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

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

Three male Sockeye Salmon (Oncorhynchus nerka) competing to spawn with one female during early summer in an Alaskan stream.

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

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

Dolly Varden (Salvelinus malma) male underwater in an Alaskan stream during autumn.

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.

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

Pink Salmon (Oncorhynchus gorbuscha) probes her redd in an Alaskan intertidal stream during summer.

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

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

Female Sockeye Salmon (Oncorhynchus nerka) makes a dig while alpha male guards downstream in an Alaskan stream during summer.

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) probes her redd while a male guards 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 in an Alaskan stream during the summer. Two competing males are lurking nearby, one is visible at the right edge of the frame and the other, a jack or precocial male, is visible...

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