Misplaced Pages

#309690

70-465: All other members of Salmoninae Salmon ( / ˈ s æ m ən / ; pl. : 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

140-506: A common ancestor . The Eocene salmon's fossil from British Columbia provides evidence that the divergence between Pacific and Atlantic salmon had not yet occurred 40 million years ago. Both the fossil record and analysis of mitochondrial DNA suggest the divergence occurred 10 to 20 million years ago during the Miocene . This independent evidence from DNA analysis and the fossil record indicate that salmon divergence occurred long before

210-744: A monophyletic group. The order Salmoniformes first appeared during the Santonian and Campanian stages of the Late Cretaceous , and is most closely related to pike and mudminnows in the order Esociformes , to the extent that some authors have grouped the Esociformes within the Salmoniformes. Although it is assumed that salmon and pike diverged from one another during the Cretaceous, no definitive salmonids appear before

280-423: A closer examination of the salmonid genome, and has allowed for a more precise dating of the whole-genome duplication of the group, that places the latest possible date for the event at 88 million years ago. This more precise dating and examination of the salmonid whole-genome duplication event has allowed more speculation on the radiation of species within the group. Historically, the whole-genome duplication event

350-442: A few species of salmon remain in fresh water throughout their life cycle, the majority are anadromous and migrate to the ocean for maturation: in these species, 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

420-475: A fish returns after just one year's sea feeding, it is called a grilse in Canada, Britain, and Ireland. Grilse may be present at spawning, and go unnoticed by large males, releasing their own sperm on the eggs. Prior to spawning, depending on the species , 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). All change from

490-712: A future in aquaculture that eliminates the need for land, freshwater, or fertilizer to raise fish. Salmon population levels are of concern in the Atlantic and in some parts of the Pacific. The population of wild salmon declined markedly in recent decades, especially North Atlantic populations, which spawn in the waters of western Europe and eastern Canada, and wild salmon in the Snake and Columbia River systems in northwestern United States. Salmoninae Salmonidae ( / s æ l ˈ m ɒ n ɪ d iː / , lit. "salmon-like")

560-567: A high demand for wild forage fish . As a predator, salmon require large nutritional intakes of protein , and farmed salmon consume more fish than they generate as a final product. On a dry weight basis, 2–4 kg of wild-caught fish are needed to produce one kilogram of salmon. As the salmon farming industry expands, it requires more forage fish for feed, at a time when 75% of the world's monitored fisheries are already near to or have exceeded their maximum sustainable yield . The industrial-scale extraction of wild forage fish for salmon farming affects

630-547: A lot of work on Henneguya salminicola was done by scientists at the Pacific Biological Station in Nanaimo in the mid-1980s, in particular, an overview report which states, "the fish that have the longest fresh water residence time as juveniles have the most noticeable infections. Hence in order of prevalence , coho are most infected followed by sockeye, chinook, chum and pink. As well, the report says, at

700-568: A single row of sharp teeth . Although the smallest salmonid species is just 13 cm (5.1 in) long for adults, most salmonids are much larger, with the largest reaching 2 m (6 ft 7 in). All salmonids are migratory fish that spawn in the shallow gravel beds of freshwater headstreams , spend the growing juvenile years in rivers , creeks , small lakes and wetlands , but migrate downstream upon maturity and spend most of their adult lives at much larger waterbodies. Many salmonid species are euryhaline and migrate to

770-411: A technically demanding kind of sport fishing , not necessarily intuitive for beginning fishermen. A conflict exists between commercial fishermen and recreational fishermen for the right to salmon stock resources . Commercial fishing in estuaries and coastal areas is often restricted so enough salmon can return to their natal rivers where they can spawn and be available for sport fishing. On parts of

SECTION 10

#1732772426310

840-542: Is a family of ray-finned fish that constitutes the only currently extant family in the order Salmoniformes ( / s æ l ˈ m ɒ n ɪ f ɔːr m iː z / , lit. "salmon-shaped"), consisting of 11 extant genera and over 200 species collectively known as " salmonids " or " salmonoids ". The family includes salmon (both Atlantic and Pacific species), trout (both ocean-going and landlocked), char , graylings , freshwater whitefishes , taimens and lenoks , all coldwater mid- level predatory fish that inhabit

