A sockeye salmon (Oncorhynchus nerka) in a small breeding stream in southwestern Alaska.

A sockeye salmon (Oncorhynchus nerka) in a small breeding stream in southwestern Alaska. Adult sockeye lay their eggs in the gravel of streams, rivers, or along the beaches of lakes in late summer and fall, and the fry emerge the following spring. Juveniles typically spend 1-2 years in lakes prior to migrating to the North Pacific Ocean where they spend another 1–3 years feeding and growing. Afterwards, salmon migrate back to freshwater, complete their maturation, and then make the final stage of their journey, from the lake to their natal sites where they breed and die. Large-bodied salmon are particularly vulnerable to lake-level-induced stranding mortality before they reach the breeding grounds. Salmon breeding in smaller creeks tend to be smaller, younger and more streamlined than conspecifics from neighboring populations. This photograph originally appeared on the cover of Ecology (88:10) in October of 2007.