A salmon run is an annual fish migration event where many salmonid species, which are typically hatched in fresh water and live most of their adult life downstream in the ocean, swim back against the stream to the upper reaches of rivers to spawn on the gravel beds of small creeks. After spawning, all species of Pacific salmon and most Atlantic salmon die, [1] and the salmon life cycle starts over again with the new generation of hatchlings.
Salmon are anadromous, spending their juvenile life in rivers or lakes, and then migrating out to sea where they spend adult lives and gain most of their body mass. When they reach sexual maturity, the adults return to the upstream rivers to reproduce. Usually they return with uncanny precision to the natal river where they were born, and even to the very spawning ground of their birth. It is thought that, when they are in the ocean, they use magnetoreception to locate the general position of their natal river, and once close to the river, that they use their sense of smell to home in on the river entrance and even their natal spawning ground.
Trout, which are sister species of salmon, also perform similar migrations, although they mostly move potamodromously between creeks and large freshwater lakes, except for some coastal/estuary subspecies such as steelhead and sea trout that migrate seasonally between salty/brackish and fresh water just like salmon do. There are also landlocked populations of some salmon species that have adapted to spend their entire life in freshwater like trout.
In Northwest America, salmons are keystone species, which means the ecological impact they have on other wildlife is greater than would be expected in relation to their biomass. Most salmon species migrate during the autumn (September through November)[ failed verification ], [2] which coincides with the pre-winter activities of many hibernating animals. The annual salmon run can be a major feeding event for predators such as grizzly bears and bald eagles, as well as an important window period for sport fishermen.
The post-spawning death of salmon also has important ecological consequences, because the significant nutrients in their carcasses, rich in nitrogen, sulfur, carbon and phosphorus, are transferred from the ocean and released to inland aquatic ecosystems, terrestrial animals (such as bears) and the wetlands and riparian woodlands adjacent to the rivers. This has knock-on effects not only for the next generation of salmon, but to every wildlife species living in the riparian zones the salmon reach. [3] The nutrients can also be washed downstream into estuaries where they accumulate and provide significant support for invertebrates and estuarine-breeding waterbirds.
Most salmon are anadromous, a term which comes from the Greek anadromos, meaning "running upward". [4] Anadromous fish grow up mostly in the saltwater in oceans. When they have matured they migrate or "run up" freshwater rivers to spawn in what is called the salmon run. [5]
Anadromous salmon are Northern Hemisphere fish that spend their ocean phase in either the Atlantic Ocean or the Pacific Ocean. They do not thrive in warm water. There is only one species of salmon found in the Atlantic, commonly called the Atlantic salmon. These salmon run up rivers on both sides of the ocean. Seven different species of salmon inhabit the Pacific (see table), and these are collectively referred to as Pacific salmon. Five of these species run up rivers on both sides of the Pacific, but two species are found only on the Asian side. [6] In the early 19th century, Chinook salmon were successfully established in the Southern Hemisphere, far from their native range, in New Zealand rivers. Attempts to establish anadromous salmon elsewhere have not succeeded. [7]
Oceans | Coasts | Species [6] | Maximum | Comment | ||
---|---|---|---|---|---|---|
length | weight | life span | ||||
North Atlantic | Both sides | Atlantic salmon [8] | 150 cm | 46.8 kg | 13 years | |
North Pacific | Both sides | Chinook salmon [9] | 150 cm | 61.4 kg | 9 years | Also established in New Zealand |
Chum salmon [10] | 100 cm | 15.9 kg | 7 years | |||
Coho salmon [11] | 108 cm | 15.2 kg | 5 years | |||
Pink salmon [12] | 76 cm | 6.8 kg | 3 years | |||
Sockeye salmon [13] | 84 cm | 7.7 kg | 8 years | |||
Asian side | Masu salmon [14] | 79 cm | 10.0 kg | |||
Biwa salmon [15] | 44 cm | 1.3 kg |
