Quantifying long-term population growth rates of threatened bull trout: challenges, lessons learned, and opportunities.

Temporal symmetry models (TSM) represent advances in the analytical application of mark-recapture data to population status assessments. For a population of char, we employed 10 years of active and passive mark-recapture data to quantify population growth rates using different data sources and analytical approaches. Estimates of adult population growth rate were 1.01 (95% confidence interval = 0.84-1.20) using a temporal symmetry model ( λTSM), 0.96 (0.68-1.34) based on logistic regressions of annual snorkel data ( λA), and 0.92 (0.77-1.11) from redd counts ( λR). Top-performing TSMs included an increasing time trend in recruitment ( f) and changes in capture probability ( p). There was only a 1% chance the population decreased ≥50%, and a 10% chance it decreased ≥30% ( λMCMC; based on Bayesian Markov chain Monte Carlo procedure). Size structure was stable; however, the adult population was dominated by small adults, and over the study period there was a decline in the contribution of large adults to total biomass. Juvenile condition decreased with increasing adult densities. Utilization of these different information sources provided a robust weight-of-evidence approach to identifying population status and potential mechanisms driving changes in population growth rates. [ABSTRACT FROM AUTHOR]