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 underwater view in an Alaskan stream during autumn.

Pink and Chum salmon (Oncorhynchus gorbuscha and O. keta) summer spawning migration in a tributary of Prince William Sound, Alaska.

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

Gaping male Coho Salmon (Oncorhynchus kisutch) challenging another fish in an Alaskan stream during autumn.

Jack and normal male Sockeye Salmon (Oncorhynchus nerka) in an Alaskan stream during summer.

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

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

Female Sockeye Salmon (Oncorhynchus nerka) attempting to oust a sneaker male by using the gape threat in an underwater view in an Alaskan stream during the summer.

Male Sockeye Salmon (Oncorhynchus nerka) attacking a competitor in an Alaskan stream during early summer.

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.

A Sockeye Salmon (Oncorhynchus nerka) alpha male attacks a challenger in an Alaskan stream during the summer; Alaska, United States of America

Coho Salmon, also known as Silver Salmon (Oncorhynchus kisutch) in the act of spawning in an Alaskan stream during autumn; Alaska, United States of America

Coho Salmon, also known as Silver Salmon (Oncorhynchus kisutch) in the act of spawning in an Alaskan stream during autumn; Alaska, United States of America

Coho Salmon, also known as Silver Salmon (Oncorhynchus kisutch) in the act of spawning in an Alaskan stream during autumn; Alaska, United States of America

Male Coho Salmon, also known as Silver salmon (Oncorhynchus kisutch) with battle scars from fighting with other males over spawning rights in an Alaskan stream during autumn; Alaska, United States of America

Coho salmon (also known as Silver Salmon, Oncorhynchus kisuch) in the act of spawning in an Alaskan stream; Alaska, United States of America

Coho Salmon, also known as Silver Salmon (Oncorhynchus kisutch) in the act of spawning in an Alaska stream during the autumn; Alaska, United States of America

Spawning female Chinook Salmon (also known as King Salmon, Oncorhynchus tshawytscha) in a tributary of the Copper River, Alaska during the summer; Alaska, United States of America

Coho Salmon, also known as Silver Salmon (Oncorhynchus kisutch) in the act of spawning in an Alaska stream during the autumn; Alaska, United States of America

Male Sockeye Salmon (also known as Red Salmon, Oncorhynchus nerka) digging in an Alaskan stream during the summer. This behavior is considered a displacement activity indicative of the male's frustration in not being able to spawn; Alaska, United...

Coho Salmon, also known as Silver Salmon (Oncorhynchus kisutch) in the act of spawning in an Alaska stream during the autumn; Alaska, United States of America

Coho Salmon, also known as Silver Salmon (Oncorhynchus kisutch) in the act of spawning in Sheridan River (Copper River Delta) tributary stream during autumn; Alaska, United States of America

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