustain the population. Young Atlantic salmon called "smolts" migrate to sea every year in the spring. Due to regional climate impacts, the smolt run is starting earlier than in the past. The run begins later at northern latitudes. Atlantic salmon smolt are usually years old when they begin their migration in U.
North American Atlantic salmon migrate in the spring from the rivers where they were born. They move into the Labrador Sea for their first summer, autumn, and winter. The following spring they move to the coastal waters of Labrador and the Canadian Arctic, West Greenland, and sometimes to the waters of East Greenland.
After a second winter at sea, adults from many populations are large and mature enough to spawn, and they migrate back to freshwater areas to reproduce. A landlocked Atlantic salmon is a freshwater form of the sea-run Atlantic salmon. They are genetically considered a subspecies of the sea-run Atlantic salmon.
They reside in lakes, never making the marine migration. They generally do not grow as large as sea-run fish, averaging between 12 and 20 inches long. In fresh water, young salmon mostly eat small insects such as mayflies, stoneflies, caddisflies, blackflies, and riffle beetles.
Sometimes they eat small amphibians and fish. Just before adults migrate to estuaries to begin the spawning migration, they stop eating altogether. In freshwater, juveniles are eaten by a variety of fish smallmouth bass, striped bass, Northern pike, slimy sculpin, etc.
Atlantic salmon are also caught for consumption by humans in targeted aboriginal or traditional First Nations fisheries. If so, are they significantly different? Does it matter? If a hatchery fish spawns with a wild fish, does it dilute the gene pool?
While originally derived from wild populations, years of culturing under artificial conditions have resulted in adaptations and changes to hatchery reared fish. For example, hatchery fish rely on hand-feeding, where wild fish must hunt for food. Hatcheries provide artificial shelter for fish versus the natural shelter found in a stream. Compared to hatchery fish, wild fish are usually more successful at surviving the rigors of the natural environment long enough to reproduce.
Omega-3 fatty acids are found in every kind of fish but are especially high in fish such as salmon that store a lot of oils in their muscles. Omega-3 fatty acids reduce the risk of cardiovascular disease in adults and promote healthy vision and brain development in infants.
The controversy about eating farmed verses wild salmon is complex, and reports available in the media, online, and in scientific publications often seem contradictory. Issues fall into three main categories: environmental concerns, contamination, and omega-3 fatty acid levels in edible portions. The good news is both wild and farmed salmon have low levels of mercury, PCBs, and other contaminants.
The import of Atlantic salmon eggs into the Pacific for farming has raised concern about possible transfer of disease to wild stocks. Restrictions on egg importation, testing of broodstock fish from which eggs are taken, and disinfection are intended to minimize disease. The disease issue is also related to how the fish are raised — high stocking densities can worsen a disease outbreak, or in some cases can be a contributing factor.
The potential escape and unintended introduction of Atlantic salmon from marine net pens into Puget Sound and Pacific Northwest rivers and streams is an environmental concern.
While some juvenile Atlantic salmon have escaped, no known sustained runs have been documented, despite the fact that federal and state agencies attempted to establish Atlantic salmon in the Pacific Northwest for many years until the practice ceased in the s. Another concern is how escaped Atlantic salmon may interact with Pacific salmon. Atlantic and Pacific salmon belong to different genera and don't produce fertile offspring. If self-reproducing Atlantic salmon populations become established in Washington, they may compete with native fish.
Adult and juvenile Atlantic salmon have been found in Pacific Northwest rivers and streams. However, successful reproduction has not been observed in Washington State waters. It isn't known if farm-raised Atlantic salmon compete against wild Pacific species for food or spawning sites. Studies have shown that escaped farmed salmon — in either the Pacific or Northwest Atlantic oceans — have a low survival rate in the wild because they are accustomed to being fed.
Further, Atlantic salmon farmed or wild cannot successfully mate with wild Pacific salmon. Pacific salmon species are not reared in marine net pens in Washington. Pollution fish excrement and uneaten feed occurs regularly under net pens, especially if they are in a low current area. Most pens are located in areas where water currents are high.
Pollution from salmon net pens may affect benthic habitat directly beneath pens, but the effect is temporary and benthic habitats recover during inactive periods.
Sea lice from farmed fish may infect native salmon populations. The sea lice issue is complicated, but regulations in the United States and British Columbia require monthly monitoring of farmed salmon for sea lice and notification of authorities and treatment if sea lice numbers exceed three lice per fish.
Today, most of the salmon available for us to eat is farmed. Early studies reported high levels of PCBs and other contaminants in farmed salmon — higher than in some species of wild salmon, such as pink salmon. Follow-up studies haven't confirmed this and the consensus among scientists and regulators is that farmed salmon and wild salmon are safe foods.
Studies on salmon from these sources have shown low levels of organic contaminants in the fish. Strict rules on contaminant levels in feed ingredients are now in place.
Changes in feed have lowered contaminant levels in these fish.
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