Bull Trout Distribution and Abundance in the Waters on and Bordering the Warm Springs Reservation : 2002 Annual Report.

Brun, Christopher V. ; Dodson, Rebekah

United States. Bonneville Power Administration.

关键词: Bull Trout - Oregon - Warm Springs Indian Reservation - Counting;    Abundance;    Adults;    15 Geothermal Energy;    Juveniles;   

DOI  :  10.2172/815123
RP-ID  :  DOE/BP-00006212-1
RP-ID  :  NONE
RP-ID  :  815123

美国|英语

来源: UNT Digital Library

【 摘 要 】

The range of bull trout (Salvelinus confluentus) in the Deschutes River basin has decreased from historic levels due to many factors including dam construction, habitat degradation, brook trout introduction and eradication efforts. While the bull trout population appears to be healthy in the Metolius River-Lake Billy Chinook system they have been largely extirpated from the upper Deschutes River (Buchanan et al. 1997). Little was known about bull trout in the lower Deschutes basin until BPA funded project No.9405400 began during 1998. In this progress report we describe the findings to date from this multi-year study aimed at determining the life history, habitat needs and limiting factors of bull trout in the lower Deschutes subbasin. Juvenile bull trout and brook trout (Salvelinus fontinalis) relative abundance has been assessed in the Warm Springs River and Shitike Creek since 1999. In the Warm Springs R. the relative densities of juvenile bull trout and brook trout were .003 fish/m{sup 2} and .001 fish/m{sup 2} respectively during 2002. These densities were the lowest recorded in the Warm Springs River during the period of study. In Shitike Cr. the relative densities of juvenile bull trout and brook trout were .025 fish/m{sup 2} and .01 fish/m{sup 2} respectively during 2002. The utility of using index reaches to monitor trends in juvenile bull trout and brook trout relative abundance in the Warm Springs R. has been assessed since 1999. During 2002 the mean relative densities of juvenile bull trout within the 2.4 km study area was higher than what was observed in four index reaches. However, the mean relative densities of brook trout was slightly higher in the index reaches than what was observed in the 2.4 km study area. Habitat use by both juvenile bull trout and brook trout was determined in the Warm Springs R. Juvenile bull trout and brook trout were most abundant in pools and glides. However pools and glides comprised less than 20% of the available habitat in the study area during 2002. Multiple-pass spawning ground surveys were conducted during late August through October in the Warm Springs R. and Shitike Cr. during 2002. One-hundred and thirteen (113) redds were enumerated in the Warm Springs R. and 204 redds were found in Shitike Cr. The number of redds enumerated in both the Warm Springs R. and Shitike Cr. were the most redds observed since surveys began in 1998. Spatial and temporal distribution in spawning within the Warm Springs R. and Shitike Cr. is discussed. Juvenile emigration has been monitored in Shitike Creek since 1996. A total of 312 juveniles were estimated to have emigrated from Shitike Cr. during the spring, 2002. Adult escapement was monitored in the Warm Springs R. and Shitike Cr. Thirty adults were recorded at the Warm Springs National Fish Hatchery weir during 2002. This was the highest number of spawning adults recorded to date. A weir equipped with an underwater video camera near the spawning grounds was operated in the Warm Springs R. Thirty-one adults were recorded at the weir in day counts. The adult trap in Shitike Cr. was unsuccessful in capturing adult bull trout during 2002 due to damage from a spring high water event. Thermographs were placed throughout Warm Springs R. and Shitike Cr. to monitor water temperatures during bull trout migration, holding and spawning/rearing periods. During 1999-2002 water temperatures ranged from 11.8-15.4 C near the mouths during adult migration; 11.4-14.6 C during pre-spawning holding; and 6.5-8.4 C during adult spawning and juvenile rearing.