Kootenai River Fisheries Investigation; Stock Status of Burbot, 2003-2004 Annual Report.

Abstract

The main objective of this investigation was to monitor movement and spawning activity of burbot Lota lota in the Kootenai River, Idaho and British Columbia, Canada during the winter of 2003-2004. Due to low precipitation and snow pack, as well as low levels of Lake Koocanusa, the U.S. Army Corps of Engineers refrained from releasing discharges >113 m{sup 3}/s from Libby Dam for most of the winter. This situation provided suitable conditions for burbot migration and spawning in the mainstem river. Hoop nets captured 19 burbot, which ranged from 447 mm to 760 mm TL (mean = 630 mm) and weighed from 420 g to 4,032 g (mean = 1,937 g) with a mean W{sub r} of 99. One burbot (burbot 214) was captured for the fifth time since its first capture in 2000, and each capture was near Ambush Rock (rkm 244.4-244.8). Eleven burbot were tagged with five-month duration external sonic transmitters, and a 12th burbot, tagged with a 14-month transmitter, has been monitored since 2001. During the post-spawn period, three sonic-tagged burbot exhibited downstream and sedentary movement patterns, while five remained at Ambush Rock. Concentrations of tagged burbot near Ambush Rock (rkm 244.5) during January and February 2004more » (eight tagged fish) may suggest that this area is critical spawning habitat. The appearance of burbot at Ambush Rock during the spawning period and upstream movements of tagged fish (PIT and sonic tagged) in previous years during the low discharges help validate results suggesting that discharges <113 m{sup 3}/s will permit burbot migration and may increase spawning habitat. Though it seems apparent that the Ambush Rock area is an important burbot spawning ground, no adult burbot were recaptured after the spawning period and no burbot larva were caught, despite considerable sampling efforts during the winter of 2003-2004.« less