Stocking for rehabilitation of burbot in the Kootenai River, Idaho, USA and British Columbia, Canada

Abstract

Summary The burbot Lota lota is widespread globally, but the population in the Kootenai River, Idaho and British Columbia, Canada is at risk of extirpation because of habitat changes caused by operation of Libby Dam in Montana, 100 km upstream of the border with Idaho. We developed an age-structured simulation model to estimate the number of age-0 burbot (fall fingerlings) to stock annually to rebuild the population in the Kootenai River. We found with the estimated annual survival of about 38% that 110 000–900 000 age-0 burbot per year will need to be stocked to rebuild the burbot population in the Kootenai River in 25 years, depending on the rehabilitation goal, either 5500 age-4 burbot and older as an interim goal or 17 000 age-4 and older burbot as an ultimate goal (longer than 250 mm). If survival is higher at 61% then the stocking numbers could range from 12 000 to 35 000 age-0 fingerlings per year. After stocked burbot in the population reach age 4, discharge from Libby Dam must be regulated to provide suitable temperatures and flows during the burbot pre-spawning and spawning periods, to enable the population to reproduce and return to self-sustaining status. Our findings will serve as an example for similar efforts to restore depleted burbot populations elsewhere in the world.