The life cycle of an anadromous salmon begins and, if it survives the full course of its natural life, usually ends in a gravel bed in the upper reaches of a stream or river. These are the salmon spawning grounds where salmon eggs are deposited, for safety, in the gravel. The salmon spawning grounds are also the salmon nurseries, providing a more protected environment than the ocean usually offers. After 2 to 6 months the eggs hatch into tiny larvae called sac fry or alevin. The alevin have a sac containing the remainder of the yolk, and they stay hidden in the gravel while they feed on the yolk. When the yolk has gone they must find food for themselves, so they leave the protection of the gravel and start feeding on plankton. At this point the baby salmon are called fry. At the end of the summer the fry develop into juvenile fish called parr. Parr feed on small invertebrates and are camouflaged with a pattern of spots and vertical bars. They remain in this stage for up to three years. [16] [17]
As they approach the time when they are ready to migrate out to the sea the parr lose their camouflage bars and undergo a process of physiological changes which allows them to survive the shift from freshwater to saltwater. At this point salmon are called smolt. Smolt spend time in the brackish waters of the river estuary while their body chemistry adjusts their osmoregulation to cope with the higher salt levels they will encounter in the ocean. [18] Smolt also grow the silvery scales which visually confuse ocean predators. When they have matured sufficiently in late spring, and are about 15 to 20 centimetres long, the smolt swim out of the rivers and into the sea. There they spend their first year as a post-smolt. Post-smolt form schools with other post-smolt, and set off to find deep-sea feeding grounds. They then spend up to four more years as adult ocean salmon while their full swimming ability and reproductive capacity develop. [16] [17] [18]
Then, in one of the animal kingdom's more extreme migrations, the salmon return from the saltwater ocean back to a freshwater river to spawn afresh. [19]
After several years wandering huge distances in the ocean, most surviving salmon return to the same natal rivers where they were spawned. Then most of them swim up the rivers until they reach the very spawning ground that was their original birthplace. [20]
There are various theories about how this happens. One theory is that there are geomagnetic and chemical cues which the salmon use to guide them back to their birthplace. The fish may be sensitive to the Earth's magnetic field, which could allow the fish to orient itself in the ocean, so it can navigate back to the estuary of its natal stream. [21]
Salmon have a strong sense of smell. Speculation about whether odours provide homing cues go back to the 19th century. [22] In 1951, Hasler hypothesised that, once in vicinity of the estuary or entrance to its birth river, salmon may use chemical cues which they can smell, and which are unique to their natal stream, as a mechanism to home onto the entrance of the stream. [23] In 1978, Hasler and his students found that the way salmon locate their home rivers with such precision was because they could recognise its characteristic smell. They further demonstrated that the smell of their river becomes imprinted in salmon when they transform into smolts, just before they migrate out to sea. [20] [24] [25] Homecoming salmon can also recognise characteristic smells in tributary streams as they move up the main river. They may also be sensitive to characteristic pheromones given off by juvenile conspecifics. There is evidence that they can "discriminate between two populations of their own species". [20] [26]
The recognition that each river and tributary has its own characteristic smell, and the role this plays as a navigation aid, led to a widespread search for a mechanism or mechanisms that might allow salmon to navigate over long distances in the open ocean. In 1977, Leggett identified, as mechanisms worth investigating, the use of the sun for navigation, and orientation to various possible gradients, such as temperature, salinity or chemicals gradients, or geomagnetic or geoelectric fields. [27] [28]
There is little evidence salmon use clues from the sun for navigation. Migrating salmon have been observed maintaining direction at nighttime and when it is cloudy. Likewise, electronically tagged salmon were observed to maintain direction even when swimming in water much too deep for sunlight to be of use. [29]
In 1973, it was shown that Atlantic salmon have conditioned cardiac responses to electric fields with strengths similar to those found in oceans. "This sensitivity might allow a migrating fish to align itself upstream or downstream in an ocean current in the absence of fixed references." [30] In 1988, researchers found iron, in the form of single domain magnetite, resides in the skulls of sockeye salmon. The quantities present are sufficient for magnetoception. [31]
