Life bicycle of Salmon

There space five varieties of Pacific salmon discovered on Togiak nationwide Wildlife Refuge. Every Pacific salmon room anadromous. In the well-off ocean setting salmon can flourish rapidly, gaining much more than a lb a month. These salmon mature and return come freshwater in ~ 2 - 8 years.  

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Chinook Salmon(Oncorhynchus tshawytscha) King
Chum Salmon(Oncorhynchus keta) Dog
Coho Salmon(Oncorhynchus kisutch Silver
Pink Salmon(Oncorhynchus gorbuscha) Humpy
Sockeye Salmon(Oncorhynchus nerka) Red


Great Nutrient cycle

As salmon prosper in the ocean environment, castle accumulatemarine nutrients, storing lock in their bodies. Castle then deliver thosenutrients back to their stream that origin once it is their time to spawn, dieand decay. Salmon relax their eggs and milt ago into the freshwater tore-seed the cycle. Eggs that don"t get buried in the gravel come to be immediatelyavailable together food for other fish, birds and also insects. ~ spawning the salmondie, and as lock decay valuable nutrients are released. This nutrientsfertilize the water the feeds the developing salmon, filter-feeding insects,and aquatic and terrestrial plant life. This procedure of salmon accumulatingmarine nutrients and also returning them come freshwater streams has actually been ad toas "the great nutrient cycle."

Natal Spawners

One of the many amazing facts around Pacific salmon is theirability to return to their "natal" or residence stream or lake. Salmon arethought to usage several navigation aids to uncover their method back to where theywere hatched. Scientists believe salmon use a mix of a magneticorientation, celestial orientation, the storage of their home stream"s uniquesmell, and a circadian calendar to go back to their natal stream come spawn. Thememory and smell centers in a salmon"s brain grow rapidly just before it leavesits house stream for the sea. A salmon deserve to detect one fall of water from itshome stream blended up in 250 gallons of sea water. Salmon will follow this faintscent trail, through the help of the other methods discussed above, earlier to theirhome stream to spawn.

High Mortality

Although a solitary female salmon have the right to lay 1,000 to 17,000eggs, very few of those eggs actually survive from fertilization to maturity.An median of 3 fish returning for every parent fish that spawns would beconsidered an excellent production. Many natural and also human-related factors cause thishigh mortality. Throughout spawning eggs might not be fertilized, or might not getburied in the gravel prior to they room either consumed by predators (birds and also fish)or come to be damaged together they bounce along the flow bottom. Part eggs might notmature and also hatch because of freezing, dry out if the water level drops too low,being trapped in the gravel, or gift smothered by silt.

Those egg that successfully hatch to "alevin"stage continue to grow, and also then emerge from the gravel together "fry." Frybecome subjected to a whole brand-new batch the obstacles and also predators, due to the fact that salmonat this phase are near the bottom that the food chain. Pink and chum salmonjuveniles head out to sea immediately. The other species may invest as plenty of astwo year in freshwater prior to they head out to sea. Throughout times the theseseaward movements you deserve to find matching concentrations the predators, suchas beluga whales, arctic terns, gulls, and other fish species.


Salmon reach sexualmaturity in ~ 2 to 8 year old. Different types mature at different rates. Seebelow for info on the spawning of every of the 5 salmon varieties onTogiak Refuge. As soon as the adult salmon are prepared to spawn, after your longjourney homeward, they select spawning sites with water circulation through the gravelwhich will provide oxygen for your eggs and carry far carbon dioxide.

Once a woman salmonselects a spawning site, she quickly pumps she tail to wash out a depression inthe stream gravel. ~ the eggs are laid, the female provides the exact same tailmovements to totally cover the eggs with gravel. This gravel nests in whichthe salmon deposit their eggs are recognized as redds. Over number of days, femalesmay place several much more redds in a line upstream. A solitary spawning Chinook femalecan lay up to 17,000 eggs! 

Chinook: mature after3-8 years; spawn July - august in big gravel and also deep water with a strongcurrent.  Sockeye: mature after 4-5 years; generate in respectable in finegravel (2-7 cm in diameter) ~ above lake shoals or slack water in rivers.  Chum: mature after ~ 3-5 years; spawn late July - August;spawn in gravel 2-3cm+ and also upwelling currents in rivers or part shallow pondsor lakes.  Pink: mature in ~ 2years; generate August - September over coarse gravel and also sand, in riffles withmoderate to quick currents.  Coho: mature at 4 years; spawn late September - December;utilize a wide selection of spawning sites and also currents, regularly in the farthestreaches the drainage.  Egg

Although thousandsare laid, as much as 85% of the eggs deserve to be lost before hatching. The egg hatchafter 6-20 weeks. Hatching times are influenced by water temperature, level ofoxygen and also carbon dioxide, and vary for the different species. 

