Kootenai National Forest

Kootenai National Forest
31374 US Highway 2
Libby, MT 59923-3022
(406) 293-6211
All Forest Offices

Fisheries Management

Fish illustrations are from the
Montana Fish, Wildlife & Parks
guide and were painted by Glenn West

Burbot

The burbot Lota lota, locally referred to as the "ling" or "ling cod", is the only freshwater member of the cod family. Burbot are typically associated with larger streams or rivers and deep, cold lakes or reservoirs. Historically, they inhabited the mainstem Kootenai River and a few of its tributaries. Recent research below Libby Dam estimates the population in that area to be near 1,000 individuals (range 680-1,700).

Although spawning has been confirmed below Libby Dam, it is not known if burbot spawn below Kootenai Falls in Montana.

Burbot may also occur in the Yaak River below Yaak Falls. Distribution of burbot is limited to the Kootenai River on the Kootenai and Idaho Panhandle National Forests Burbot are a cold-water, bottom-dwelling species. Burbot are eel-like with marbled body coloration from dark olive to brown on the back contrasted with brown or black; the sides are lighter than the back; and the belly is yellowish white (Simpson and Wallace 1982). Burbot have a distinguishing single slender barbel on the chin. In the lower Kootenai River, burbot can weigh up to 10 lb and live up to 15 years.

Burbot that occur in the Kootenai River basin exhibit three life history strategies in several potentially isolated groups. The burbot that constitute the lower Kootenai River population spend a portion of their life in the South Arm of Kootenay Lake, and then migrate up the Kootenai River during the winter months to spawn in the mainstem river or tributary streams in British Columbia or Idaho (an adfluvial life form, i.e., one that migrates from lake to river and tributary streams for spawning). Kootenai Falls in Montana, present for approximately 10,000 years, physically isolates this population of burbot from the population that occurs above the falls (Paragamian et al. 1999). Burbot above the falls are believed to spend their entire lives in the river system (a fluvial life form, i.e., one that spends its entire life in the river or migrates from river to tributary streams for spawning). A burbot population also exists in Lake Koocanusa, a reservoir formed when Libby Dam was constructed near Libby, Montana, in the early 1970s.

Under natural conditions, burbot in the Kootenai River basin spawn under ice during the winter months in water temperatures below 4°C (39°F) (Simpson and Wallace 1982). Spawning commences in early February and lasts 2 to 3 weeks.

Most information suggests that river spawning burbot prefer low velocity areas in main channels or in side channels behind deposition bars, with the preferred substrate consisting of fine gravel, sand, or silt (Fabricius 1954 in McPhail and Paragamian, in draft; McPail and Paragamian, in draft). Spawning is also known to occur in small tributary streams and is generally believed to take place at night (Simpson and Wallace 1982; McPhail and Paragamian, in draft).

Female burbot are larger than males and, depending on their size, may produce between 50,000 and 1,500,000 eggs (Simpson and Wallace 1982). Male burbot typically reach sexual maturity in 3 to 4 years, with females maturing in 4 to 5 years (BRS, in draft). During spawning, burbot typically collect in a large mass referred to as a spawning ball, with one or more females in the center surrounded by many males (Simpson and Wallace 1982; McPhail and Paragamian, in draft). There is no site preparation during spawning, and eggs are broadcast into the water column well above the substrate. The eggs are semi-buoyant and eventually settle into cracks in the substrate. Newly hatched burbot drift passively in open water until they develop the ability to swim (McPhail and Paragamian, in draft). Young burbot initially select shoreline areas among rocks and debris for feeding and habitat security.

Burbot prefer cold water and, during summer months, move to the hypolimnion (lower zone of a thermally stratified lake) areas of lakes or deep-water pools of large rivers (Simpson and Wallace 1982). Feeding is mostly done at night, with adult burbot feeding almost exclusively on fish. Young burbot feed on a variety of aquatic organisms, such as insects, amphipods, snails, and small fish (Simpson and Wallace 1982). Burbot are most active in the winter when they move great distances to spawn, but are rather sedentary during the non-spawning seasons.

The lower Kootenai River once supported a significant number of burbot and provided an important winter fishery to the region. Although declines in burbot numbers in Idaho and British Columbia had been documented as early as 1959, they were still considered relatively stable through the 1960s. Despite fishery regulations implemented in the 1970s, the burbot fisheries in the Idaho and British Columbia portion of the basin collapsed after the construction of Libby Dam in 1972. Only 145 adult burbot have been captured in the Kootenai River in Idaho and British Columbia since 1993 (Paragamian et al. 1999). Spawning was known to occur in many tributary streams in Idaho and likely occurred in the river (BRS, in draft). However, recent studies reveal scant evidence of burbot reproduction in Idaho, as no larval fish and only one juvenile fish have been captured since 1993 (Paragamian and Whitman 1999). Currently, the only tributary known to support spawning burbot is the Goat River, which is just north of the Idaho border in British Columbia (Paragamian 1995a; Paragamian, in draft).

Prior to the collapse of the lower Kootenai River burbot population in the 1970s, anglers reported catching more than 40 burbot a night during the winter using setlines. The estimated annual harvest for the sport and commercial fishery was in the tens of thousands of kilograms or several thousand fish annually (BRS, in draft; Paragamian, pers. comm. 2000). However, the annual harvest of burbot between 1979 and 1983 was estimated at about 250 fish. Concurrent with the decline of burbot in Idaho was the decline in British Columbia and, despite numerous harvest regulations implemented in both Idaho and British Columbia, burbot continued to decline and both fisheries were closed in the 1990s.

Declines in lower Kootenai River burbot appear to be most strongly associated with habitat modification resulting from the construction and operation of Libby Dam (Paragamian 1993; Paragamian et al. 1999). Temperature and flow changes that alter spawning patterns and poor fry survival due to a reduction in food productivity in the river are believed to be the primary threats to burbot (Paragamian 1993; Paragamian and Whitman 1998; Paragamian et al. 1999).

In addition to flow change, winter water temperature has increased by 2 to 3°C (4 to 5°F) since the construction of Libby Dam. This temperature increase is believed to influence the activity level and location of burbot during the pre-spawn migration. Prior to the construction of Libby Dam, many portions of the lower Kootenai River would freeze allowing burbot to spawn under ice in water temperatures between 1 and 3°C (34 and 37°F) (Becker 1983 in Paragamian 1995a). Lower Kootenai River temperatures are now 4 to 5°C (39 to 41°F) during the winter months and many sections no longer freeze over (Paragamian 1995a).

The decline in the productivity of the Kootenai River and in Kootenay Lake following the construction of Libby Dam may also be linked to the decline of burbot. Sediment nutrients settle behind Libby Dam in Lake Koocanusa and reduce the nutrient loading to the river. Analyses of macrozooplankton in the lower Kootenai River indicated that there is a scarcity of important foods such as Daphnia, Diaphanosoma, and Cyclops (Paragamian 1995b).