Abundance & survival of the remnant Kootenai River white sturgeon population

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This report summarizes results of extensive monitoring and evaluation being conducted by the Kootenai Tribe of Idaho (KTOI), the Idaho Department of Fish and Game (IDFG), and the British Columbia Ministry of Forests, Lands and Natural Resource Operations (BCM). Thirty-five years of catch, marking, and recapture data for Kootenai white sturgeon were analyzed in order to estimate sampling rates, abundance, survival rates, recruitment, and trends for this population: 1). A total of 4,384 wild white sturgeon have been captured from the Kootenai River and Kootenay Lake during population assessments from 1978 through 2012. 2). No trends in annual catch per unit effort of sturgeon were apparent in angling or setline data from 1990-2012. 3). The wild sturgeon population currently averages approximately 160 cm fork length, and the large majority are 110 cm FL or longer. Fish size distributions are similar for river and lake samples. 4). Small numbers of wild juveniles (< 115 cm fork length) were caught with gillnets in most years, but an estimated abundance averaging just 72 fish from 1993 to 2011 demonstrates the continuing natural recruitment failure of this population. 5). The large majority of the wild sturgeon catch now consists of recaptures of tagged fish. Recaptures of tagged sturgeon comprise a greater percentage of the catch in the river (~80%) than in the lake (~60%) due to concentration of sampling effort in the river. 6). Analysis of acoustic telemetry data confirmed that individual tagged fish utilize the river and lake to varying degrees. 7). An open Jolly-Seber mark-recapture model that incorporates individual heterogeneity in capture probability and time-varying survival reduced biases of non-random sampling and appeared to better explain annual differences in recapture patterns. 8). This model estimated that the wild Kootenai adult sturgeon population declined from 2,968 (2,713–3,226) individuals in 1990 to 990 (733–1,375) in 2011. 9). Annual survival rate estimated by the mark-recapture analysis appear to have declined from around 97% prior to 2008 to 85% from 2007 to 2010. 10). The 2013 mark-recapture analysis produced substantially higher estimates of abundance than the previous analysis reported by Paragamian et al. (2005), which failed to fully consider underestimation bias resulting from non-random population mixing of fish tagged primarily in the river. 11). Analysis of hypothetical population data generated using an individual-based model demonstrated the sensitivity of open Jolly-Seber models to non-random tag mixing and sampling. 12). Projected future abundance trends of wild sturgeon varied substantially depending on which model was used to determine current abundance and survival.

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ELECTRONIC FILE - Zoology

SWAP (2/19/2016) citation:
Beamesderfer R, Garrison T, Anders P. 2014. Abundance & survival of the remnant Kootenai River white sturgeon population. [publisher unknown]. 46 p. Report prepared for the Kootenai Tribe of Idaho. [accessed 2016 Jan 28]. http://www.fishsciences.net/reports/download_report.php?rid=6840.

Author affiliations, respectively, if needed: R2 Resource Consultants, Vancouver, WA; Cramer Fish Sciences, Gresham, OR; Cramer Fish Sciences and University of Idaho, Moscow, ID. The document has, from left to right along the bottom of the cover page, logos for R2 and Cramer Fish Sciences.