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

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

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

Underwater view of caddisfly larvea consuming a sockeye salmon carcass in Power Creek near Cordova, Alaska in the summer; Alaska, United States of America

Underwater view of a coho salmon (Oncorhynchus kisutch) spawning in Power Creek near Cordova, Alaska in the autumn; Alaska, United States of America

Male Sockeye Salmon (Oncorhynchus nerka) threatens another male by raising his formidable jaws with this tilted head posture, underwater view in an Alaskan stream during early summer; Cordova, 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 in an Alaskan stream during the summer. The small male is a jack; Alaska, United States of America

Mature male Sockeye Salmon, also known as Red Salmon (Oncorhynchus nerka) in an Alaskan stream during the summer, 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

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

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

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

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

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

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

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

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