Oncorhynchus facts for kids
Quick facts for kids OncorhynchusTemporal range: Late Miocene – recent
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| Sockeye salmon, Oncorhynchus nerka Female (above) and male in mating season Note male with kype (hooked snout) |
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Scientific classification  |
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| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Salmoniformes |
| Family: | Salmonidae |
| Subfamily: | Salmoninae |
| Genus: | Oncorhynchus Suckley, 1861 |
| Type species | |
| Oncorhynchus gorbuscha (Walbaum, 1792)
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| Species | |
Oncorhynchus is a group of fish that includes the Pacific salmon and Pacific trout. These fish belong to the family called Salmonidae. The name Oncorhynchus comes from ancient Greek words meaning "lump" or "bend" and "snout." This refers to the hooked jaw, called a "kype," that male salmon develop during their mating season.
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Where They Live
These salmon and trout naturally live in waters that flow into the Pacific Ocean. Their home range stretches from the Bering Sea area down to places like Taiwan in the west and Mexico in the east. In North America, some types of O. clarkii live in the Rocky Mountains and Great Basin. Others live in the Rio Grande and rivers that flow into the Mississippi River Basin, which eventually goes to the Gulf of Mexico.
Many Oncorhynchus species have also been moved to new waters around the world. They have successfully started new wild populations there.
Their Amazing Journey: Life Cycles
The six types of Pacific salmon in the Oncorhynchus group are anadromous. This means they are born in fresh water, travel to the ocean to grow, and then return to fresh water to lay their eggs. They are also semelparous, which means they die after they lay their eggs.
Sometimes, tiny parasites can make these fish weak. This can make it harder for them to complete their long journey back to their spawning grounds. Fish that are infected are less likely to finish their migration.
However, some types of Oncorhynchus mykiss, known as steelhead, are iteroparous. This means they can lay eggs multiple times in their lives. The coastal cutthroat trout is considered "semi-anadromous." It spends some time in the ocean but usually stays closer to its home stream.
How They Evolved
Scientists have found very old trout-like fossils in Idaho that are about 7 million years old. These fossils seem to be from early Oncorhynchus fish. This tells us that Oncorhynchus fish were living in Pacific waters long ago. It also shows that different types of Oncorhynchus, like rainbow and cutthroat trout, and Pacific salmon, had already started to become separate species.
The split between Oncorhynchus (Pacific salmon and trout) and Salmo (Atlantic salmon) happened even earlier, possibly around 20 million years ago. One amazing fossil fish from this group is O. rastrosus, also called the saber-toothed salmon. This huge fish was about 9 feet (2.7 meters) long!
Scientists have studied the Mitochondrial DNA (mtDNA) of Pacific trout and salmon to understand their family tree. The results sometimes differ from what fossils show. However, it's generally agreed that chum, pink, and sockeye salmon branched off later than other species. Some scientists think that the way Oncorhynchus species changed over time might be linked to big tectonic shifts (movements of Earth's plates) in the Pacific Northwest. These changes could have led to new habitats and challenges, causing the fish to adapt and form new species.
A Special Case: Kokanee Sockeye
An interesting example of how new species can form is the kokanee sockeye. These are landlocked sockeye salmon, meaning they live their whole lives in lakes and don't go to the ocean. They evolve differently from sockeye that migrate to the ocean.
In some lakes, two groups of kokanee sockeye live in the same lake but lay their eggs in different places and at different times. They also eat different foods. This means they don't compete with each other or try to breed together. These kokanee salmon show how new species can form even when living in the same area. They are separate groups that don't mix their genes.
Why Oncorhynchus Numbers Are Dropping
Since the mid-1800s, the number of Pacific salmon has generally gone down. For example, experts believe that by 1933, salmon populations in the Columbia River basin were less than 20% of what they were before 1850. By 2008, some estimated that Pacific salmon in the Pacific Northwest were less than 10% of their original numbers.
Today, many of the salmon runs we see are mostly made up of salmon raised in hatcheries, not wild salmon. Many local groups of Pacific trout, especially rainbow trout and cutthroat trout, have also seen their numbers drop. Some types of Oncorhynchus are now listed as endangered or threatened. Sadly, two types of Oncorhynchus clarki are now extinct.
Many things cause these declines:
- Overfishing: Too many fish are caught.
- Habitat loss: Places where salmon live and breed are destroyed or damaged.
- Hatcheries: Fish raised in hatcheries can sometimes cause problems for wild fish.
