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Questions and Answers About Salmon

A list of questions asked by students and answers provided by a USGS-WFRC Scientist.

Sockeye - USGS, WFRC. (Public domain.)

What is the largest type of salmon?

Chinook/King Salmon are the largest and get up to 58" long and 126 pounds. While the chinook may be the largest in North America, there are larger species in Asia.

What is the smallest salmon?

Pink salmon are the smallest and get up to 30" long and up to 12 pounds (average 3 to 5 pounds)

Do all salmon survive from hatching to birth?

No, many die before hatching, some due to not being fertilized, some due to disease.

How long do salmon usually live?

2 to 7 years (4 to 5 average).

What are some of the main reasons salmon die or are killed?

Environmental conditions, predation, fishing, disease.

Are there bones in salmon?

Yes, salmon have bones.

How far do salmon travel?

Salmon travel the distance from their home stream to the ocean which can be hundreds of miles and they may travel in the ocean up to Alaska and far out to sea, some up to 1,000 miles.

What happens if a salmon cannot find its stream?

Some salmon will try to find the right stream until they use up all their energy and die but most would simply try to find other salmon to spawn with. These fish stray into other streams to spawn if they are lucky.

Is it difficult for salmon to go up fish ladders, and if so, why?

Engineers design fish ladders so it will not be difficult, each step of the ladder is a gradual increase in height and there are places for fish to rest. Usually a ladder is put in a place that is difficult or impossible for the fish to pass any other way. It may be hard for the fish to find the ladder, especially in a big river.

How do you transfer salmon eggs?

Salmon eggs are very sensitive to movement early in their development, so they are not moved until they are "eyed" (their eyes are showing through the egg). They are handled gently and either kept in water or kept moist and cool during transport. They can survive for over a day like this because they use very little oxygen at this stage.

About how many salmon from one spawning pair live from the time they're laid to the time they return as adults?

Each female salmon can have between 1,500 and 10,000 eggs. Only a few (0 to 10) of these eggs will survive to be adult salmon. A population maintaining its size only produces one adult from each parent on average (two adults from each spawning pair), but it will be higher in some years and lower in others.

What effects do man-made objects have on salmon?

Many man-made objects hurt salmon by blocking their migration route or making it much more difficult. Dams on rivers of course are the main problem to salmon migration. Other man-made objects are designed to help salmon, like fish ladders. Fish ladders help the adult salmon migrate up a river and work very well. Dams are more of a problem for small salmon migrating downstream because they end up going through the turbines if they can't find the passages placed in the dam to help them. Roads across and alongside streams can be a problem if dirt from the road clogs up the gravel in the stream.

How many species of salmon are there?

There are eight species of Pacific salmon: chinook, coho, chum, sockeye, pink, steelhead trout, masu and amago salmon (two Asian species).

Are there specific seasons in which salmon can only be found?

Yes, most salmon can be seen migrating during the fall (September through November). Steelhead trout migrate in the summer and winter but don't spawn until spring and are harder to observe than salmon (because the water is higher in spring and they don't change color).

Why do salmon change color when they spawn?

Salmon change color to attract a spawning mate.

Why do salmon die after they spawn?

Salmon use all their energy for returning to their home stream, for making eggs and digging the nest. Most salmon 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 they decompose, adding nutrients to the stream. Steelhead trout, however, continue to eat in freshwater and many survive and return to the ocean. These fish can grow another year and then return to spawn again.

How do salmon know to go to the ocean in the first place?

We don't know. They must have a genetic cue to head downstream when their bodies are ready to change to a saltwater environment (they are called salmon smolts when their bodies change and they migrate to the ocean).

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

We think they can tell directions in the ocean by the earth's magnetic field acting like a compass. When they find the river they came from they start using smell to find their way back to their home stream. They build their "smell memory-bank" when they start migrating to the ocean as young fish.

What do salmon eat?

Salmon eat insects when they are young and eventually eat other fish when they are older.

Why do salmon come back to the same stream?

Salmon come back to the same stream they were "born" in because they "know" it is a good place to spawn and they won't waste time looking for another stream with good habitat and other fish to spawn with.

Why are there so few salmon left?

In the Pacific Northwest, salmon populations are doing very poorly. There are many reasons for this. 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 which eat the disoriented fish as they emerge from the dam. Fishing is another source of death that can contribute to the decline of salmon. The weather also affects the amount of food that is available to salmon in the ocean.

What can we do to save salmon?

Some things we can do to save salmon are to protect their stream habitat, help restore streams that have been damaged, reduce fishing, and help find ways to increase salmon survival through the dams.