Fisheries Management

A Changing Lake

Dramatic Changes

Since the last co-management plan was written in 1989, kokanee salmon have disappeared from Flathead Lake despite a 5-year effort to recover them. Mysis shrimp, first noted in Flathead Lake in 1981, strip zooplankton from the upper waters of the lake and serve as food for deep water fish such as lake trout and lake whitefish. Lake trout have increased in numbers and now make up most of the recreational fishery. Lake whitefish are also very numerous. Native species such as bull trout and westslope cutthroat trout have declined. With the establishment of Mysis and growth of the lake trout population, we have increased angling limits on lake trout and decreased limits on native trout. These limit changes illustrate the strategy followed by Montana Fish, Wildlife & Parks (FWP) and the Confederated Salish and Kootenai Tribes (CSKT) to address increasing numbers of nonnative fish and decreasing numbers of native fish. The lake’s food web has been unstable, which means future management needs to be flexible and based on “adaptive management”. Adaptive management emphasizes the application of new knowledge and techniques as they become available. Through adaptive management, actions can be adjusted as new information comes to light. 

The Confederated Salish Kootenai Tribe completed an EIS process to benefit native trout.

Flathead Lake and River Fisheries Co-Management Plan

This analysis replaces a “Record of Decision” (ROD) that typically follows the completion of an Environmental Impact Statement. The BIA, trust agency for the CSKT, deemed a ROD unnecessary because BIA had previously granted their authority for CSKT to suppress lake trout when giving approval to the Kerr Dam mitigation program. In addition to replacing the Record of Decision, this plan establishes the annual process that the Confederated Salish and Kootenai Tribes will follow to implement the direction of the Co-Management Plan. Click on the button below to download a copy of the plan.

Summary of Activities

This report summarizes results of the fourth year of work conducted under the direction of the Implementation Plan for Lake Trout Suppression in Flathead Lake (2014) by the Confederated Salish and Kootenai Tribes (CSKT). The Implementation Plan is the culmination of a lengthy and often contentious process in management of the fishery of Flathead Lake. It was preceded by the Flathead Lake and River Fisheries CoManagement Plan (CoPlan) that was adopted in 2000 by CSKT and Montana Fish Wildlife and Parks (MFWP). The goals of the CoPlan are to: (1) “Increase and protect native trout populations”, and (2) “Balance tradeoffs between native species conservation and nonnative species reduction to maintain a viable recreational/subsistence fishery”.

Benefit Native Species by Reducing the Abundance of Lake Trout

The FEIS analyzes the environmental consequences of a proposal to benefit native fish populations by reducing the abundance of non-native lake trout in Flathead Lake. Because of the migratory nature of fish in the system, areas north or upstream of the lake—specifically, the Flathead River and its tributaries— are included in the analysis. The proposed action would use a combination of fisheries population management tools, including angling and netting, to reduce the population of lake trout. The need for the project is based on over two decades of continuous and cooperative regional research, management, and planning by Tribal, State, and Federal agencies.

The research, joint planning efforts, and decision-making processes are recorded in our guidance documents, which include: the Flathead Lake and River Fisheries Co-Management Plan (2000), the Restoration Plan for Bull Trout in the Clark Fork River Basin and Kootenai River Basin (2000), the Cutthroat Memorandum of Understanding and Conservation Agreement (2007), the Flathead Subbasin Plan, Part III (2004), the CSKT Comprehensive Resources Plan (1996), and the CSKT Fisheries Management Plan (1993).

Lake Trout Biology

Mack Days helps the ecological balance of Flathead Lake by thinning the mackinaw (also called lake trout) population. The  event succeeded in it’s first event (2002 Fall) in stimulating the harvest of lake trout and in educating people about the Flathead Lake Fisheries Management Plan. Let’s keep a good thing going. Anglers help manage the lake by harvesting over abundant lake trout. Learn about the biology below by clicking on the buttons. You can also read an interesting blog spot about the history of lake trout in Flathead Lake by clicking here.

Basic Identification and Montana Distribution

Also called the Mackinaw Trout, the lake trout is found mostly in the Fort Peck area with some occurrence in the western part of the state. The lake trout is a slate gray to bluish fish with numerous light colored spots. These spots can range in color from white to a pale yellow, but are never red or orange. However fins may have traces of orange, white leading edge is often present on fins as well. Lake trout may have pale wavy lines on their back.

  • Average Size: 14″-20″
  • Habitat: Deep, cold lakes and reservoirs.
  • Montana Record Catch: 42lbs 11.8 oz, 42.5″ long & 31.5″ around
  • Caught in Flathead Lake in 2004 by Ruth Barber.

Tail: Deeply forked (center rays less than half length of longest rays).
Dorsal Fin: Without spots or sometimes with light-colored oval markings.
Body: With white or cream-colored spots (never pink or red) on darker background.
Appearance: Overall gray or nearly black/white coloration, sometimes with yellow tinge on fins.