Chinook: hatchingoccurs at 12 weeks  Sockeye: hatching occurs after 8 to 20 weeks  Chum: hatching occurs after 8 to 16 weeks  Pink: hatching occurs after 8 to 16 weeks  Coho: hatching occurs after 6 to 7 weeks  Alevin

A recently hatchedsalmon is dubbed an alevin. In ~ this stage, the looks favor a thread through eyes andan huge yolk sac. Alevin remain in the redd until the yolk sac is absorbed.At this point, they work-related their method up v the gravel and also become free-swimming,feeding fry. Alevins must have cool, clear, oxygen-rich water come remainhealthy. Too much sediment or too much water temperatures deserve to kill the fish.Aquatic insects and other fish room an alevin"s primary predators.


Salmon fry may go come sea quickly after they hatch or mayspend number of years in freshwater. Most types of salmon fry have actually parr marks(bars and spots follow me their sides) that act together camouflage to assist to avoidpredators and hide amongst the cover listed by rocks, stumps, undercut banksand overhanging vegetation. Parr markings differ for fry of various species. Assalmon fry thrive larger, they move out into an ext open, much faster moving water.During your fresh water residence, fry feed chiefly ~ above terrestrial insects.Fry may form into schools during their freshwater residence. 

Chinook: fry have actually bar-shaped parr marks i beg your pardon are bigger than the spaces between.  Sockeye: fry have short, oval parr marks, prolonging a littlebelow the center of the body; silver- in color, v a tint of blue in theback.  Chum: fry have actually small, distinctive parr marks and slight spotson the body; go to sea practically immediately ~ above emergence and also migrate atnight.  Pink: fry have no parr clues (silvery).  Coho: fry have actually bar-shaped parr marks; rarely have actually spots onupper fifty percent of dorsal fin.  Smolt

Many physiological and also morphological changes occur in ayoung salmon to aid it make the shift from a freshwater come saltwaterexistence. This process is called smoltification. As the moment for migration tothe sea approaches, the salmon acquire the dark back, light belly, and also silverycoloration typical of fish life in open water. They seek deeper water, avoidlight, and their gills and kidneys begin to change so the they can processsalt water. The young fish continue to be in estuaries and tidal creeks feeding onsmall fish, insects, crustaceans and also mollusks. They progressively move right into deeper,saltier water, till they enter the ocean.

Life in the naval Environment

Alaskan salmon can stay in ~ sea for as much as 7 years, althoughthis varies by species. During their s existence, salmon mainly eatfish, invertebrates, and also crustaceans.  

Salmon can undertakeextensive ocean movements of end 3,000 miles, and also average approximately 18miles per day depending upon the species. Generally, juvenile salmon fromsouthwestern Alaska streams move from the Bristol and also Kuskokwim bays throughthe Aleutian Island chain into the northern Pacific Ocean and also the Gulf ofAlaska. Part salmon populations may use the Bering Sea extensively. Motion ofsalmon in the s is believed to be time to take benefit of seasonal foodavailability and ocean conditions.  

Salmon room all brightsilver while in the s environment, however when the lock return tofreshwater come spawn, castle undergo plenty of physiological and also morphological changes.First they should switch from utilizing saltwater come freshwater. Return tofreshwater, they readjust body shade from a silver- to a brown, environment-friendly or reddepending on the species. The males of some types may change their human body shapeand develop a hooked snout, humped back, and elongated teeth, i m sorry are provided toattract a mate and also defend spawning territory. Salmon stop feeding once theyenter freshwater, yet they are able come travel countless miles come spawning grounds byusing the stored energy from their ocean residence. Every adult salmon die afterspawning, and also their body decay, thus offering nutrients to futuregenerations the salmon.

ResourcesMorrow, James E.1980. The freshwater fishes the Alaska. Alaska Northwest publishing Company.Anchorage Alaska.  Groot, C. And L.Margolis (ed.). 1991. Pacific salmon life histories.

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