09-07-2017, 12:53 AM
The average years yield, adult 3 year old male in Ririe has always been under 14" with a few years exceptions. Those exceptions rely on the perfect triad of events rather than the amount of fish planted. The three effects that have to come together to make for a larger 3 year old class is as follows:
1. Heavy snow pack. The kokes feed on plankton and the amount of plankton in the lake depends heavily on the amount of nutrients and minerals carried into the lake via the snow pack.
2. Slow run-off delivery. The longer the the delivery time for the supply of nutrients coming into Ririe, the more food is produced in the biomass.
3. A gentle spring where the temperatures remain low enough for an extended period of time allowing the kokanee to remain up in the top 15' of the water column. Plankton only exists at depths where the light penetration is strong enough for it's growth. Kokanee however, do not like water temperatures above 56.5 degrees. The longer the period of time in the spring that the water remains conducive to plankton generation and the fish being able to feed for extended periods of time at or close to the surface determine the maximum growth rate for the biomass.
The other triple play that comes into context with the size of the fish is having this perfect storm happen three years in a row. Lose one year of growth which is normal and we are back at fish from 12 to 14 inches.
Since Ririe is a narrow and fairly deep gorge, most of the food in the biomass goes unused as the heat is reflected from the sides of the canyon into the water and warms it up faster then the kokes ability to stay near the surface and feed. I believe this is why the F&G biologists saw no harm in planting more fish as a plankton concentration study probably saw no change with the increased numbers of fish planted.
Hope this information helps to understand the complexities of Kokanee growth rates.
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1. Heavy snow pack. The kokes feed on plankton and the amount of plankton in the lake depends heavily on the amount of nutrients and minerals carried into the lake via the snow pack.
2. Slow run-off delivery. The longer the the delivery time for the supply of nutrients coming into Ririe, the more food is produced in the biomass.
3. A gentle spring where the temperatures remain low enough for an extended period of time allowing the kokanee to remain up in the top 15' of the water column. Plankton only exists at depths where the light penetration is strong enough for it's growth. Kokanee however, do not like water temperatures above 56.5 degrees. The longer the period of time in the spring that the water remains conducive to plankton generation and the fish being able to feed for extended periods of time at or close to the surface determine the maximum growth rate for the biomass.
The other triple play that comes into context with the size of the fish is having this perfect storm happen three years in a row. Lose one year of growth which is normal and we are back at fish from 12 to 14 inches.
Since Ririe is a narrow and fairly deep gorge, most of the food in the biomass goes unused as the heat is reflected from the sides of the canyon into the water and warms it up faster then the kokes ability to stay near the surface and feed. I believe this is why the F&G biologists saw no harm in planting more fish as a plankton concentration study probably saw no change with the increased numbers of fish planted.
Hope this information helps to understand the complexities of Kokanee growth rates.
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