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

Abstract

SummaryThe 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 agestructured 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.

A novel experiment of rearing burbot larvae in cages

“…The practicality of cage rearing burbot cannot be fully addressed by this study alone but a limitation is that without supplemental feeding only low numbers of burbot could be reared in cages of 30–40 m −3 . Far more cages than the five tested in this study would be required to rear sufficient numbers of burbot needed for burbot rehabilitation in the Kootenai River of 110 000–900 000 annually (Paragamian and Hansen, 2011).…”

“…In the Kootenai River of Idaho, USA the burbot population has been in decline since the 1970s (Paragamian et al., 2000) and is on the brink of extirpation (Paragamian et al., 2008). The primary reason was due to habitat changes linked to operations of the Libby Dam in Montana, USA (Paragamian, 2000; Paragamian and Wakkinen, 2008).…”

“…The primary reason was due to habitat changes linked to operations of the Libby Dam in Montana, USA (Paragamian, 2000; Paragamian and Wakkinen, 2008). Any expectations that this population can recover within the next decade are unreasonable even with the most suitable habitat changes in winter discharge, winter temperatures, and improved primary production (Paragamian et al., 2008). Thus, it is of crucial importance that remedial measures to improve this stock’s abundance begin immediately not ignoring the importance of habitat changes.…”

Evaluation of methods for the collection and fertilization of burbot eggs from a wild stock for conservation aquaculture operations

“…In the Kootenay River, British Columbia (BC), Canada (spelled Kootenai in Idaho and Montana, USA), burbot ( Lota lota maculosa ) numbers have diminished to near extirpation (Paragamian et al., 2008) due to factors including physical changes to the river and overfishing (Paragamian et al., 2000; Kootenai Valley Resource Initiative (KVRI) Burbot Committee (2005); Stapanian et al., 2010). Both the lake and river supported large sport and commercial harvests of burbot as late as the 1970s, until severe declines resulted in the eventual closure of these fisheries (Paragamian et al., 2000; Ahrens and Korman, 2002).…”

“…Recent capture and underwater video work suggests the historic population on Kootenay Lake at Balfour, BC has been functionally extirpated (Baxter et al., 2002a,b; Neufeld and Spence, 2004; Neufeld, 2005) and the most recent River population estimate in BC and Idaho was 50 burbot in 2004 (including tributary populations). At an estimated annual decline in population abundance of 14%, extirpation will likely occur in the next decade (Paragamian et al., 2008). Declines such as these in burbot populations are common and resulting conservation efforts are underway worldwide (Arndt and Hutchinson, 2000; Harzevili et al., 2003; Dillen et al., 2008; Ireland and Perry, 2008; Jensen et al., 2008a; Vught et al., 2008; Worthington et al., 2010).…”