- New species: Fish introduced from other places can compete with or interbreed with native salmon. For example, the yellowfin cutthroat trout became extinct because non-native rainbow trout were introduced into its waters.
In 2020, researchers also reported that Pacific salmon are getting smaller. This affects the ecosystem and people who rely on them. This change is linked to climate change and competition from more wild and hatchery salmon.
How Hatcheries Affect Salmon
When wild salmon numbers dropped due to overfishing, hatcheries were asked to raise more fish to help supply fisheries. However, hatcheries can't perfectly copy the natural environment of wild salmon. This often leads to differences in how hatchery fish look and behave compared to wild fish.
These differences can come from changes in their genes or from living in different environments. For example, fishing often catches larger fish, so wild salmon have become smaller over time. But in hatcheries, larger salmon are often chosen for breeding. This means hatchery salmon tend to be much bigger than wild salmon.
When these larger hatchery fish are released, they can compete with wild salmon for space, food, and other things. Some hatchery salmon even act like predators towards smaller wild salmon. Also, large numbers of hatchery fish can disrupt the natural social interactions of wild salmon, as hatchery fish tend to be more aggressive.
So, while hatcheries help provide fish for people, they can also put wild salmon populations at risk. Wild salmon numbers are still dropping as more hatchery fish are released. Efforts to limit hatcheries to help wild salmon are often difficult because hatcheries support many states' economies by providing over 70% of the salmon caught for fun and sale.
The Impact of Too Much Fishing
People around the world catch Pacific salmon for food. Over the last century, a lot of Pacific salmon have been caught by people fishing for fun, by small-scale fishers, and by large commercial fishing boats. In fact, since the 1970s, the amount of Pacific salmon caught has almost tripled.
As more fish are caught, scientists have noticed that the average size of salmon has gotten smaller. For example, Japanese chum salmon got 11 to 32 percent lighter between 1970 and 1988. This is partly because fishing gear often catches larger fish. So, being smaller became a helpful trait for survival.
However, studies show that larger salmon produce more offspring that survive. Salmon usually have more babies if they wait longer to reproduce and grow bigger. So, smaller salmon mean fewer surviving babies, which slows down population growth. This drop in how many salmon are produced is partly due to overfishing.
Today, salmon numbers seem to be increasing, but the effects of overfishing from the 1970s and 80s are still seen. The average size of salmon is still smaller than it was before that time.
Protecting Oncorhynchus
Canadian Efforts
Scientists have found that sockeye salmon are strongly affected by water temperature, and their reactions vary by region. Canada uses its Species at Risk Act to protect different types of salmon and the many areas where they live.
COSEWIC, a Canadian group that protects species, has listed several salmon types as endangered. These include the Interior Fraser River Coho, the Cultus Lake Sockeye, and the Sakinaw Lake Sockeye.
In British Columbia, sockeye salmon from four different river systems were certified as sustainable fisheries in 2010 by the Marine Stewardship Council (MSC). This certification means they are being fished in a way that protects the environment. The Pink Salmon Fishery was also certified in 2011, and the Chum Salmon Fisheries began their review for certification in 2012.
American Efforts
The US government is working on a national plan for salmon populations. The Pacific Salmon Stronghold Conservation Act aims to create special protected areas for salmon. Another plan, the Wild Salmon Policy, started in 2005 and focuses on protecting salmon off the coasts. Even local plans have begun, like one in Oregon that started in 2013 for its southernmost watershed.
In Alaska, there are eight known groups of salmon that survive well. Also, young salmon (called smolts) leaving fresh water for the ocean can greatly affect how well different salmon groups survive. The Alaska Department of Fish and Game first received MSC certification for sustainable seafood in 2000. They left the program in 2012. The Annette Island Reserve salmon fishery, managed by the Metlakatla Indian community, received its sustainability certification in 2011.
The Wild Salmon Center is a non-profit group that works to protect salmon worldwide. They have helped protect river areas for salmon in Russia and on the US west coast. They also fight illegal fishing, support sustainable fisheries, and create new habitats for salmon.
Russian Efforts
Poaching (illegal fishing) is a big problem for Oncorhynchus salmon and steelhead in Russia. It's thought that illegal catches are 1.5 times higher than reported catches. The Wild Salmon Center is working with Russian authorities to improve systems that track salmon. This helps markets tell the difference between legal, sustainable salmon and illegal salmon.