910-858: Is a major contributor to the world production of farmed finfish, representing about US$ 10 billion annually. Other commonly cultured fish species include tilapia , catfish , sea bass , carp and bream . Salmon farming is significant in Chile , Norway , Scotland , Canada and the Faroe Islands ; it is the source for most salmon consumed in the United States and Europe. Atlantic salmon are also, in very small volumes, farmed in Russia and Tasmania , Australia. Salmon are carnivorous , and need to be fed meals produced from catching other wild forage fish and other marine organisms. Salmon farming leads to

980-673: Is an archaic salmonid, representing an important stage in salmonid evolution. Fossil scales of coregonines are known from the Late Eocene or Early Oligocene of California. A gap appears in the salmonine fossil record after E. driftwoodensis until about 7 million years ago ( mya ), in the Late Miocene , when trout-like fossils appear in Idaho , in the Clarkia Lake beds . Several of these species appear to be Oncorhynchus —

1050-439: Is quite high (perhaps as high as 40 to 50%). To lay her roe , the female salmon uses her tail (caudal fin), to create a low-pressure zone, lifting gravel to be swept downstream, excavating a shallow depression, called a redd. The redd may sometimes contain 5,000 eggs covering 2.8 m (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

1120-963: Is strictly a fish parasite that cannot live in or affect warm blooded animals, including man". According to Klaus Schallie, Molluscan Shellfish Program Specialist with the Canadian Food Inspection Agency , " Henneguya salminicola is found in southern B.C. also and in all species of salmon. I have previously examined smoked chum salmon sides that were riddled with cysts and some sockeye runs in Barkley Sound (southern B.C., west coast of Vancouver Island ) are noted for their high incidence of infestation." Sea lice , particularly Lepeophtheirus salmonis and various Caligus species, including C. clemensi and C. rogercresseyi , can cause deadly infestations of both farm-grown and wild salmon. Sea lice are ectoparasites which feed on mucus, blood, and skin, and migrate and latch onto

1190-401: Is the fourth of its kind to happen in the evolutionary lineage of the salmonids, with two having occurred commonly to all bony vertebrates, and another specifically in the teleost fishes. Extant salmonids all show evidence of partial tetraploidy, as studies show the genome has undergone selection to regain a diploid state. Work done in the rainbow trout ( Onchorhynchus mykiss ) has shown that

1260-480: Is under development in Alaska . There, the young salmon are released into the ocean far from any wild salmon streams. When it is time for them to spawn, they return to where they were released, where fishermen can catch them. An alternative method to hatcheries is to use spawning channels. These are artificial streams , usually parallel to an existing stream, with concrete or rip-rap sides and gravel bottoms. Water from

1330-788: The Atlantic salmon , found in both sides of the North Atlantic , as well as more than 40 other species commonly named as trout . The genus Oncorhynchus contains 12 recognised species which occur naturally only in the North Pacific, six of which are known as Pacific salmon while the remainder are considered trout. Outside their native habitats, Chinook salmon have been successfully introduced in New Zealand and Patagonia , while coho , sockeye and Atlantic salmon have been established in Patagonia, as well.     Both

1400-624: The Cook Inlet Aquaculture Association , as a way to increase salmon populations in situations where they have declined due to overharvesting , construction of dams and habitat destruction or fragmentation . Negative consequences to this sort of population manipulation include genetic "dilution" of the wild stocks. Many jurisdictions are now beginning to discourage supplemental fish planting in favour of harvest controls, and habitat improvement and protection. A variant method of fish stocking , called ocean ranching,

1470-596: The Eocene . The Salmonidae first appear in the fossil record in the Early Eocene with Eosalmo driftwoodensis , a stem- salmonine , which was first described from fossils found at Driftwood Creek , central British Columbia , and has been recovered from most sites in the Eocene Okanagan Highlands . This genus shares traits found in all three subfamily lineages. Hence, E. driftwoodensis

SECTION 20

#1732772426310

1540-564: The Great Lakes of North America , Patagonia in South America and South Island of New Zealand . The Modern English term salmon is derived from Middle English : samoun , samon and saumon , which in turn are from Anglo-Norman : saumon , from Old French : saumon , and from Latin : salmō (which in turn might have originated from salire , meaning "to leap".). The unpronounced "l" absent from Middle English

1610-489: The Japanese word for trout. On the other hand, the steelhead and sea trout , the anadromous forms of rainbow trout and brown trout respectively, are from the same genera as salmon and live identical migratory lives, but neither is termed "salmon" . The extinct Eosalmo driftwoodensis , the oldest known Salmoninae fish in the fossil record , helps scientists figure how the different species of salmon diverged from

