Underwater view of a female sockeye salmon (Oncorhynchus nerka) in Power Creek near Cordova, Alaska in the summer; Alaska, United States of America

Underwater view of male sockeye salmon (Oncorhynchus nerka) aggression in Power Creek near Cordova, Alaska in the summer; Alaska, United States of America

Underwater view of a male sockeye salmon (Oncorhynchus nerka) in Power Creek near Cordova, Alaska in the summer; Alaska, United States of America

Underwater view of a male sockeye salmon (Oncorhynchus nerka) in Power Creek near Cordova, Alaska in the summer; Alaska, United States of America

Animals

Underwater view of a male sockeye salmon (Oncorhynchus nerka) in Power Creek near Cordova, Alaska in the summer; Alaska, United States of America

Underwater view of a sockeye salmon (Oncorhynchus nerka) spawning pair and a challenger male in Power Creek near Cordova, Alaska in the summer; Alaska, United States of America

Underwater view of a sockeye salmon (Oncorhynchus nerka) spawning pair and a sneaker male in Power Creek near Cordova, Alaska in the summer; Alaska, United States of America

Underwater view of developing sockeye salmon (Oncorhynchus nerka) eggs in Power Creek near Cordova and Prince William Sound; Alaska, United States of America

Underwater view of migrating pink salmon (Oncorhynchus gorbuscha) in Hartney Creek, with a Dolly Varden trout (Salvelinus malma) lurking near the bottom, near Cordova, Alaska in the summer; Alaska, United States of America

Underwater view of a sockeye salmon (Oncorhynchus nerka) spawning pair and a challenger male in Eccles Creek near Cordova, Alaska in the summer; Alaska, United States of America

Underwater view of maturing coho salmon (Oncorhynchus kisutch) holding in a pool in Hartney Creek near Cordova, Alaska in autumn; Cordova, Alaska, United States of America

Underwater view of King Salmon (Class Actinopterygii) in Moose Creek, a tributary of the Deshka River, South-central Alaska; 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) male crosses over 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

While her alpha male guards, a female Sockeye Salmon, also known as Red Salmon (Oncorhynchus nerka) excavates her redd in an Alaskan stream near Cordova, South-central Alaska; 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

Female Chinook Salmon, also known as King Salmon (Oncorhynchus tshawytscha) prior to spawning in a tributary of the Deshka River, South-central Alaska; 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

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

Chinook Salmon, also known as King Salmon (Oncorhynchus tshawytscha) schooled in a holding pattern prior to spawning in a tributary of the Deshka River in summer; Alaska, United States of America

Incidental tree branch bites can result from the aggressive behavior of male Sockeye Salmon, also known as Red Salmon (Oncorhynchus nerka) competing to spawn in an Alaskan stream during the summer; Alaska, United States of America

Underwater view of a female pink salmon (Oncorhynchus gorbuscha) in Power Creek near Cordova, Alaska in the summer; Alaska, United States of America