A Synthesis of Kootenai River Burbot Stock History and Future Management Goals

Abstract

In Idaho, Burbot Lota lota are endemic only to the Kootenai River, where they once provided an important winter fishery to the indigenous people and European settlers. This fishery and that of Kootenay Lake in British Columbia may have been the most robust Burbot fisheries in North America. However, the fishery in Idaho rapidly declined after the construction of Libby Dam by the U.S. Army Corps of Engineers in 1972, and it closed in 1992. Concomitant to the collapse in Idaho was the collapse of the Burbot fishery in Kootenay Lake and the Kootenay River. The operation of Libby Dam for hydroelectric power generation and flood control created major changes in the river's nutrient concentration, temperature, and seasonal discharge, particularly during the winter when Burbot spawn. Libby Dam operations were implicated as the major limiting factor to Burbot recruitment, giving rise to higher winter temperatures and widely fluctuating flows. Because the Burbot in the Kootenai River are at risk of demographic extinction, a conservation strategy was prepared to outline the measures necessary to rehabilitate the Burbot population to a self-sustaining level. The strategy indicated that operational discharge changes at Libby Dam are required during winter to provide suitable temperature and discharge conditions for Burbot migration and spawning. Studies recommend that the discharge at Bonners Ferry average 176 m 3 /s for a minimum of 90 d (midNovember through mid-February). Furthermore, preferred Burbot water temperatures of about 6 • C are necessary for migration and cooler temperatures of 1-4 • C for spawning. With each passing year, Burbot stock limitations increasingly constrain rehabilitation. Thus, coordination of intensive culture, extensive rearing, and pen rearing among the Kootenai Tribe of Idaho, the British Columbia Ministry of Environment, the University of Idaho's Aquatic Research Institute, and the Idaho Department of Fish and Game is important for restoration.

Assessment of burbot Lota lota (L. 1758) population sustainability in central European reservoirs

“…More years are needed to calculate survival rates in order to get reliable estimates, since short‐term assessment is a limitation of this study. Successful restoration of a L. lota population was described for Kootenai River, Idaho, U.S.A. (Hardy & Paragamian, ) and the Netherlands (Bosveld et al, ) where hundreds of thousands of larger juvenile L. lota were stocked. Lota lota in our reservoirs were stocked in late spring at sizes up to 50 mm L T .…”

Burbot and large hydropower in North America: benefits, threats and research needs for mitigation

“…Successful spawning was only observed when drought conditions reduced winter discharge to an average of 174 m s −1 (Paragamian et al . ; Hardy & Paragamian ). Hydropeaking or ramping, where turbines are turned on or off in relation to diel and even hourly fluctuations in demand for electricity, results in highly variable flows and current velocity downstream of turbines; as a weak swimmer (Jones et al .…”

“…). In addition to acting as a physiological requirement for successful spawning and egg incubation, winter temperatures below 6 °C, have also been shown to act as an important trigger for burbot spawning migrations (Paragamian & Wakkinen ; Hardy & Paragamian ). Furthermore, the slow rate of cooling associated with reservoir thermal mass may have an impact on burbot reproductive success, as Zarski et al .…”

“…; Fig. ); and hydropower facilities, which are concentrated in this region, have been implicated in the decline (Hardy & Paragamian ).…”

Ecology, culture, and management of Burbot: an introduction

“…These difficulties sometimes hamper restoring imperiled populations in some systems (e.g., Hardy & Paragamian, 2013).…”