Tagging studies have shown a small number of fish do not find their natal rivers, but travel instead up other, usually nearby streams or rivers. [32] [33] It is important some salmon stray from their home areas; otherwise new habitats could not be colonized. In 1984, Quinn hypothesized there is a dynamic equilibrium, controlled by genes, between homing and straying. [34] If the spawning grounds have a uniform high quality, then natural selection should favour the descendants that home accurately. If the spawning grounds have a variable quality, then natural selection should favour a mixture of the descendants that stray and the descendants that home accurately. [21] [34]
Prior to the run up the river, the salmon undergo profound physiological changes. Fish swim by contracting longitudinal red muscle and obliquely oriented white muscles. Red muscles are used for sustained activity, such as ocean migrations. White muscles are used for bursts of activity, such as bursts of speed or jumping. [35] As the salmon comes to end of its ocean migration and enters the estuary of its natal river, its energy metabolism is faced with two major challenges: it must supply energy suitable for swimming the river rapids, and it must supply the sperm and eggs required for the reproductive events ahead. The water in the estuary receives the freshwater discharge from the natal river. Relative to ocean water, this has a high chemical load from surface runoff. Researchers in 2009 found evidence that, as the salmon encounter the resulting drop in salinity and increase in olfactory stimulation, two key metabolic changes are triggered: there is a switch from using red muscles for swimming to using white muscles, and there is an increase in the sperm and egg load. "Pheromones at the spawning grounds [trigger] a second shift to further enhance reproductive loading." [36]
The salmon also undergo radical morphological changes as they prepare for the spawning event ahead. All salmon lose the silvery blue they had as ocean fish, and their colour darkens, sometimes with a radical change in hue. Salmon are sexually dimorphic, and the male salmon develop canine-like teeth and their jaws develop a pronounced curve or hook ( kype ). Some species of male salmon grow large humps. [37]
Salmon start the run in peak condition, the culmination of years of development in the ocean. They need high swimming and leaping abilities to battle the rapids and other obstacles the river may present, and they need a full sexual development to ensure a successful spawn at the end of the run. All their energy goes into the physical rigours of the journey and the dramatic morphological transformations they must still complete before they are ready for the spawning events ahead.
The run up the river can be exhausting, sometimes requiring the salmon to battle hundreds of miles upstream against strong currents and rapids. They cease feeding during the run. [5] Chinook and sockeye salmon from central Idaho must travel 900 miles (1,400 km) and climb nearly 7,000 feet (2,100 m) before they are ready to spawn. Salmon deaths that occur on the upriver journey are referred to as en route mortality. [38]
Salmon negotiate waterfalls and rapids by leaping or jumping. They have been recorded making vertical jumps as high as 3.65 metres (12 ft). [39] The height that can be achieved by a salmon depends on the position of the standing wave or hydraulic jump at the base of the fall, as well as how deep the water is. [39]
Fish ladders, or fishways, are specially designed to help salmon and other fish to bypass dams and other man-made obstructions, and continue on to their spawning grounds further upriver. [40] Data suggest that navigation locks have a potential to be operated as vertical slot fishways to provide increased access for a range of biota, including poor swimmers. [41] [ clarification needed ]
Skilled predators, such as bears, bald eagles and fishermen can await the salmon during the run. Normally solitary animals, grizzly bears congregate by streams and rivers when the salmon spawn. [3] [42] Predation from harbor seals, California sea lions, and Steller sea lions can pose a significant threat, even in river ecosystems. [43] [44]
Black bears also fish the salmon. Black bears usually operate during the day, but when it comes to salmon they tend to fish at night. [45] This is partly to avoid competition with the more powerful brown bears, but it is also because they catch more salmon at night. [46] During the day, salmon are very evasive and attuned to visual clues, but at night they focus on their spawning activities, generating acoustic clues the bears tune into. [45] Black bears may also fish for salmon during the night because their black fur is easily spotted by salmon in the daytime. In 2009, researchers compared the foraging success of black bears with the white-coated Kermode bear, a morphed subspecies of the black bear. They found the Kermode bear had no more success catching salmon at night time, but had greater success than the black bears during the day. [47]