1680-525: The Pacific Northwest and Alaska , salmon are keystone species . The migration of salmon represent a massive retrograde nutrient transfer, rich in nitrogen , sulfur , carbon and phosphorus , from the ocean to the inland freshwater ecosystems . Predation by piscivorous land animals (such as ospreys , bears and otters ) along the journey serve to transfer the nutrients from the water to land, and decomposition of salmon carcass benefits

1750-457: The Pacific coast of Canada , the louse-induced mortality of pink salmon in some regions is commonly over 80%. The risk of injury caused by underwater pile driving has been studied by Dr. Halvorsen and her co-workers. The study concluded that the fish are at risk of injury if the cumulative sound exposure level exceeds 210 dB relative to 1 μPa s. As can be seen from the production chart at

1820-513: The Quaternary glaciation began the cycle of glacial advance and retreat. There are several other species of fish which are colloquially called "salmon" but are not true salmon. Of those listed below, the Danube salmon or huchen is a large freshwater salmonid closely related (from the same subfamily) to the seven species of salmon above, but others are fishes of unrelated orders , given

1890-672: The Salmo and Oncorhynchus genera also contain a number of trout species informally referred to as salmon. Within Salmo , the Adriatic salmon ( Salmo obtusirostris ) and Black Sea salmon ( Salmo labrax ) have both been named as salmon in English , although they fall outside the generally recognized seven salmon species. The masu salmon ( Oncorhynchus masou ) is actually considered a trout ("cherry trout") in Japan , with masu actually being

1960-415: The biomass transfer provided by their mass migration from oceanic to inland waterbodies. Current salmonids comprise three main clades taxonomically treated as subfamilies : Coregoninae ( freshwater whitefishes ), Thymallinae ( graylings ), and Salmoninae ( trout , salmon , char , taimens and lenoks ). Generally, all three lineages are accepted to allocate a suite of derived traits indicating

2030-497: The forest ecosystem . In the case of Pacific salmon , most (if not all) of the salmon that survive to reach the headwater spawning grounds will die after laying eggs and their dead bodies sink to cover the gravel beds, with the nutrients released from the biodegradation of their corpses providing a significant boost to these otherwise biomass -poor shallow streams. Grizzly bears function as ecosystem engineers , capturing salmon and carrying them into adjacent dry land to eat

2100-522: The myrtle zone . These dams can be overtopped at high tide and hold water at low tide. This provides refuges for juvenile salmon so they do not have to swim into large channels where they are subject to predation by larger fish. It has been discovered that rivers which have seen a decline or disappearance of anadromous lampreys , loss of the lampreys also affects the salmon in a negative way. Like salmon, anadromous lampreys stop feeding and die after spawning, and their decomposing bodies release nutrients into

2170-473: The ocean as adults and live like sea fish , then return to their freshwater birthplace to reproduce . However, populations of several species are restricted to fresh waters (i.e. landlocked) throughout their lives. Folklore has it that the 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;

Salmon - Misplaced Pages Continue

2240-590: The otolith (annuli), analogous to the growth rings visible in a tree trunk. Freshwater growth shows as densely crowded rings, sea growth as widely spaced rings; spawning is marked by significant erosion as body mass is converted into eggs and milt. Freshwater streams and estuaries provide important habitat for many salmon species. They feed on terrestrial and aquatic insects , amphipods , and other crustaceans while young, and primarily on other fish when older. Eggs are laid in deeper water with larger gravel and need cool water and good water flow (to supply oxygen) to

2310-683: The sea or brackish estuaries as soon as they approach adulthood, returning to the upper streams only to reproduce. Such sea-run life cycle is described as anadromous , and other freshwater salmonids that migrate purely between lakes and rivers are considered potamodromous . Salmonids are carnivorous predators of the middle food chain , feeding on smaller fish, crustaceans , aquatic insects and larvae , tadpoles and sometimes fish eggs (even those of their own kind), and in turn being preyed upon by larger predators. Many species of salmonids are thus considered keystone organisms important for both freshwater and terrestrial ecosystems due to

2380-559: The subarctic and cool temperate waters of the Northern Hemisphere . The Atlantic salmon ( Salmo salar ), whose Latin name became that of its genus Salmo , is also the eponym of the family and order names. Salmonids have a relatively primitive appearance among teleost fish, with the pelvic fins being placed far back, and an adipose fin towards the rear of the back. They have slender bodies with rounded scales and forked tail fins , and their mouths contain

