Kokanee Spawning Wraps Up at Lake Mary Ronan
By angelamontana

Posted: November 5, 2019

Somers, MT — Montana Fish, Wildlife & Parks hatchery staff from Flathead Lake Salmon Hatchery recently completed the annual gathering of kokanee eggs that will benefit lakes across the state.

Lake Mary Ronan, a popular kokanee fishing destination in northwest Montana, serves as the egg source for Montana’s hatchery-produced kokanee. The eggs will hatch in December and eventually be distributed as 2-to3-inch kokanee in the spring of 2020 into 28 Montana lakes.

Originally stocked in Montana over 100 years ago, kokanee are a popular fish species known for their flavor, catchability and sporting qualities. Kokanee are effectively a freshwater version of the Sockeye Salmon native to many Pacific Northwest lakes. Although larger kokanee will eat small fish, their typical diet consists of zooplankton and any available insects like midges. Some individuals may reach larger size but an average “keeper” kokanee ranges from 10 to 12-inches in Lake Mary Ronan.

“We typically stock only those waters with absent or very limited wild kokanee spawning,” FWP Region 1 Fisheries Manager Mike Hensler said. “Some lakes we stock have some natural reproduction but known predators or other factors like poor quality spawning habitat that limit that population. An example is the Thompson Lakes west of Kalispell. By stocking Lower Thompson Lake, we can augment the wild kokanee population in all the lakes enough to improve catch rates.”

FWP staff at the Flathead Lake Salmon Hatchery use a device called a Merwin trap to capture mature kokanee seeking spawning possibilities in Lake Mary Ronan. The trap consists of a net stretching 150 foot in length from shore to a floating spawning platform that cover a net pen fish cannot escape. The crew uses the barge as a floating fish spawning factory.

Two to four people will handle up to 100,000 fish during the spawn. Eggs and sperm are first collected separately then ultimately brought together in small batches for fertilization. The fertilized eggs are then placed in insulated containers and hauled to the hatchery for incubation. The incubation period is typically 60-65 days until hatching.

Upon hatching, the kokanee will continue development as a “sac-fry” on the bottom of the hatchery raceway. The sac-fry will use a reserve of energy from their yolk sac for further muscle, organ and skeletal development. The fish hatch before they have the ability to eat. The yolk sac is absorbed in about 3 weeks and finally have the complete digestive tract and the urge to seek out food.

Located in Somers and built in 1912, the Flathead Lake Salmon Hatchery also produces westslope cutthroat trout, Arctic grayling, and brook trout as space allows following spring salmon stocking.

FWP operates 12 fish hatcheries across the state, and these hatcheries annually stock approximately 45 million fish for sport fishing opportunities and native trout restoration across more than 830 lakes or reservoirs and over 20 rivers or streams.