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

Coho Salmon (Oncorhynchus kisutch) fry near a submerged rootwad in an Alaskan stream during spring.

Sockeye Salmon (Oncorhynchus nerka) in the act of spawning in an Alaska 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) in the act of spawning in an Alaska stream during summer.

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

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

Male Coho Salmon (Oncorhynchus kisutch) responding to the female's probing by gaping, underwater view in an Alaskan stream during autumn.

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

Underwater view of a coho salmon (Oncorhynchus kisutch) spawning in Power Creek near Cordova, Alaska in the autumn; Alaska, United States of America

Two hook-nose alpha male Coho Salmon (Oncorhynchus kisutch) contenders competing to spawn with adjacent female that is hovering over her under-construction redd in an Alaskan stream in autumn; Alaska, United States of America

Coho Salmon (Oncorhynchus kisutch) female uses her anal fin to probe her redd as her alpha male guards, Southcentral Alaska

Anticipating spawning, male Coho Salmon, also known as Silver Salmon (Oncorhynchus kisutch) approach a female probing her redd in an Alaskan stream during the summer; Alaska, United States of America

Coho Salmon, also known as Silver Salmon (Oncorhynchus kisutch) crosses over the tail end of 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) 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

Sockeye Salmon, also known as Red Salmon (Oncorhynchus nerka) probes her redd while a male guards in an Alaskan stream during the summer; Alaska, United States of America

Coho Salmon (Oncorhynchus kisutch) in the act of spawning in an Alaska stream during autumn.