Ocean bright Coho Salmon (Oncorhynchus kisutch) on their spawning migration in an underwater view in an Alaskan stream during autumn.

Pink and Chum salmon (Oncorhynchus gorbuscha and O. keta) summer spawning migration in a tributary of Prince William Sound, Alaska.

Ocean bright Coho Salmon (Oncorhynchus kisutch) on their spawning migration in an underwater view in an Alaskan stream during autumn.

Pink salmon (Oncorhynchus gorbuscha) probes her redd while her alpha male guards in an Alaska stream during summer.

Pink and Chum salmon (Oncorhynchus gorbuscha and O. keta) summer spawning migration in a tributary of Prince William Sound, Alaska.

Pink and Chum salmon (Oncorhynchus gorbuscha and O. keta) summer spawning migration in a tributary of Prince William Sound, Alaska.

Sockeye Salmon (Oncorhynchus nerka) spawning pair positioned over a redd that is under construction in an Alaskan stream during early summer.

Sockeye Salmon (Oncorhynchus nerka) spawning pair positioned over a redd that is under construction in an Alaskan stream during early summer.

Sockeye Salmon (Oncorhynchus nerka) spawning pair positioned over a redd that is under construction in an Alaskan stream during early summer.

Dolly Varden (Salvelinus malma) and one Coastal Cutthroat Trout (Oncorhynchus clarkii clarkii) in a deep pool in an Alaskan stream during summer.

Sockeye Salmon (Oncorhynchus nerka) males assert their dominance by raising their snout while on spawning grounds in an Alaskan stream during early summer.

A female Sockeye Salmon (Oncorhynchus nerka) uses her anal fin to probe her redd while a jack is positioned downstream. Underwater view in an Alaskan stream during the summer.

Sockeye Salmon, also known as Red Salmon (Oncorhynchus nerka) spawning pair in an Alaskan stream during the summer; Alaska, United States of America

Sockeye Salmon, also known as Red Salmon (Oncorhynchus nerka) spawning pair in an Alaskan stream during the summer; Alaska, United States of America

A Sockeye Salmon, also known as Red Salmon (Oncorhynchus nerka) pair in the act of spawning in an Alaskan stream during the summer; Alaska, United States of America

Sockeye Salmon, also known as Red Salmon (Oncorhynchus nerka) female in breeding (nuptial) coloration in an Alaskan stream during the summer; Alaska, United States of America

Mature Sockeye Salmon, also known as Red Salmon (Oncorhynchus nerka) male in nuptial (breeding) coloration in an Alaskan stream during the summer; Alaska, United States of America

Sockeye Salmon, also known as Red Salmon (Oncorhynchus nerka) spawning pair in an Alaska stream during the summer, South-central Alaska; Alaska, United States of America

A male Pink Salmon (Oncorhynchus gorbuscha) among others of the same species and Dolly Varden Charr (southern form; Salvelinus malma lordi) form a dense school at the bottom of a deep pool during their spawning migration in an Alaskan stream during...

Sockeye Salmon, also known as Red Salmon (Oncorhynchus nerka) male crosses over a female as part of courtship in an Alaskan stream during the summer; Alaska, United States of America

Sockeye Salmon, also known as Red Salmon (Oncorhynchus nerka) male threatening a challenger by also raising his snout in an Alaskan stream during the summer; Alaska, United States of America

A female Sockeye Salmon, also known as Red Salmon (Oncorhynchus nerka) attacking a female who is excavating a redd that is too close to hers in an Alaskan stream during the summer; Alaska, United States of America

Chum Salmon (Oncorhynchus keta) spawning migration in an Alaskan stream during the summer.