Grande Ronde Basin Spring Chinook Salmon Captive Broodstock Program, 1995-2002 Summary Report.

Hoffnagle, Timothy ; Carmichael, Richard ; Noll, William

United States. Bonneville Power Administration.

关键词: Fragmentation;    Adults;    Genetics;    Habitat;    Salmon;   

DOI  :  10.2172/962673
RP-ID  :  DOE/BP-00004023-1
RP-ID  :  4023
RP-ID  :  962673

美国|英语

来源: UNT Digital Library

【 摘 要 】

The Grande Ronde Basin once supported large runs of chinook salmon Oncorhynchus tshawytscha and estimated peak escapements in excess of 10,000 occurred as recently as the late 1950's (U.S. Army Corps of Engineers 1975). Natural escapement declines in the Grande Ronde Basin have been severe and parallel those of other Snake River populations. Reduced productivity has primarily been attributed to increased mortality associated with downstream and upstream migration past eight dams and reservoirs in the Snake and Columbia rivers. Reduced spawner numbers, combined with human manipulation of previously important spawning and rearing habitat in the Grande Ronde Basin, have resulted in decreased spawning distribution and population fragmentation of chinook salmon in the Grande Ronde Basin (Figure 1; Table 1). Escapement of spring/summer chinook salmon in the Snake River basin included 1,799 adults in 1995, less than half of the previous record low of 3,913 adults in 1994. Catherine Creek, Grande Ronde River and Lostine River were historically three of the most productive populations in the Grande Ronde Basin (Carmichael and Boyce 1986). However, productivity of these populations has been poor for recent brood years. Escapement (based on total redd counts) in Catherine Creek and Grande Ronde and Lostine rivers dropped to alarmingly low levels in 1994 and 1995. A total of 11, 3 and 16 redds were observed in 1994 in Catherine Creek, upper Grande Ronde River and Lostine River, respectively, and 14, 6 and 11 redds were observed in those same streams in 1995. In contrast, the maximum number of redds observed in the past was 505 in Catherine Creek (1971), 304 in the Grande Ronde River (1968) and 261 in 1956 in the Lostine River (Tranquilli et al 2003). Redd counts for index count areas (a standardized portion of the total stream) have also decreased dramatically for most Grande Ronde Basin streams from 1964-2002, dropping to as low as 37 redds in the 119.5 km in the index survey areas in 1995 from as high as 1,205 redds in the same area in 1969 (Table 1). All streams reached low points (0-6 redds in the index areas) in the 1990's, except those in which no redds were found for several years and surveys were discontinued, such as Spring, Sheep and Indian creeks which had a total of 109 redds in 1969. The Minam and Wenaha rivers are tributaries of the Grande Ronde River located primarily in wilderness areas. Chinook salmon numbers in these two streams (based on redd counts) also decreased dramatically beginning in the early 1970's (Table 1). Since then there have been a few years of increasing numbers of redds but counts have generally been 25-40% of the number seen in the 1960's. No hatchery fish have been released into either of these streams and we monitor them during spawning ground surveys for the presence of hatchery strays. These populations will be used as a type of control for evaluating our supplementation efforts in Catherine Creek, upper Grande Ronde River and Lostine River. In this way, we can attempt to filter out the effects of downstream variables, over which we have no control, when we interpret the results of the captive broodstock program as the F1 and F2 generations spawn and complete their life cycles in the wild. The Grande Ronde Basin Captive Broodstock Program was initiated because these chinook salmon populations had reached critical levels where dramatic and unprecedented efforts were needed to prevent extinction and preserve any future options for use of endemic fish for artificial propagation programs for recovery and mitigation. This program was designed to quickly increase numbers of returning adults, while maintaining the genetic integrity of each endemic population.