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

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.

Female Chum Salmon (Oncorhynchus keta) sniffing the water where she is building her redd as a male guards.

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) 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 late autumn.

A Sockeye Salmon (Oncorhynchus nerka) female uses her anal to probe her redd while her alpha male guards from just downstream, Southcentral Alaska

Male Coho Salmon (Oncorhynchus kisutch) threatens with a gape while female is at the side of the creek in the background, Southcentral Alaska

Female Sockeye Salmon (Oncorhynchis nerka) raises a cloud of sediment during the process of excavating her redd, Southcentral Alaska

Female Sockeye Salmon (Oncorhynchus nerka) raising a cloud of sediment while digging her redd in an Alaskan stream during the summer.

A female Sockeye Salmon (Oncohynchus nerka) nudges a male away from her redd so that she can work on it, 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

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) probes her redd while a male guards 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 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

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