Otters are also common predators. In 2011, researchers showed that when otters predate salmon, the salmon can "sniff them out". They demonstrated that once otters have eaten salmon, the remaining salmon could detect and avoid the waters where otter faeces was present. [48] [49]
The term prespawn mortality is used to refer to fish that arrive successfully at the spawning grounds, and then die without spawning. Prespawn mortality is surprisingly variable, with one study observing rates between 3% and 90%. [38] [50] Factors that contribute to these mortalities include high temperatures, [51] [52] high river discharge rates, [53] and parasites and diseases. [50] [54] "At present there are no reliable indicators to predict whether an individual arriving at a spawning area will in fact survive to spawn." [38]
The eggs of a female salmon are called her roe. To lay her roe, the female salmon builds a spawning nest, called a redd, in a riffle with gravel as its streambed. A riffle is a relatively shallow length of stream where the water is turbulent and flows faster. She builds the redd by using her tail (caudal fin) to create a low-pressure zone, lifting gravel to be swept downstream, and excavating a shallow depression. The redd may contain up to 5,000 eggs, each about the size of a pea, covering 30 square feet (2.8 m2). [55] The eggs usually range from orange to red. One or more males will approach the female in her redd, depositing his sperm, or milt, over her eggs. [56] 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 will make as many as seven redds before her supply of eggs is exhausted. [56] [57]
Male pink salmon and some sockeye salmon develop pronounced humps just before they spawn. These humps may have evolved because they confer species advantages. The humps make it less likely the salmon will spawn in the shallow water at margins of the streambed, which tend to dry out during low water flows or freeze in winter. Further, riffles can contain many salmon spawning simultaneously, as in the image on the right. Predators, such as bears, will be more likely to catch the more visually prominent humped males, with their humps projecting above the surface of the water. This may provide a protective buffer for the females. [58]
Dominant male salmon defend their redds by rushing at and chasing intruders. They butt and bite them with the canine-like teeth they developed for the spawning event. The kypes are used to clamp around the base of the tail (caudal peduncle) of an opponent. [58]
The physical condition of the salmon deteriorates the longer they remain in fresh water. Once the salmon have spawned, most of them deteriorate rapidly (a.k.a. "spawned out") and soon die. Some deteriorating salmon are still alive, but their bodies have already begun the process of rotting, [59] and these deteriorating salmon are sometimes colloquially called "zombie fish". [60] This is because upstream freshwater bodies (especially creeks) typically do not have sufficient food available for the adult salmon diet, and they have used large amounts of energy swimming upriver, thus exhausting their own internal nutrient reserves. [61] [62] Spawning salmon also have programmed senescence, which is "characterized by immunosuppression and organ deterioration", making them more vulnerable to diseases. [38] [63] [64] Most zombie fish die within days of spawning, but some can last up to a couple of weeks. [59] Once the salmon die in the river, they are either scavenged by other animals, or they decompose and release inorganic nutrients to the plankton in the river and the riparian vegetation in the floodplain. [61]
The Pacific salmon are a classic example of a semelparous animal, which reproduce only once in their lifetime. Semelparity is sometimes called "big bang" reproduction, since the single reproductive event of semelparous organisms is usually large and fatal to the spawners. [65] It is an evolutionary strategy that concentrates all available resources into maximizing reproduction, at the expense of individual organism's life, which is common among insects but rare among vertebrates. [62] All six species of Pacific salmons live for many years in the ocean before swimming to the freshwater stream of its birth, spawning, and then dying. Most Atlantic salmon also die after spawning, but about 5 to 10% (mostly female) return to the ocean where they can recover and spawn again the next season. [18]
In the Pacific Northwest and Alaska, salmon is a keystone species, supporting wildlife from birds to bears and otters. [66] The bodies of salmon represent a transfer of nutrients from the ocean, rich in nitrogen, sulfur, carbon and phosphorus, to the forest ecosystem.
