Bull trout population assessment in northeastern Oregon: a template for recovery planning Progress Report for 2011

There are critical gaps in information that potentially limit our ability to effectively

manage bull trout and ensure their continued persistence (Porter and Marmorek 2005;

Al-Chokhachy et al. 2008). These gaps include quantification of population abundance

and trend for all but a few populations, estimates of larval and juvenile survival rates,

estimates of dispersal rates between populations, and life-history-specific information,

such as the contribution of migratory versus resident fish to overall population growth

and persistence. Our research seeks to address some of these knowledge gaps

through long-term monitoring of a relatively large bull trout population in the South Fork

Walla Walla River (SFWW). We provide essential information on abundance, trend,

vital rates, habitat needs, and information on the potential for improving survival at one

or more life stages. In addition, we gather information related to population structure

(e.g., age, life history, and genetic components) and provide a template against which

different strategies for monitoring can be evaluated in terms of accuracy, precision,

cost/effort, and limiting factors. Our goal is to provide data and conservation

assessment tools to aid in the efforts of the US Fish and Wildlife Service, to determine

the necessary course of action for the recovery of bull trout populations throughout the

study region and the rest of the species’ range. The project was initiated in 2002 and

has continued through 2011 (10 years). To meet our goals, each year we have

developed and implemented a comprehensive mark- recapture program using two tag

types, multiple capture techniques (both passive and active) and systematic sampling of

two large study areas (SFWW and North Fork Umatilla rivers) with a high degree of

effort. The year 2008 marked the fifth and final year of sampling and study in the North

Fork Umatilla River while sampling has continued in the SFWW. 2008 marked the last

year of field sampling by Utah State University.

The efforts of this project have been part of a completed PhD dissertation (Al-

Chokhachy 2006) and MS thesis (Homel 2007) and are currently part of an on-going

PhD dissertation (Bowerman, in preparation) and MS thesis research (Newlon, in

progress) conducted through Utah State University. Results and syntheses of different

components of the project are available in previous annual reports (Budy et al. 2003,

2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, and herein) as well as in the peerreviewed

manuscripts: Al-Chokhachy et al. 2005; Al-Chokhachy and Budy 2007; Homel

and Budy 2008; Homel et al. 2008; Al- Chokhachy and Budy 2008; and Al-Chokhachy

et al. 2009; and Al-Chokhachy et al. 2010, Bowerman and Budy, in review.