09-11-2017, 09:06 PM
Great question!
As others have mentioned, kokanee size at adulthood mostly depends on two major things:
1. Lake productivity (how much food/plankton the lake can make). Of course, this can change from year-to-year depending on runoff, drought, etc. Biologists don't have much control over this part.
2. Numbers of kokanee (more kokanee = smaller size). This depends on stocking AND natural reproduction from any spawners (also hard to control... think Deadwood weir that controls spawning numbers).
Kokanee all eat the same thing: plankton. So, when there are more kokanee, there is less food to go around, and they reach adulthood at smaller sizes. Yes, there is some differences in age/genetics etc., but that usually isn't the driving factor of ultimate size.
Stocking kokanee is a tricky business! The idea is to get the best combination of size and catch rates. Lakes like with huge kokanee usually don't have very many of them, so while you might catch some big ones, you probably won't catch very many.
Stocking at Ririe got a big increase in 2013, then back a little in 2014 to around 300K a year fairly consistent. The intention is to dial in the right stocking numbers to get that good combination of average size with good catch rates.
IDFG is still evaluating the Ririe kokanee fishery to see how the stocking numbers are working. If you have more questions, Dan Garren in the Idaho Falls office would be happy to talk about it. He'll have the details on how the lake is managed.
[signature]
As others have mentioned, kokanee size at adulthood mostly depends on two major things:
1. Lake productivity (how much food/plankton the lake can make). Of course, this can change from year-to-year depending on runoff, drought, etc. Biologists don't have much control over this part.
2. Numbers of kokanee (more kokanee = smaller size). This depends on stocking AND natural reproduction from any spawners (also hard to control... think Deadwood weir that controls spawning numbers).
Kokanee all eat the same thing: plankton. So, when there are more kokanee, there is less food to go around, and they reach adulthood at smaller sizes. Yes, there is some differences in age/genetics etc., but that usually isn't the driving factor of ultimate size.
Stocking kokanee is a tricky business! The idea is to get the best combination of size and catch rates. Lakes like with huge kokanee usually don't have very many of them, so while you might catch some big ones, you probably won't catch very many.
Stocking at Ririe got a big increase in 2013, then back a little in 2014 to around 300K a year fairly consistent. The intention is to dial in the right stocking numbers to get that good combination of average size with good catch rates.
IDFG is still evaluating the Ririe kokanee fishery to see how the stocking numbers are working. If you have more questions, Dan Garren in the Idaho Falls office would be happy to talk about it. He'll have the details on how the lake is managed.
[signature]