Grizzly bears function as ecosystem engineers, capturing salmon and carrying them into adjacent wooded areas. There they deposit nutrient-rich urine and faeces and partially eaten carcasses. It has been estimated that bears leave up to half the salmon they harvest on the forest floor, [67] [68] in densities that can reach 4,000 kilograms per hectare, [69] providing as much as 24% of the total nitrogen available to the riparian woodlands. [3] The foliage of spruce trees up to 500 m (1,600 ft) from a stream where grizzlies fish salmon have been found to contain nitrogen originating from fished salmon. [3]
Salmon continue to surprise us, showing us new ways in which their oceanic migrations eventually permeate entire terrestrial ecosystems. In terms of providing food and nutrients to a whole food web, we like to think of them as North America's answer to the Serengeti's wildebeest. [70]
Wolves normally hunt for deer. A 2008 study suggests that when the salmon run starts, wolves choose to fish for salmon, even if plenty of deer are still available. [71] "Selecting benign prey such as salmon makes sense from a safety point of view. While hunting deer, wolves commonly incur serious and often fatal injuries. In addition to safety benefits we determined that salmon also provides enhanced nutrition in terms of fat and energy." [70]
The upper reaches of the Chilkat River in Alaska has particularly good spawning grounds. Each year these attract a run of up to half a million chum salmon. As the salmon run up the river, bald eagles arrive in their thousands to feast at the spawning grounds. This results in some of the world's largest congregations of bald eagles. The number of participating eagles is directly correlated with the number of spawning salmon. [72]
Residual nutrients from salmon can also accumulate downstream in estuaries. A 2010 study suggests the density and diversity of many estuarine breeding birds in the summer "were strongly predicted by salmon biomass in the autumn". [73] Anadromous salmon provide nutrients to these "diverse assemblages ... ecologically comparable to the migrating herds of wildebeest in the Serengeti". [69]
In 1997, researchers noted that the future of salmon runs worldwide would depend on many factors, most of which are driven by human actions. Among the key driving factors are (1) harvest of salmon by commercial, recreational, and subsistence fishing, (2) alterations in stream and river channels, including construction of dikes and other riparian corridor modifications, (3) electricity generation, flood control, and irrigation supplied by dams, (4) alteration by humans of freshwater, estuarine, and marine environments used by salmon, coupled with aquatic changes due to climate and ocean circulatory regimes, (5) water withdrawals from rivers and reservoirs for agricultural, municipal, or commercial purposes, (6) changes in climate caused at least in part by human activities, (7) competition from non-native fishes, (8) salmon predation by marine mammals, birds, and other fish species, (9) diseases and parasites, including those from outside the native region, and (10) reduced nutrient replenishment from decomposing salmon. [74]
In 2009, NOAA advised that continued runoff into North American rivers of three widely used pesticides containing neurotoxins would "jeopardize the continued existence" of endangered and threatened Pacific salmon. [75] [76] Global warming could see the end of some salmon runs by the end of the century,[ according to whom? ] such as the Californian runs of Chinook salmon. [77] [78] A 2010 United Nations report said that increases in acidification of oceans would mean that shellfish such as pteropods, an important component of the ocean salmon diet, would be finding it more difficult to build their aragonite shells. [79] There were concerns[ by whom? ] that this too could endanger future salmon runs. [80]
In a 1982 video game called Salmon Run , the player takes the role of Sam the Salmon, swimming upriver to mate. Along the way he encounters waterfalls, a bear, fishermen, and seagulls.
In the Disney animated feature film, Brother Bear , Kenai and Koda reached the salmon run and met a large group of bears led by Tug at the Annual Salmon Run. Featuring the song "Welcome" by The Blind Boys of Alabama and Phil Collins.[ citation needed ]
External videos | |
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Grizzly Bears Catching Salmon on YouTube – Nature's Great Events: The Great Salmon Run | |
Bald Eagle catches salmon on YouTube – BBC Nature's Great Events - The Great Salmon Run | |
The Great Salmon Run on YouTube – BBC Nature's Great Events | |
Nimbus Hatchery Fish Ladder on YouTube | |
Life Cycle of Salmon on YouTube | |
Life Cycle of Salmon on YouTube – Discovery Channel | |
The Salmon's Lifecycle Atlantic Salmon Trust | |
Sockeye Salmon Run 2010 on YouTube | |
Spawning salmon constructing a redd on YouTube | |
Raising salmon on YouTube | |
Salmon life cycle song on YouTube |
Salmon is the common name for several commercially important 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. 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 endorheic populations in Central Asia.
Trout is a generic common name for numerous species of carnivorous freshwater ray-finned fishes belonging to the genera Oncorhynchus, Salmo and Salvelinus, all of which are members of the subfamily Salmoninae in the family Salmonidae. The word trout is also used for some similar-shaped but non-salmonid fish, such as the spotted seatrout/speckled trout.
Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres. Such migrations are usually done for better feeding or to reproduce, but in other cases the reasons are unclear.
Steelhead, or occasionally steelhead trout, is the anadromous form of the coastal rainbow trout (Oncorhynchus mykiss irideus) or Columbia River redband trout. Steelhead are native to cold-water tributaries of the Pacific basin in Northeast Asia and North America. Like other sea-run (anadromous) trout and salmon, steelhead spawn in freshwater, smolts migrate to the ocean to forage for several years and adults return to their natal streams to spawn. Steelhead are iteroparous, although survival is only approximately 10–20%.
