Abstract
White Sturgeon ¬Acipencer transmontanus is recreationally and economically important throughout its distribution. In Idaho, managers have increased opportunity for anglers through a White Sturgeon stocking program where Idaho Department of Fish and Game has established a population outside the native distribution of the species. Since 1990, around 7,650 White Sturgeon have been stocked in the upper Snake River (i.e., Minidoka Dam to Upper Idaho Falls Dam). Increased participation in the fishery has prompted a thorough investigation of White Sturgeon population dynamics in the upper Snake River. The objectives of this study were to investigate the population dynamics of White Sturgeon in the upper Snake River and develop an age-structured population model to evaluate potential stocking and harvest scenarios (e.g., slot limits, annual quotas). Sampling took place from June–October, 2022, and June–August, 2023, using angling (i.e., rod-and-reel) and setlines. In total, 340 individual White Sturgeon were captured throughout the study area with 181 recapture events. Individuals varied in length from 54 to 205 cm fork length (FL) and the mean relative weight for captures was 105.2 (SD = 14.4) suggesting relatively high body condition. Capture histories from 261 known-age White Sturgeon informed age and growth analysis and an evaluation of movement trends. Age varied from 2–25 years and White Sturgeon moved an average of 8.1 rkm (SD = 23.5) downstream from stocking locations. Estimated abundance of White Sturgeon at the tailwaters of American Falls Dam was 428 (95% CI = 403–463) fish. The abundance estimate was used to inform a total abundance estimate of 887 (95% CI = 835–960) White Sturgeon in the study area. Apparent annual survival was 0.79 (95% CI = 0.64–0.89). A population model was parameterized using information on the dynamics of White Sturgeon in the upper Snake River. The model was used to estimate the effects varying stocking rates and harvest scenarios (i.e., harvest slot of 76–122 cm FL and annual quotas of 0–25 White Sturgeon harvested) on the population. A stocking rate of 285 age-2 White Sturgeon per year was necessary to maintain current abundance. For every five fish harvested per year, abundance would decrease by about 2.2% over 20 years. Information from this investigation provides important insight on the ecology of White Sturgeon and provides guidance for the management of the White Sturgeon fishery in the upper Snake River.