Most of us are familiar with the uniquely orange or pink-fleshed fish commonly stocked in grocery stores. Salmon is a healthy food, and it tastes excellent. Still, the one to two species of salmon in our grocery store delis only represents a handful of species from the diverse family Salmonidae. This family contains over 200 species nested into ten genera and spread across three subfamilies.
Salmonidae includes salmon, which usually migrate from freshwater to the ocean, a life history trait referred to as anadromy, and trout, which typically remain in freshwater throughout their lives. Here we will scratch the surface of this specious group and discuss anadromous salmon species within the two genera Salmo and Oncorhynchus.
Salmon live short, fast lives and provide a source of food for many inland creatures. They typically spend very little of their lives in the freshwater streams where they are born and migrate to the ocean. Upon maturity, most salmon species return to the same streams they were born in using their remarkable memory and sense of smell.
Salmon synchronize their migration events, traveling upstream in large numbers during consistent times of the year to spawn in large groups. Other animals like bears, eagles, raccoons, river otters, and herons take advantage of these migrations to snag a nutritious meal.
Humans also benefit from the recreational and commercial harvest of salmon. Recreationally speaking, salmon are among the most popular sportfish behind sunfish and catfish. Harvested in bulk, these species fuel huge fisheries worth hundreds of millions of dollars. In addition, salmon hatcheries take advantage of the salmon’s homing ability by rearing young individuals in a facility with specially scented water. Those salmon leave the facility, with their adipose fin removed so recreational fishers can identify hatchery salmon, grow up in the ocean, and return to the same facility where they are harvested.
To the average consumer, salmon is a healthy source of fatty acids and other nutrients while also being chock-full of protein, but there is much more to this grocery store item than some might realize.
Salmon Species
1) Chinook salmon (Oncorhynchus tshawytscha)
The Chinook salmon is the largest of the Pacific salmon species, with an average length of around 36 inches (91 cm) and a maximum length of 58 inches (147.32 cm). As a result, this species is the most expensive at fish markets; this fact, coupled with its rarity (compared to other salmon species), earns it the title of “King Salmon.” The filet from a Chinook salmon is more melt-in-your-mouth than different types of salmon due to its higher fat content.
Generally, Chinook salmon are silver-colored with dark flecks along their dorsal surface and some red coloration on their dorsal fin. However, during the breeding season, breeding adults turn remarkably dark, with red blushing all over the body. From May to July, adult Chinook salmon between three and seven years of age travel upriver from the sea to spawn. Typically, individuals travel back to their natal streams, using their keen sense of smell and nearly all their energy reserves to get there. Once they arrive at the appropriate spawning grounds, females dig nests or redds into the substrate and lay their eggs. After this spawning event, the adults die, having used all their energy to make the remarkable journey from the ocean to the spawning grounds. This reproductive strategy is shared among all salmon species.
Hatchlings will either migrate immediately to salt water within their first year of life or spend an entire year in freshwater, after which they migrate out to the ocean. As they age, the size of their prey items increases from tiny plankton and insects to larger animals like squid and herring.
In some areas, Chinook salmon have been intentionally introduced as a sportfish and are known to compete with native trout species. Additionally, some populations of Chinook salmon have become landlocked, especially those introduced to the Great Lakes region. These populations use the Great Lakes instead of the ocean and spawn in connected rivers.
The Chinook salmon is not of conservation concern.
2) Coho salmon (Oncorhynchus kisutch)
The coho salmon occupies the same range as the Chinook salmon. However, due to its slightly smaller size, the coho salmon can travel up smaller streams and tributaries during migration events. A typical coho salmon comes in at around 24 to 28 inches (61 to 71 cm) in length, with females being smaller than males. Once they reach sexual maturity, adults migrate back to their natal rivers to spawn. Breeding adults sport a very dark coloration with intense red bellies and blushing on their heads. Males also develop a hooked jaw. This coloration is similar to, although less intense than, that observed in Chinook salmon.
Once hatched, young fish spend at least one winter in freshwater before migrating to the ocean, where they prey upon small fish and insects. While in the sea, most coho salmon spend the next 1 to 4 years of their lives eating larger fish species, squid, and prominent individuals who can even hunt birds.
This species is not as common in filet markets as the sockeye or the Chinook, but a substantial community of sport fishers treasure this fish. When harvested commercially, they are usually sold canned or frozen.
The coho salmon is not of conservation concern in the United States.
3) Chum salmon (Oncorhynchus keta)
The chum salmon’s range extends the most northward of any salmon species. They appear similar to other salmon species as juveniles and young adults but come spawning season, they transform into dark green fish with rusty purple tiger stripes. The chum salmon is the second-largest salmon species and grows to around 23 inches (58 cm) long on average.
Chum salmon spawn closer to the ocean than coho salmon, although both species generally occupy similar watersheds. As a result, young chum salmon spend only a few days in freshwater before migrating to the sea.
