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

Male Sockeye Salmon (Oncorhynchus nerka) threatens another male by raising his formidable jaws with this tilted head posture in an Alaskan stream during early summer.

Male Sockeye Salmon (Oncorhynchus nerka) threatens another male by raising his formidable jaws with this tilted head posture in an Alaskan stream during early summer.

A Sockeye Salmon (Oncorhynchus nerka) spawning pair Underwater view in an Alaskan stream during the summer.

Sockeye Salmon (Oncorhynchus nerka) spawning pair positioned over a redd that is under construction in an Alaskan stream during early summer.

Sockeye Salmon (Oncorhynchus nerka) spawning pair positioned over a redd that is under construction in an Alaskan stream during early summer.

A Sockeye Salmon (Oncorhynchus nerka) spawning pair in an underwater view in an Alaskan stream during the summer.

A male Sockeye Salmon (Oncorhynchus nerka) holds a position high over a redd site as the female approaches from downstream in an Alaskan stream during early summer.

Sockeye Salmon (Oncorhynchus nerka) spawning pair positioned over a redd that is under construction in an Alaskan stream during early summer.

Three competing males surround a female Sockeye Salmon (Oncorhynchus nerka) in an Alaskan stream during late summer.

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

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

Sockeye Salmon (also known as Red Salmon, Oncorhynchus nerka) female excavating her redd while the male guards in an Alaskan stream during the summer; Alaska, United States of America

During September, Sockeye and Coho salmon (Oncorhynchus nerka and kisuch) intermingle during their spawning migration in an Alaskan stream; Alaska, United States of America

Female Coho Salmon, also known as Silver Salmon (Oncorhynchus kisutch) with alpha male contenders in an Alaskan stream during autumn; Alaska, United States of America

Alpha male Coho Salmon, also known as Silver Salmon (Oncorhynchus kisutch) maintains his position just ahead of a rival effectively blocking it's view of the female on his other side in an Alaskan stream during autumn; Alaska, United States of America

Mature Sockeye Salmon (Oncorhynchus nerka) male in an Alaskan stream during early summer.