2450-985: The superorder Protacanthopterygii . The only extant family within Salmoniformes, Salmonidae, is divided into three subfamilies and around 10 genera containing about 220 species . The concepts of the number of species recognised vary among researchers and authorities; the numbers presented below represent the higher estimates of diversity: Prosopium [REDACTED] Stenodus [REDACTED] Coregonus [REDACTED] Thymallus [REDACTED] Salmo [REDACTED] Salvelinus (incl. Salvethymus ) [REDACTED] Oncorhynchus [REDACTED] Brachymystax Parahucho [REDACTED] Hucho [REDACTED] Order Salmoniformes The following table shows results of hybrid crossbreeding combination in Salmonidae. note :- : The identical kind, O : (survivability), X : (Fatality) Subfamily Detarioideae

2520-477: The North American West Coast salmon sport fishing has completely replaced inshore commercial salmon fishing. In most cases, the commercial value of a salmon sold as seafood can be several times less than the value attributed to the same fish caught by a sport fisherman. This is "a powerful economic argument for allocating stock resources preferentially to sport fishing". Salmon aquaculture

2590-569: The Pacific Ocean, the second host releases a stage infective to salmon. The parasite is then carried in the salmon until the next spawning cycle. The myxosporean parasite that causes whirling disease in trout has a similar life cycle. However, as opposed to whirling disease, the Henneguya infestation does not appear to cause disease in the host salmon—even heavily infected fish tend to return to spawn successfully. According to Dr. Kieser,

2660-520: The Pliocene. Suggestions have gone back as far as the Early Miocene (about 20 mya). Based on the most current evidence, salmonids diverged from the rest of teleost fish no later than 88 million years ago, during the late Cretaceous . This divergence was marked by a whole-genome duplication event in the ancestral salmonid, where the diploid ancestor became tetraploid . This duplication

2730-432: The adjacent stream is piped into the top of the channel, sometimes via a header pond, to settle out sediment. Spawning success is often much better in channels than in adjacent streams due to the control of floods, which in some years can wash out the natural redds. Because of the lack of floods, spawning channels must sometimes be cleaned out to remove accumulated sediment. The same floods that destroy natural redds also clean

2800-607: The common name "salmon" simply due to similar shapes, behaviors and niches occupied: Salmon eggs are laid in freshwater streams typically at high latitudes. The eggs hatch into alevin or sac fry. The fry quickly develop into parr with camouflaging vertical stripes. The parr stay for six months to three years in their natal stream before becoming smolts, which are distinguished by their bright, silvery colour with scales that are easily rubbed off. 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

2870-538: The current genus for Pacific salmon and Pacific trout. The presence of these species so far inland established that Oncorhynchus was not only present in the Pacific drainages before the beginning of the Pliocene (~5–6 mya), but also that rainbow and cutthroat trout , and Pacific salmon lineages had diverged before the beginning of the Pliocene. Consequently, the split between Oncorhynchus and Salmo (Atlantic salmon and European trout) must have occurred well before

Salmon - Misplaced Pages Continue

2940-430: The developing embryos. 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 their associated wetlands provide vital nursery areas for the salmon prior to their departure to the open ocean. Wetlands not only help buffer

3010-469: The elimination of beavers from large parts of the river system, salmon runs plummeted, even in the absence of many of the factors usually associated with the demise of salmon runs. Salmon recruitment can be affected by beavers' dams because dams can: Beaver dams are able to nurture salmon juveniles in estuarine tidal marshes where the salinity is less than 10 ppm. Beavers build small dams of generally less than 60 cm (2 ft) high in channels in

3080-821: The estuary from silt and pollutants, but also provide important feeding and hiding areas. Salmon not killed by other means show greatly accelerated deterioration ( phenoptosis , or "programmed aging") 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 . Salmon are mid- level carnivores whose diet change according to their life stage. Salmon fry predominantly feed upon zooplanktons until they reach fingerling sizes, when they start to consume more aquatic invertebrates such as insect larvae , micro crustaceans and worms . As juveniles (parrs), they become more predatory and actively prey upon aquatic insects , small crustaceans, tadpoles and small bait fishes . They are also known to breach

