Salmon

Salmon are any of several species of euryhaline ray-finned fish from the genera Salmo and Oncorhynchus of the family Salmonidae, native to tributaries of the North Atlantic (Salmo) and North Pacific (Oncorhynchus) basins.

Salmon is a colloquial or common name used for fish in this group.

Other closely related fish in the same family include trout, char, grayling, whitefish, lenok and taimen, all coldwater fish of the subarctic and cooler temperate regions with some sporadic populations in Central Asia.

Salmon hatch in the shallow gravel beds of freshwater headstreams and spend their juvenile years in rivers, lakes and freshwater wetlands.

They the migrate to the ocean as adults and live like sea fish, then return to their freshwater birthplace to reproduce.

Populations of several species are restricted to fresh waters throughout their lives.

It is held that fish return to the exact stream where they themselves hatched to spawn, and tracking studies have shown this to be mostly true.

A portion of a returning salmon run may stray and spawn in different freshwater systems.

Homing behavior has been shown to depend on olfactory memory.

Salmon are important food fish and are intensively farmed in many parts of the world.

They are game fish for recreational fishing, by both freshwater and saltwater anglers.

The seven commercially important species of salmon occur in two genera of the subfamily Salmoninae.

Salmon eggs are laid in freshwater streams typically at high latitudes.

Only 10% of all salmon eggs are estimated to survive to this stage.

The smolt body chemistry changes, allowing them to live in salt water.

While a few species of salmon remain in fresh water throughout their life cycle, the majority are anadromous and migrate to the ocean for maturation.

Smolts spend a portion of their out-migration time in brackish water, where their body chemistry becomes accustomed to osmoregulation in the ocean.

This body chemistry change is hormone-driven, causing physiological adjustments in the function of osmoregulatory organs such as the gills, which leads to large increases in their ability to secrete salt.

Hormones involved in increasing salinity tolerance include insulin-like growth factor I, cortisol, and thyroid hormones, which permits the fish to endure the transition from a freshwater environment to the ocean.

The salmon spend about one to five years in the open ocean, where they gradually become sexually mature.

The adult salmon then return primarily to their natal streams to spawn. Atlantic salmon spend between one and four years at sea.

Salmon undergo changes: They may grow a hump, develop canine-like teeth, or develop a kype a pronounced curvature of the jaws in male salmon, changes from the silvery blue of a fresh-run fish from the sea to a darker color.

Salmon can make long journeys, sometimes moving hundreds of miles upstream against strong currents and rapids to reproduce.

Chinook and sockeye salmon from central Idaho, for example, travel over 1,400 km (900 mi) and climb nearly 2,100 m (7,000 ft) from the Pacific Ocean as they return to spawn.

Condition tends to deteriorate the longer the fish remain in fresh water, and they then deteriorate further after they spawn.

Postspawning mortality is quite high (perhaps as high as 40 to 50%.

The redd may sometimes contain 5,000 eggs covering 2.8 m2 (30 sq ft).

The eggs usually range from orange to red.

One or more males approach the female in her redd, depositing sperm, or milt, over the roe.

The female then covers the eggs by disturbing the gravel at the upstream edge of the depression before moving on to make another redd.

The female may make as many as seven redds before her supply of eggs is exhausted.

Each year, the fish experiences a period of rapid growth, often in summer, and one of slower growth, normally in winter.

Freshwater streams and estuaries provide important habitat for many salmon species.

Mortality of salmon in the early life stages is usually high due to natural predation and human-induced changes in habitat, such as siltation, high water temperatures, low oxygen concentration, loss of stream cover, and reductions in river flow.

Estuaries and wetlands provide areas for the salmon prior to their departure to the open ocean.

Salmon not killed by other means show greatly accelerated deterioration at the end of their lives.

Their bodies rapidly deteriorate right after they spawn as a result of the release of massive amounts of corticosteroids.

The migrations of salmon represent a massive retrograde nutrient transfer, rich in nitrogen, sulfur, carbon and phosphorus, from the ocean to the inland freshwater ecosystems.

Grizzly bears capture salmon and carrying them into adjacent dry land to eat the fish, depositing nutrient-rich urine and feces and partially eaten carcasses.

Beaver ponds can provide critical habitat for juvenile salmon.

Salmon are carnivorous, and need to be fed meals produced from catching other wild forage fish and other marine organisms.

Salmon require large nutritional intakes of protein, and farmed salmon consume more fish than they generate as a final product.

Classified as an oily fish, salmon is considered to be healthy due to the fish’s high protein, high omega-3 fatty acids, and high vitamin D content.

Salmon is also a source of cholesterol, with a range of 23–214 mg/100 g depending on the type of species.

Farmed salmon may contain high levels of dioxins, PCB (polychlorinated biphenyl) levels may be up to eight times higher in farmed salmon than in wild salmon,but still well below levels considered dangerous.

Farmed salmon has a high omega-3 fatty acid content comparable to wild salmon.

Salmon flesh is generally orange to red, although white-fleshed wild salmon with white-black skin colour occurs.

The natural colour of salmon results from carotenoid pigments, largely astaxanthin, but also canthaxanthin, in the flesh.

Wild salmon get these carotenoids from eating krill and other tiny shellfish.

The vast majority of Atlantic salmon available in market around the world are farmed (almost 99%), whereas the majority of Pacific salmon are wild-caught (greater than 80%).

Canned salmon in the U.S. is usually wild Pacific catch.

Lox can refer to either cold-smoked salmon or salmon cured in a brine solution, also called gravlax.

Traditional canned salmon includes some skin and bone which adds calcium.

Skinless and boneless canned salmon is also available.

Salmon contains astaxanthin, an antioxidant that gives the fish its characteristic pink color.

This compound is responsible for the salmon’s distinctive appearance and provides important health benefits.

Salmon has 121 calories, 17g of protein, 5.4g of fat, including those beneficial omega-3 fatty acids and the healthful polyunsaturated and monounsaturated fats, and 37.4mg of sodium. A 3.5-ounce serving contains no fiber, sugar, or carbohydrates, making it an excellent lean protein source.

It has the ability to promote heart health, boost brain function and reduce inflammation.

The astaxanthin in salmon has been shown to reduce inflammation throughout the body, protecting cells from damage and potentially lowering the risk of cancer and diabetes.

Salmon is a good source of many healthy nutrients including Omega-3 fatty acids, protein, potassium, selenium, and vitamin B12.

Additional nutrients include vitamin D, copper, and vitamins A and E, which act as antioxidants.

Salmon is a source of the proteins to build muscles, bone, and cartilage and helps maintain muscle mass and bone density.

The vitamin B12 content of salmon supports nerve function, DNA production, and red blood cell formation.

Salmon is a superfood due to its dense concentration of essential nutrients and proven health benefits for cardiovascular, neurological, and overall health.