Dworshak Reservoir Fishing Report
by Sean Wilson, IDFG fisheries research biologist
It seems like we recently woke up in a different world due to the COVID-19 pandemic. However, Idahoans realize the importance of outdoor activities, like fishing, as part of a healthy lifestyle. If you plan to get out and enjoy some warm spring weather in pursuit of your favorite fish, please do so responsibly. Maintain plenty of distance from others, don’t congregate at access areas, and show each other plenty of patience at boat ramps and on the water. Together we can get through this and continue to enjoy the pastime we love. If you plan to fish Dworshak Reservoir this year, here’s what to expect.
Kokanee
I like to say that kokanee numbers bounce up and down like a Yo-Yo. The good news is that their numbers came up fast last year after bottoming out two years ago. Fishing always seems to be best on the rebound, as kokanee grow better when there are fewer fish to compete for food with. Last summer Dworshak Reservoir had about half a million kokanee in the 10-12 inch range, which is both larger and more abundant than normal. Based on last year’s trawl and hydroacoustic surveys, we anticipate a similar abundance of the larger two year old (age-2) kokanee this year.
Right now the age-2 kokanee range between 8 and 10 inches, and average about 9 inches. This is similar to the size the age-2 kokanee were at this time last year. However, how fast these fish grow this spring and summer will be influenced by how many younger kokanee are out there, as both age-1 and age-2 fish both like to feed on the same thing – Daphnia. Our surveys indicate we could have about twice as many age-1 kokanee this year as we saw last year (assuming average winter survival). This means there will be more mouths to feed and growth rates should drop in comparison to last year. With slower growth rates this spring and summer, we anticipate kokanee size will average around 10 inches this summer, with some up to 11 inches. This is a little smaller than what we saw last year, but this should provide a kokanee fishery that many people will enjoy.
Smallmouth Bass
Dworshak Reservoir is known for big Smallmouth Bass. However, we are learning that Smallmouth Bass growth is fueled by kokanee. So go the kokanee, so go the big bass, just with a little lag. Kokanee numbers bottomed out two years ago, and with this drop in the food supply, bass growth declined resulting in fewer big bass in the reservoir. However, that trend should change as kokanee numbers are bouncing back. If fry survival is good this winter, we should end up with above average numbers of age-1 kokanee allowing bass to grow exceeding well this year. Before bass anglers rejoice, the abundance of age-1 kokanee is yet to be seen and the benefit of increased kokanee abundance on bass growth would be yet another year away. Still, there are some big bass out there to catch, as well as lots of smaller bass, and bass fishing should only improve over the next few years as the kokanee abundance rebounds.