3150-439: The fish. There they deposit nutrient-rich urine and feces and partially eaten carcasses. Bears preparing for hibernation tend to preferentially consume the more nutrient- and energy -rich salmon roes and brain over the actual flesh , and are estimated to discard up to half the salmon they've harvested uneaten on the forest floor, in densities that can reach 4,000 kg (8,800 lb) per hectare, providing as much as 24% of

3220-449: The genome is still partially-tetraploid. Around half of the duplicated protein-coding genes have been deleted, but all apparent miRNA sequences still show full duplication, with potential to influence regulation of the rainbow trout's genome. This pattern of partial tetraploidy is thought to be reflected in the rest of extant salmonids. The first fossil species representing a true salmonid fish ( E. driftwoodensis ) does not appear until

3290-564: 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 (depending on the species) 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. When

3360-682: The left, the global capture reported by different countries to the FAO of commercial wild salmon has remained fairly steady since 1990 at about one million tonnes per year. This is in contrast to farmed salmon (below) which has increased in the same period from about 0.6 million tonnes to well over two million tonnes. Nearly all captured wild salmon are Pacific salmon . The capture of wild Atlantic salmon has always been relatively small, and has declined steadily since 1990. In 2011 only 2,500 tonnes were reported. In contrast, about half of all farmed salmon are Atlantic salmon. Recreational salmon fishing can be

3430-458: The longer the fish remain in fresh water, and they then deteriorate further after they spawn, when they are known as kelts. In all species of Pacific salmon, the mature individuals die within a few days or weeks of spawning, a trait known as semelparity . Between 2 and 4% of Atlantic salmon kelts survive to spawn again, all females. However, even in those species of salmon that may survive to spawn more than once ( iteroparity ), postspawning mortality

3500-427: The middle Eocene. This fossil already displays traits associated with extant salmonids, but as the genome of E. driftwoodensis cannot be sequenced, it cannot be confirmed if polyploidy was present in this animal at this point in time. This fossil is also significantly younger than the proposed salmonid divergence from the rest of the teleost fishes, and is the earliest confirmed salmonid currently known. This means that

3570-446: The parasitic infection into a number of cysts that contain milky fluid. This fluid is an accumulation of a large number of parasites. Henneguya and other parasites in the myxosporean group have complex life cycles, where the salmon is one of two hosts. The fish releases the spores after spawning. In the Henneguya case, the spores enter a second host, most likely an invertebrate, in the spawning stream. When juvenile salmon migrate to

SECTION 50

#1732772426310

3640-520: The percent of straying depends on the species of salmon. 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, with Norway being the world's largest producer of farmed salmon, followed by Chile . They are also highly prized game fish for recreational fishing , by both freshwater and saltwater anglers . Many species of salmon have since been introduced and naturalized into non-native environments such as

3710-524: The preferred prey of seals and sea lions, which can eat 30 lampreys to every salmon, allowing more adult salmon to enter the rivers to spawn without being eaten by the marine mammals. According to Canadian biologist Dorothy Kieser, the myxozoan parasite Henneguya salminicola is commonly found in the flesh of salmonids. It has been recorded in the field samples of salmon returning to the Haida Gwaii Islands . The fish responds by walling off

3780-407: The problems of rising costs for buying hatchery fish feed . Yet another attractive alternative is the increased use of seaweed . Seaweed provides essential minerals and vitamins for growing organisms. It offers the advantage of providing natural amounts of dietary fiber and having a lower glycemic load than grain-based fish meal . In the best-case scenario, widespread use of seaweed could yield

3850-463: The regular streams. Spawning channels preserve the natural selection of natural streams, as there is no benefit, as in hatcheries, to use prophylactic chemicals to control diseases. Farm-raised salmon are fed the carotenoids astaxanthin and canthaxanthin to match their flesh colour to wild salmon to improve their marketability. Wild salmon get these carotenoids , primarily astaxanthin, from eating shellfish and krill . One proposed alternative to

3920-405: 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. This results in ring formation around an earbone called

3990-509: The salmon population. This system is referred to as ranching . It was very common in countries such as Sweden, before the Norwegians developed salmon farming, but is seldom done by private companies. As anyone may catch the salmon when they return to spawn, a company is limited in benefiting financially from their investment. Because of this, the ranching method has mainly been used by various public authorities and non-profit groups, such as