Their flesh is drier than the more popular Chinook or pink salmon. Another name for this species of salmon is dog salmon, coined because it was historically fed to sled dogs. Another possible explanation for this nickname is the large canine-like teeth developed by breeding males, who notably do not eat during their spawning migrations.
The chum salmon is not endangered or threatened.
4) Sockeye (Oncorhynchus nerka)
The characteristic bright red-bodied, green-headed salmon most often seen in media, Disney’s Brother Bear, for example, is the sockeye or blueback salmon. Compared to other species, this species’ range does not extend as far south as the coho or the chinook salmon’s. Additionally, sockeye salmon are among the smallest salmon species at around 18 inches (46 cm) in length on average.
Sockeye salmon come in two forms, the anadromous sockeye salmon and the landlocked kokanee salmon. Sockeye fry spend about a year or two in lakes before migrating to sea. In their native range, kokanee salmon have evolved independently from sockeye salmon, although there is occasional mixing between the two subgroups. In many states, kokanee salmon have been intentionally introduced as a sportfish or as a forage fish for more desirable sportfish.
The sockeye salmon is not endangered or threatened.
5) Steelhead/Rainbow trout (Oncorhynchus mykiss)
Like the sockeye salmon, this next species is split between two groups based on migration habits: steelhead salmon and rainbow trout. The former makes the traditional salmon migrate to the ocean, whereas the latter remains landlocked or otherwise trapped in freshwater bodies. Easily recognizable by the rose-colored stripe running down this fish’s sides, the rainbow trout is one of North America’s most ubiquitous and popular sportfish. While it can be found worldwide, O. mykiss is only native to the west coast, coastal Alaska, and parts of eastern Russia. This salmon is a large species with an average length of around 24 inches (61 cm).
Young O. mykiss develop with a generous yolk sac which they depend on until they are large enough to hunt for themselves. Prey items for young O. mykiss include invertebrates and algae. Anadromous individuals spend about 1 to 3 years in their natal streams before going to the ocean, typically sticking around in freshwater longer than coho or sockeye salmon. Once in the sea, they prey upon fish and cephalopods, and upon maturity, they make their way back to where they were born to begin the cycle anew.
Steelhead salmon and rainbow trout are not of conservation concern.
6) Pink salmon (Oncorhynchus gorbuscha)
With the nickname “Humpie,” adult male pink salmon develop exaggerated body features from a pronounced humped back to prominent teeth and intense coloration. This species is the smallest of Pacific salmon, coming in at around 20 inches (51 cm) on average. In the west, pink salmon are found canned or filet; in Japan, they are prized for their caviar or “ikura.” The abundance and subsequent harvest of pink salmon vary yearly, with odd-numbered years being more abundant than even-numbered years.
They also have a shorter lifespan, with fry migrating to sea as soon as possible and only spending around 18 months in the ocean before migrating back upstream. Introduced populations in the Great Lakes use the large lakes in place of the sea but maintain their short lifestyle. Pink salmon are known for their lack of precision when returning to their natal streams, often choosing to spawn in streams several kilometers from where they were born.
Pink salmon are not of conservation concern.
7) Cherry salmon (Oncorhynchus masou)
Cherry salmon, or masu as they are known in Japan, are endemic to the western Pacific in coastal Russia and Japan. This species and pink salmon make up the bulk of Japanese salmon harvests. As a whole, cherry salmon are not of conservation concern, but there are several subspecies with restricted ranges that are considered endangered and threatened with extinction. Primary threats to the cherry salmon subspecies include habitat degradation and alteration due to damming and residential development. Some attempts have been made to introduce cherry salmon to the United States with little success.
Young cherry salmon sport distinct spotting patterns and a reddish hue. Young fish lose these spots as they age, turning into completely silver-colored fish. Breeding adults develop red and green “tiger stripes” and are similar in appearance to chum salmon, although cherry salmon lack any pronounced “hump” as seen in chum salmon. This species grows to be around 20 inches (51 cm). Seafaring cherry salmon predate upon crustaceans, only occasionally making a meal of small fish.
8) Atlantic salmon (Salmo salar)
While most anadromous salmon species are found in the Pacific, there is one species of Atlantic salmon known simply as the Atlantic salmon. There are both landlocked and anadromous forms of Atlantic salmon, and those that make it to the ocean tend to grow more than those that do not. A third variety, known as the Gullspång salmon, is the largest variety of Atlantic salmon. Once threatened by excessive harvest, Atlantic salmon have been intentionally introduced to other regions of the United States as a sportfish and as a conservation effort to prevent species extinction.
Young Atlantic salmon, or “smolts,” have a spotted pattern on top of a silvery or golden coloration. Once smolts reach 5 to 6 inches (13 to 15 cm) in length, they migrate to the ocean. Atlantic salmon spend either one or two years in the sea before returning to their natal streams to spawn. An average adult will be around 15 inches (38 cm) long. Breeding adults are olive-colored with hints of red and an abundance of black dots along their bodies
Only the Gullspång salmon is currently of conservation concern. However, in Sweden, concerted conservation practices are in place to prevent the extinction of this variety of Atlantic salmon.