Physical Characteristics

Lake trout are the largest trout native to North America. The largest lake trout on record weighed 46.3 kg (102 lb), which was caught by the commercial fishery at Lake Athabasca, Saskatchewan in 1961. The angling record contains a specimen weighing 32.8 kg (72.25 lb), caught in Great Bear Lake, Northwest Territories, in 1995. In Nova Scotia, the average lake trout caught is usually less than 2.0 kg (4.4 lb). A lake trout weighing 8.6 kg (19 lb) and measuring 81.3 cm (32 inches) was caught in Sherbrooke Lake, Nova Scotia in 1992.

Typically, lake trout are long and slender, with a deeply forked caudal fin. This distinguishes them from other chars, such as speckled or brook trout.

The overall coloration is light spots on a dark background, that varies from light green to almost black. Lake trout do not have the red spots found on speckled trout. Orange or red-orange may be present on the pelvic, pectoral, and, especially, anal fins, but this feature is usually more apparent in northern populations. A narrow white border is present on the lower fins, but it is never as immaculate or as wide as on the fins of a speckled trout. Dark bands may be noticeable on the sides of spawning males, but are not present in every population. Even during the mating season, the sexes can rarely be distinguished on the basis of color. Young lake trout or par have seven to twelve vertical bars on their sides. These are called par marks. The number of par marks varies, and the spaces between them are usually equal to or slightly greater than the width of an individual bar.

Lake Trout Facts
  • Lake trout may not spawn every year, and northerly stocks tend to have fewer spawning fish in any one year. This is thought to be a function of photoperiod, shorter growing season, less abundant food, and the unproductive nature of many northern lakes.
  • Lake trout are “negatively phototropic”; they avoid light.
  • Lake trout spawn at night.
  • In large bodies of water such as the Great Lakes, lake trout may migrate up to 300 km (186 mi) to their spawning grounds.
  • Lake trout scales are unreliable for aging purposes because the annuli cannot be distinguished. Researchers determine age by reading otoliths, which are calcified tissues of the inner ear used by fish for maintaining equilibrium and balance. The oldest fish on record, taken in the Northwest Territories, was aged at 65 years.
  • Female lake trout are crossed with male speckled trout to produce a fish known as splake, in a process called artificial hybridization. Hatcheries produce splake because this hybrid grows very quickly.

Some Fishing Facts

  • Lake trout are easily caught because of their predatory nature.
  • Lake trout are caught with spinning gear, flies, spoons, jigs, and live bait, which are commonly used on down riggers. It is illegal however to use live bait in Montana’s Flathead Lake.
  • Winter angling for lake trout through holes in the ice is a popular sport in some areas.
Natural History

Namaycush is a North American Indian name that means “dwellers of the deep”. Lake trout inhabit deep, clear, rocky lakes with preferred temperatures of about 10°C (50°F) and oxygen levels of six to twelve milligrams per liter. Lake trout have an upper lethal temperature of about 23.5°C (74.3°F). They also inhabit shallow lakes and rivers, but this is usually in the northern parts of their range. The lake trout is a bottom oriented species regardless of depth. Juveniles are usually found in deeper water than adults. This may be a mechanism for survival, because adults are cannibalistic.

Lake trout also feed on aquatic insects, crustaceans, and smaller fish such as minnows, lake whitefish, yellow perch, alewives (gaspereau), and rainbow smelt. In large lakes with many fish species, lake trout are typically piscivorous, meaning they eat other fish. In smaller lakes, with fewer forage species, lake trout tend to be planktivorous for much of the year. In these lakes, they tend to prey upon small crustaceans and several species of aquatic insects.

Lake trout are fall spawners and normally reproduce every second year from September to November in most parts of their range. Temperature, light, and wind are factors which contribute to the onset and duration of spawning activities. Spawning begins when water temperatures fall to 10°C (50°F) and lower. Lake trout spawn on offshore shoals, near shorelines and points near islands exposed to the prevailing winds. The substrate is a combination of broken rubble and edged rocks 3-15 cm (1-6 in.) in diameter.

Lake trout do not construct reds like most other salmonids, nor do they form single mating pairs. Spawning may involve several females laying their eggs into crevices in the rocks or spaces between the rocks. Several males may fertilize the eggs. The fish do not cover or care for the eggs. Females typically release 800-1800 eggs per kilogram of body weight. Egg incubation lasts for four to five months depending on temperature and oxygen levels. The eggs hatch between February and April, but the fry do not emerge from the rubble until their yolk sacs are absorbed a month later. The fry ascend to the surface to fill their swim bladders and then descend into cooler, deeper water where they remain for two to three years.

Lake trout have few predators with the exception of man and the sea lamprey, which almost wiped out some Great Lakes stocks following the opening of the Welland Canal between Lake Ontario and Lake Erie in 1829. Lake trout eggs are eaten by other fish species, and often by lake trout themselves.