4060-441: The salmonids have a ghost lineage of approximately 33 million years. Given a lack of earlier transition fossils, and the inability to extract genomic data from specimens other than extant species, the dating of the whole-genome duplication event in salmonids was historically a very broad categorization of times, ranging from 25 to 100 million years in age. New advances in calibrated relaxed molecular clock analyses have allowed for

4130-481: 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 . Salmon are typically anadromous : they hatch in the shallow gravel beds of freshwater headstreams and spend their juvenile years in rivers , lakes and freshwater wetlands , migrate to

4200-421: The silvery blue of a fresh-run fish from the sea to a darker colour. Salmon can make amazing 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

4270-540: The skin of wild salmon during free-swimming, planktonic nauplii and copepodid larval stages, which can persist for several days. Large numbers of highly populated, open-net salmon farms can create exceptionally large concentrations of sea lice; when exposed in river estuaries containing large numbers of open-net farms, many young wild salmon are infected, and do not survive as a result. Adult salmon may survive otherwise critical numbers of sea lice, but small, thin-skinned juvenile salmon migrating to sea are highly vulnerable. On

SECTION 60

#1732772426310

4340-455: The stream. Also, along with species like rainbow trout and Sacramento sucker , lampreys clean the gravel in the rivers during spawning. Their larvae, called ammocoetes, are filter feeders which contribute to the health of the waters. They are also a food source for the young salmon, and being fattier and oilier, it is assumed predators prefer them over salmon offspring, taking off some of the predation pressure on smolts. Adult lampreys are also

4410-532: The survivability of other wild predatory fish which rely on them for food. Research is ongoing into sustainable and plant-based salmon feeds. Intensive salmon farming uses open-net cages, which have low production costs. It has the drawback of allowing disease and sea lice to spread to local wild salmon stocks. Another form of salmon production, which is safer but less controllable, is to raise salmon in hatcheries until they are old enough to become independent. They are released into rivers in an attempt to increase

4480-496: The time the studies were conducted, stocks from the middle and upper reaches of large river systems in British Columbia such as Fraser , Skeena , Nass and from mainland coastal streams in the southern half of B.C., "are more likely to have a low prevalence of infection." The report also states, "It should be stressed that Henneguya , economically deleterious though it is, is harmless from the view of public health . It

4550-466: The total nitrogen available to the riparian woodlands . 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 the fished salmon. Beavers also function as ecosystem engineers; in the process of tree-cutting and damming , beavers alter the local ecosystems extensively. Beaver ponds can provide critical habitat for juvenile salmon . An example of this

4620-596: The use of wild-caught fish as feed for the salmon, is the use of soy -based products. This should be better for the local environment of the fish farm, but producing soy beans has a high environmental cost for the producing region. The fish omega-3 fatty acid content would be reduced compared to fish-fed salmon. Another possible alternative is a yeast-based coproduct of bioethanol production, proteinaceous fermentation biomass. Substituting such products for engineered feed can result in equal (sometimes enhanced) growth in fish. With its increasing availability, this would address

4690-415: The water to attack terrestrial insects such as grasshoppers and dragonflies , as well as consuming fish eggs (even those of other salmon). As adults, salmon behave like other mid-sized pelagic fish , eating a variety of sea creatures including smaller forage fish such as lanternfish , herrings , sand lances , mackerels and barracudina . They also eat krill , squid and polychaete worms . In

4760-433: Was later added as a Latinisation to make the word closer to its Latin root. The term salmon has mostly displaced its now dialectal synonym lax , in turn from Middle English : lax , from Old English : leax , from Proto-Germanic : * lahsaz from Proto-Indo-European : *lakso- . The seven commercially important species of salmon occur in two genera of the subfamily Salmoninae . The genus Salmo contains

4830-644: Was seen in the years following 1818 in the Columbia River Basin. In 1818, the British government made an agreement with the U.S. government to allow U.S. citizens access to the Columbia catchment (see Treaty of 1818 ). At the time, the Hudson's Bay Company sent word to trappers to extirpate all furbearers from the area in an effort to make the area less attractive to U.S. fur traders. In response to

4900-556: Was thought to be the reason for the variation within Salmonidae. Current evidence done with molecular clock analyses revealed that much of the speciation of the group occurred during periods of intense climate change associated with the last ice ages, with especially high speciation rates being observed in salmonids that developed an anadromous lifestyle. Together with the closely related orders Esociformes ( pikes and mudminnows ), Osmeriformes ( true smelts ) and Argentiniformes ( marine smelts and barreleyes ), Salmoniformes comprise

#309690