Biology and Ecosystems

Why do salmon eggs come in different colors?

Salmon eggs (roe) range in color from pale yellowish-orange to dark reddish-orange. The color varies both by species and within species and is determined by water temperature, sediment composition, age, and other factors. The eggs vary in size from the tiny sockeye roe (average ¼ inch or 5.6 mm) to the large chum roe (average almost ½ inch or 8.3 mm). Also, if a salmon egg does not get fertilized, it can lose its bright hue and turn a milky shade with patches of color.

The red color of eggs comes from carotenoids (antioxidant pigments) that the salmon get from their diet. Salmon deposit carotenoids in both their skin and eggs in preparation for spawning. It protects tissue from oxidative damage and helps regulate immune response. In a spawning adult, the red color is a signal of fitness and status, and is used to attract mates.

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How do salmon know where their home is when they return from the ocean?

Salmon come back to the stream where they were 'born' because they 'know' it is a good place to spawn; they won't waste time looking for a stream with good habitat and other salmon. Scientists believe that salmon navigate by using the earth’s magnetic field like a compass. When they find the river they came from, they start using smell to find...

Animated image of a Sockeye Salmon swimming

How far do salmon travel?

Salmon first travel from their home stream to the ocean, which can be a distance of hundreds of miles. Once they reach the ocean, they might travel an additional 1,000 miles to reach their feeding grounds.

Why do salmon change color and die after they spawn?

Salmon change color to attract a spawning mate. Pacific salmon use all their energy for returning to their home stream, for making eggs, and digging the nest. Most of them stop eating when they return to freshwater and have no energy left for a return trip to the ocean after spawning. After they die, other animals eat them (but people don't) or...

Brown bears (Ursus arctos) and Chum (Salmon Oncorhynchus)

How long do salmon usually live?

Most salmon species live 2 to 7 years (4 to 5 average). Steelhead trout can live up to about 11 years.

When can salmon be seen migrating to their spawning area?

Most Pacific salmon can be seen migrating from spring though fall, depending on the species. Most adult Atlantic salmon migrate up the rivers of New England beginning in spring and continuing through the fall as well, with the migration peaking in June.

Male atlantic salmon showing a kype in lower jaw

Why are there so few salmon left?

There are many reasons for the decline in salmon populations. Logging an area around a stream reduces the shade and nutrients available to the stream and increases the amount of silt or dirt in the water, which can choke out developing eggs. Dams cause fish to die from the shock of going through the turbines and from predators that eat the...

Image: Releasing a Radio-Tagged Adult Chinook

How many species of salmon are there and how large can they get?

There are seven species of Pacific salmon. Five of them occur in North American waters: chinook, coho, chum, sockeye, and pink. Masu and amago salmon occur only in Asia. There is one species of Atlantic salmon. Chinook/King salmon are the largest salmon and get up to 58 inches (1.5 meters) long and 126 pounds (57.2 kg). Pink salmon are the...

Image: Salmon Are Carefully Released Using Buckets

Where are salmon most endangered?

Certain populations of sockeye salmon, coho salmon, chinook salmon, and Atlantic salmon are listed as endangered. Sockeye salmon from the Snake River system are probably the most endangered salmon. Coho salmon in the lower Columbia River may already be extinct. Salmon are not endangered worldwide. For example, most populations in Alaska are...

Kasilof coho salmon with radio tag antenna in it's mouth

Are salmon endangered worldwide?

No, salmon are not endangered worldwide. For example, most populations in Alaska are healthy. Some populations in the Pacific Northwest are much healthier than others. These healthy populations usually occupy protected habitats such as the Hanford Reach on the Columbia River and streams of Olympic National Park.

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Date published: April 20, 2016

Community flood protection may also help endangered salmon to thrive

Building a river setback levee to reduce the risk of flood for a community may also help endangered fish species to thrive, according to the results of a novel computer model reported by the U.S. Geological Survey.

Attribution: Northwest - Pacific Islands, Region 9: Columbia-Pacific Northwest

collage of scientists conducting science related to each mission are

Date published: January 5, 2015

Endangered Salmon Population Monitored with eDNA for First Time

CORVALLIS, Ore. — Scientists from the U.S. Geological Survey and Washington State University have discovered that endangered Chinook salmon can be detected accurately from DNA they release into the environment. The results are part of a special issue of the journal Biological Conservation on use of environmental DNA to inform conservation and management of aquatic species.

Attribution: Ecosystems, Region 9: Columbia-Pacific Northwest

Date published: June 6, 2013

New Method Monitors Riverbed and Flows to Protect Spawning Salmon

USGS scientists took high-tech sensors typically found in devices such as smart phones and embedded them into a new method to monitor riverbed movements that can help protect spawning habitat for endangered salmon. Developed in cooperation with Seattle Public Utilities for the Cedar River, the new method is published in the Journal of Hydrology.

Attribution: Region 9: Columbia-Pacific Northwest

Date published: March 6, 2001

Removal of Obsolete Forest Roads Can Reduce Erosion and Sediment That Impair Salmon-bearing Streams

Removing abandoned forest roads and restoring the natural characteristics of slopes and stream channels in the Redwood National and State Parks in northern California have substantially reduced the delivery of sediment to salmon-bearing streams, according to a research geologist with the U.S. Geological Survey.

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