The chum salmon, also known as dog salmon or keta salmon, is a species of anadromous salmonid fish from the genus Oncorhynchus native to the coastal rivers of the North Pacific and the Beringian Arctic, and is often marketed under the trade name silverbrite salmon in North America. The English name "chum salmon" comes from the Chinook Jargon term tsəm, meaning "spotted" or "marked"; while keta in the scientific name comes from Russian, which in turn comes from the Evenki language of Eastern Siberia. The term 'Dog Salmon' is most commonly used in Alaska and refers to the Salmon whose flesh Alaskans use to feed their dogs.
The Atlantic salmon is a species of ray-finned fish in the family Salmonidae. It is the third largest of the Salmonidae, behind Siberian taimen and Pacific Chinook salmon, growing up to a meter in length. Atlantic salmon are found in the northern Atlantic Ocean and in rivers that flow into it. Most populations are anadromous, hatching in streams and rivers but moving out to sea as they grow where they mature, after which the adults seasonally move upstream again to spawn.
The Chinook salmon is the largest and most valuable species of Pacific salmon. Its common name is derived from the Chinookan peoples. Other vernacular names for the species include king salmon, Quinnat salmon, Tsumen, spring salmon, chrome hog, Blackmouth, and Tyee salmon. The scientific species name is based on the Russian common name chavycha (чавыча).
The sockeye salmon, also called red salmon, kokanee salmon, blueback salmon, or simply sockeye, is an anadromous species of salmon found in the Northern Pacific Ocean and rivers discharging into it. This species is a Pacific salmon that is primarily red in hue during spawning. They can grow up to 84 cm in length and weigh 2.3 to 7 kg (5–15 lb). Juveniles remain in freshwater until they are ready to migrate to the ocean, over distances of up to 1,600 km (1,000 mi). Their diet consists primarily of zooplankton. Sockeye salmon are semelparous, dying after they spawn. Some populations, referred to as kokanee, do not migrate to the ocean and live their entire lives in fresh water.
Pink salmon or humpback salmon is a species of euryhaline ray-finned fish in the family Salmonidae. It is the type species of the genus Oncorhynchus, and is the smallest and most abundant of the seven officially recognized species of salmon. The species' scientific name is based on the Russian common name for this species gorbúša (горбуша), which literally means humpie.
The coho salmon is a species of anadromous fish in the salmon family and one of the five Pacific salmon species. Coho salmon are also known as silver salmon and is often sold as medium red salmon. The scientific species name is based on the Russian common name kizhuch (кижуч).
Oncorhynchus is a genus of ray-finned fish in the subfamily Salmoninae of the family Salmonidae, native to coldwater tributaries of the North Pacific basin. The genus contains twelve extant species, namely six species of Pacific salmon and six species of Pacific trout, all of which are migratory mid-level predatory fish that display natal homing and semelparity.
Puget Sound salmon recovery is a collective effort of federal, state and local authorities and non-profit coalitions of universities, scientists, business and industry aimed at restoring Pacific salmon and anadromous forms of Pacific trout (Oncorhynchus) within the Puget Sound region. The Puget Sound lies within the native range of the Pacific Salmon (Oncorhynchus) and two sea-run forms of Pacific trout, the coastal rainbow trout or steelhead and coastal cutthroat trout. Populations of Oncorhynchus have seen significant declines since the middle of the 19th century due to over fishing, habitat loss, pollution and disease. Salmon species residing in or migrating through the Puget Sound to spawning streams include Chum, Coho, Chinook, Sockeye, and Pink salmon. Pacific salmon require freshwater rivers for spawning and most major tributaries of the Puget Sound have salmon, steelhead and cutthroat trout spawning runs.
The Mattole River is a river on the north coast of California, that flows northerly, then westerly into the Pacific Ocean. The vast majority of its 62 miles (100 km) course is through southern Humboldt County, though a short section of the river flows through northern Mendocino County. Communities, from north to south, closely associated with the Mattole River include: Petrolia, Honeydew, Ettersburg, Thorn Junction, and Whitethorn. The river enters the ocean at the Mattole Estuary about 4 miles (6.4 km) west-southwest of Petrolia and 10 miles (16 km) south of Cape Mendocino.
