Chum Salmon (Oncorhynchus keta) spawning; Underwater view in an Alaskan stream during summer.

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

Sockeye Salmon (Oncorhynchus nerka) spawning pair in an Alaskan stream during early summer.

Early Coho Salmon (Oncorhynchus kisutch) and late Sockeye Salmon (O. nerka) arriving at spawning grounds in an Alaskan stream during autumn.

Female Coho Salmon (Oncorhynchus kisutch) flanked by two alpha male contenders in an Alaska stream during late autumn.

Ocean bright Coho Salmon (Oncorhynchus kisutch) on their spawning migration in an Alaskan stream during late summer.

Female Coho Salmon (Oncorhynchus kisutch) digging her redd in an underwater view, Southcentral Alaska, Autumn

A Sockeye Salmon (Oncorhynchus nerka) spawning pair Underwater view in an Alaskan stream during the summer.

Female Coho Salmon (Oncorhynchus kisutch) probing behavior induces the male to false spawn, underwater view in an Alaskan stream during autumn.

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

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

Sockeye Salmon (Oncorhynchus nerka) in the act of spawning in an Alaska stream during 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) spawning in an Alaskan stream during the summer. The small male is a jack; 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

Female Sockeye Salmon, also known as Red Salmon (Oncorhynchus nerka), covers her redd immediately after spawning as the male guards in an Alaskan stream during the summer. Sperm that has not drifted downstream clouds the water above the redd; Alaska,...

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

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...

Coho Salmon (Oncorhynchus kisutch) spawning pair in an Alaskan stream during autumn, Southcentral Alaska