Historically, several streams supported substantial runs of Chinook salmon within the boundaries of the 1855 Treaty between the United States and the Nez Perce Tribe. Severe declines in abundance and distribution of Snake River Spring/Summer Chinook salmon led to their listing as threatened under the Endangered Species Act in 1992. In fact, only 11 Chinook salmon redds were found in the Lostine River during extensive spawning ground surveys in 1995.
Efforts to restore Chinook salmon in the Lostine River and other Grande Ronde River tributaries began in 1994 as a joint effort between the Nez Perce Tribe (NPT), the Confederated Tribes of the Umatilla Indian Reservation, Oregon Department of Fish and Wildlife, and the United States Fish and Wildlife Service. To return populations to self-sustaining levels, some populations were supplemented with hatchery-reared fish derived from endemic broodstock. The Nez Perce Tribe started collecting natural-origin Chinook salmon parr for a captive broodstock program in 1995 and initiated a conventional program in 1997. These two strategies formed the basis of Chinook supplementation efforts in the Lostine River.
Hatchery-origin juvenile Chinook salmon were first released into the Lostine in 1999, and subsequently, the first hatchery-origin adults returned to the Lostine to spawn in 2001. The captive broodstock and conventional hatchery program have jointly contributed to annual releases of about 250,000 smolts in most years. The captive program was phased out as the conventional program increased production capable of reaching the annual release goal of 250,000 smolts. The captive program last contributed smolts in the 2011 release. Smolt-to-adult return rates for hatchery-origin Chinook salmon have been higher than originally planned for the supplementation program. In 2009, the population reached the mid-term management goal of returning 500 adult natural-origin Chinook salmon and has exceeded that mark in all but one year from 2009-2015.
This project assesses population metrics designed to inform adaptive management of Chinook salmon, with a focus on evaluating the risks and benefits of hatchery supplementation. Specifically, we compare and contrast a suite of abundance, productivity, and life history characteristics for both hatchery- and natural-origin juveniles and adults.