The Baker River is an approximately 30-mile (48 km), southward-flowing tributary of the Skagit River in northwestern Washington in the United States. It drains an area of the high North Cascades in the watershed of Puget Sound north of Seattle, and east of Mount Baker. With a watershed of approximately 270 square miles (700 km2) in a complex of deep valleys partially inside North Cascades National Park, it is the last major tributary of the Skagit before the larger river reaches its mouth on Skagit Bay. The river flows through Concrete, Washington, near its mouth and has two hydroelectric dams owned by Puget Sound Energy.
Redwood Creek is a mostly perennial stream in Marin County, California. 4.7 miles (7.6 km) long, it drains a 7-square-mile (18 km2) watershed which includes the Muir Woods National Monument, and reaches the Pacific Ocean north of the Golden Gate at Muir Beach.
The coastal cutthroat trout, also known as the sea-run cutthroat trout, blue-back trout or harvest trout, is one of the four species of cutthroat trout found in Western North America. The coastal cutthroat trout occurs in four distinct forms. A semi-anadromous or sea-run form is the most well known. Freshwater forms occur in both large and small rivers and streams and lake environments. The native range of the coastal cutthroat trout extends south from the southern coastline of the Kenai Peninsula in Alaska to the Eel River in Northern California. Coastal cutthroat trout are resident in tributary streams and rivers of the Pacific basin and are rarely found more than 100 miles (160 km) from the ocean.
Natal homing, or natal philopatry, is the homing process by which some adult animals that have migrated away from their juvenile habitats return to their birthplace to reproduce. This process is primarily used by aquatic animals such as sea turtles and salmon, although some migratory birds and mammals also practice similar reproductive behaviors. Scientists believe that the main cues used by the animals are geomagnetic imprinting and olfactory cues. The benefits of returning to the precise location of an animal's birth may be largely associated with its safety and suitability as a breeding ground. When seabirds like the Atlantic puffin return to their natal breeding colony, which are mostly on islands, they are assured of a suitable climate and a sufficient lack of land-based predators.
Salmon population levels are of concern in the Atlantic and in some parts of the Pacific. Salmon are typically anadromous - they rear and grow in freshwater, migrate to the ocean to reach sexual maturity, and then return to freshwater to spawn. Determining how environmental stressors and climate change will affect these fisheries is challenging due to their lives split between fresh and saltwater. Environmental variables like warming temperatures and habitat loss are detrimental to salmon abundance and survival. Other human influenced effects on salmon like overfishing and gillnets, sea lice from farm raised salmon, and competition from hatchery released salmon have negative effects as well.
Fish go through various life stages between fertilization and adulthood. The life of fish start as spawned eggs which hatch into immotile larvae. These larval hatchlings are not yet capable of feeding themselves and carry a yolk sac which provides stored nutrition. Before the yolk sac completely disappears, the young fish must mature enough to be able to forage independently. When they have developed to the point where they are capable of feeding by themselves, the fish are called fry. When, in addition, they have developed scales and working fins, the transition to a juvenile fish is complete and it is called a fingerling, so called as they are typically about the size of human fingers. The juvenile stage lasts until the fish is fully grown, sexually mature and interacting with other adult fish.
The kokanee salmon, also known as the kokanee trout, little redfish, silver trout, kikanning, Kennerly's salmon, Kennerly's trout, or Walla, is the non-anadromous form of the sockeye salmon. There is some debate as to whether the kokanee and its sea-going relative are separate species; geographic isolation, failure to interbreed, and genetic distinction point toward a recent divergence in the history of the two groups. The divergence most likely occurred around 15,000 years ago when a large ice melt created a series of freshwater lakes and rivers across the northern part of North America. While some members of the salmon and trout family (salmonids) went out to sea (anadromous), others stayed behind in fresh water (non-anadromous). The separation of the sockeye and the kokanee created a unique example of sympatric speciation that is relatively new in evolutionary terms. While they occupy the same areas and habitats during the breeding season, when ocean-going sockeye salmon return to freshwater to spawn, the two populations do not mate with each other in some regions, suggesting speciation.