Fish Facts

By Bill Hauser

Here are some facts about fish (mostly salmon) that I thought you might find interesting… some, I am sure you already know. This information originated from a web page in the Learning Center portion of the University of Washington, College of Ocean and Fishery Sciences web site.

Q. How many species of Pacific salmon are there?

A. Pacific salmon is a generic term used to describe those members of the genus Oncorhynchus that die after spawning. At present, there are seven species commonly referred to as Pacific salmon. Five species occur on both sides of the Pacific Ocean:

- Chinook salmon (Oncorhynchus tshawytscha) a.k.a. king salmon

- Chum salmon (Oncorhynchus keta) a.k.a. dog salmon

- Coho salmon (Oncorhynchus kisutch) a.k.a. silver salmon

- Pink salmon (Oncorhynchus gorbuscha) a.k.a. humpback salmon

- Sockeye salmon (Oncorhynchus nerka) a.k.a. red salmon

Two species occur only in Asia:

- Masu salmon (Oncorhynchus masou) a.k.a. yamame

- Amago salmon (Oncorhynchus rhodurus) a.k.a. biwamasu.

Q. Is it true that salmon return to spawn in freshwater areas where they were born?

A. Almost always. Some straying has been documented, but it is minor. Most spawning salmon return to the precise stream of their birth, sometimes overcoming great distances and hazardous river conditions to reach home.

Q. What is the difference between the Atlantic salmon and the Pacific salmon?

A. The Atlantic Salmon (Salmo salar) is actually one species within the genus Salmo. Pacific salmon are represented by seven different species and belong to the genus Oncorhynchus. The seven Pacific salmon species have life histories that are extremely complex and vary widely within and between species. However, all the Pacific salmon die shortly after spawning. Atlantic salmon have a much less variable range of life history strategies across the species and have high post-spawning mortality but are capable of surviving and spawning again.

Q. Is a steelhead a salmon or a trout?

A. The steelhead is a rainbow trout that migrates to sea as a juvenile and returns to fresh water as an adult to spawn. Unlike the Pacific salmon, the steelhead does not always die following spawning and may spawn more than once and return to the sea after each spawning. Until 1988, steelhead (the anadromous form of rainbow trout) was classified in the genus Salmo along with Atlantic salmon, brown trout, and several western trout species. With additional osteology and biochemistry data, biologists have now reclassified steelhead as members of the genus Oncorhynchus. The reason for this is that new information suggested that steelhead are more closely related to Pacific salmon than to brown trout and Atlantic salmon. As such, the American Fisheries Society/American Society of Ichthyologists & Herpetologists Committee on Names of Fishes voted unanimously to accept Oncorhynchus as the proper generic name. (For full scientific details, see: Smith, G. R., and R. F. Stearley. 1989. The classification and scientific names of rainbow and cutthroat trouts. Fisheries 14 (1): 4-10.) As such, the scientific name of steelhead was changed from Salmo gairdneri to Oncorhynchus mykiss. The generic names of the golden, Mexican golden, Gila, and Apache trouts were also changed to Oncorhynchus.

Q. Where do salmon go in the ocean?

A. Contrary to earlier beliefs, many salmon from North American rivers roam far at sea in the North Pacific Ocean and the Bering Sea. The oceanic distribution of salmon depends upon the species and point of origin. Sockeye and Chinook salmon from northwest Alaska, for example, may migrate across the Bering Sea to areas close to Kamchatka, U.S.S.R., and south of the Aleutian Islands into the North Pacific Ocean; the sockeye also migrate eastward to the Gulf of Alaska. Salmon such as the pink, chum, and coho from central and southeast Alaska, British Columbia, and Washington State, migrate out into the northeastern Pacific and Gulf of Alaska. Many steelhead from Washington and Oregon are known to migrate far at sea to areas off the Alaskan Peninsula. Some salmon migrate several thousand miles from the time they leave the rivers as juveniles until they return as adults. A chinook salmon tagged in the central Aleutian Islands and recovered a year later in the Salmon River, Idaho had traveled about 3,500 miles; a steelhead tagged south of Kiska Island in the western Aleutians was recovered about six months and 2,200 miles later in the Wynoochee River, Washington.

Q. What is a kokanee?

A. It is the landlocked subspecies of a sockeye salmon. The kokanee spends its entire life in fresh water and usually does not attain the size of its sea-migrating cousin.

Q. Do landlocked Pacific salmon die after spawning?

A. Yes. This phase of their life history is the same as their seagoing relatives.

Q. How large do salmon get?

A. Weights of 100 pounds and slightly over have been reported from European countries for the Atlantic salmon; the record for the largest of the Pacific species, chinook, is 126 pounds for a fish caught on commercial gear in Alaskan waters.

Q. What is the oldest known age of salmon and steelhead (in completed years)?

A. Chinook - 7; sockeye - 7; silver - 4; chum - 6; pink - 2; Atlantic salmon - 8; steelhead - 8 

Q. How old are salmon when they migrate from freshwater to the ocean?

A. Chinook – 12 to 16 months; Coho – 12 to 24 months; Pink and Chum - 1 week to a month; Sockeye -12 to 36 months

Q. How do salmon find their way back home to spawn after being out at sea?

A. They follow their noses. Salmon are able to detect the scent of their home streams and follow it upriver.

Q. How many eggs do salmon have?

A. Generally from 2,500 to 7,000 depending on species and size of fish. The chinook salmon generally produces the most and largest eggs. Larger females produce more eggs than smaller-sized females within a species.

Q. What proportion of young salmon come back as adults?

A. Releases from hatcheries of large fingerlings usually result in returns of one to five percent, but this depends on the species, too.

Q. What is the largest freshwater fish in North America?

A. The white sturgeon, Acipencer transmontanus. White sturgeon have attained a maximum size of approximately 18 feet and weight of about 2000 lbs. They are long-lived (probably in excess of 100 years), spawn in freshwater, and they are anadromous, like salmon (but they don't die after spawning). They are living dinosaurs (evolved approx. 200,000 years ago).

Q. Are there more mammal, bird, or fish species on Earth?

A. Fish! It’s believed there may be 28,000 different fish species.

Q. What fish can walk on land?

A. The climbing perch. This amazing fish, native to India, can walk on land in search of water when its water hole dries up.