The Wild Salmon Center has also helped protect some areas for salmon populations. Working with the WWF, they helped get a Sockeye Salmon fishery certified as sustainable in 2012. The Iturup Island Pink and Chum Salmon Fishery was the first Russian salmon fishery to get MSC certification in 2009. Other certified fisheries include the Northeast Sakhalin Island Pink Salmon (2012) and the Ozernaya River Sockeye Salmon (2012). The Aniva Bay Pink Salmon and the Sakhalin Island Pink salmon are currently being reviewed by the MSC.
New Homes and Fish Farms
Several types of Oncorhynchus have been successfully introduced into waters where they didn't naturally live. They have even started new wild populations there. The rainbow trout (Oncorhynchus mykiss) is the most common species to be introduced.
Rainbow trout, Chinook salmon (Oncorhynchus tshawytscha), and Coho salmon (Oncorhynchus kisutch) have created wild populations in the Great Lakes. Chinook salmon have also done this in New Zealand. Raising Chinook and Coho salmon and rainbow trout in aquaculture (fish farms) is a big business in Chile and Australia. Chinook salmon from Chile have been released into Argentinean rivers, and Coho and Sockeye Salmon and Rainbow Trout have been stocked in Patagonia.
Types of Oncorhynchus Species
Scientists have studied these fish for many years. In 1989, studies showed that trout from the Pacific basin were more closely related to Pacific salmon than to Salmo fish, like brown trout or Atlantic salmon, which live in the Atlantic basin. Because of this, in 1989, scientists moved the Rainbow, Cutthroat, and other Pacific basin trout into the Oncorhynchus group.
Currently, 12 species and many subspecies (smaller groups within a species) are recognized in this genus.
| Image | Scientific name | Common Name | Subspecies | Distribution |
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Oncorhynchus apache (R. R. Miller, 1972) | Apache trout, Arizona trout | Upper Salt River and Little Colorado River watersheds | |
| Oncorhynchus chrysogaster (Needham & Gard, 1964) | Mexican golden trout | Headwaters of the Fuerte, Sinaloa, and Culiacán River drainages in the Sierra Madre Occidental | ||
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Oncorhynchus clarki (J. Richardson, 1836) | cutthroat trout |
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Pacific Northwest coast from Alaska to northern California, Cascade Range, Great Basin, and Rocky Mountains |
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Oncorhynchus gilae (R. R. Miller, 1950) | Gila trout | Gila River in Arizona and New Mexico | |
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Oncorhynchus gorbuscha (Walbaum, 1792) | pink salmon, humpback salmon | Pacific and Arctic coastal waters and rivers, from California to Canada; and from Siberia to Japan | |
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Oncorhynchus kawamurae (D. S. Jordan & E. A. McGregor, 1925) | kunimasu, black kokanee | Lake Saiko | |
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Oncorhynchus keta (Walbaum, 1792) | chum salmon, dog salmon, keta salmon, silverbrite salmon | Yukon River and Amur River basin in Asia. Also in the North Pacific, Korea, Japan, Okhotsk and Bering Seas, British Columbia, and Alaska to California | |
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Oncorhynchus kisutch (Walbaum, 1792) | coho salmon, silver salmon, silvers | Both sides of the North Pacific Ocean, from Japan and Russia, around the Bering Sea to Alaska, and south to California | |
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Oncorhynchus masou (Brevoort, 1856) | masu salmon, cherry salmon, Japanese salmon, seema |
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Kamchatka, Kuril Islands, Sakhalin, and Primorsky Krai south through Korea, Taiwan, and Japan |
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Oncorhynchus mykiss (Walbaum, 1792) | rainbow trout, steelhead, ocean trout, redband trout |
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Pacific basin, from Kamchatka Peninsula in Russia, east along the Aleutian Islands, throughout Alaska, British Columbia, and south along the west coast of the U.S. to northern Mexico |
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Oncorhynchus nerka (Walbaum, 1792) | sockeye salmon, red salmon, blueback salmon, kokanee | Columbia River in the eastern Pacific and northern Hokkaidō Island in Japan in the western Pacific | |
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Oncorhynchus tshawytscha (Walbaum, 1792) | Chinook salmon, blackmouth, black salmon, chub salmon, Columbia River salmon, hookbill salmon, king salmon, Quinnat salmon, spring salmon, Tyee salmon, winter salmon | Ventura River in California in the south to Kotzebue Sound in Alaska in the north |
See also
In Spanish: Salmones y truchas del Pacífico para niños
