In 1979, pink salmon (Oncorhynchus gorbuscha) completed expansion of their range from Lake Superior into each of the other four Great Lakes. Record numbers of pink salmon were observed during the 1979 spawning migrations into Lake Superior tributaries. Although the species was introduced into Lake Superior 24 years ago, movement into the other lakes was slow and until 1979 the known range was restricted to northern portions of Lakes Michigan and Huron. Pink salmon remain the only self-sustaining species of salmon in the Great Lakes. The development of spawning populations in both even- and odd-numbered years and other adaptive biological features may have contributed to their success.