At the AOGAA meeting in January Paul Grindlay gave the following update:
1.1 Invasives/Whirling Disease – Paul Grindlay reported on the Dec 12/19 meeting of the Alberta Whirling Disease Committee. Most of the meeting presented updates on monitoring, lab work, testing, decontamination protocols, public outreach initiatives, signage, aquaculture etc. Most interesting material was from research in the Crowsnest River by Clayton James. His research demonstrated that high levels of infection and mortality require the alignment of three factors:
1. A good population of Tubifex worms
2. Ideal temperature range of 10-15 degrees C
3. Presence of “Young of the Year” fish of less than 10 cm in length
Alignment of these conditions is already causing high juvenile mortality in the lower Crowsnest. The disease is spreading to the upper Crowsnest too.
The Bow River is not experiencing high juvenile mortality. It is suspected that this is because juveniles mostly grow to be larger than 10 cm by the time the water temperature reaches 10 degrees C. If whirling disease is not responsible for declining trout populations in the Bow, then what is? This is the big question. Is it predation, warming, water management, pollution, reduced nutrients, angling pressure or some combination of all of the above?