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

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

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.

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

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

Headshot of a Coho Salmon (Oncorhyncchus kisutch) alpha male (foreground) and his mate reflected in the the shallow water of their spawning habitat in an Alaska stream during late autumn.

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

Coho Salmon (Oncorhynchus keta) at various stages of final maturation alongside late Sockeye Salmon (O. nerka) in an Alaskan stream during autumn.

Sockeye Salmon (Oncorhynchus nerka) spawning pair just upstream of a culvert (in background) in Alaska during late spring. The female has a putative lamprey scar.

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

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 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) spawning pair in an Alaska stream during the summer, South-central Alaska; Alaska, United States of America

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

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