Moss Discoll with the Klamath Water Users Association analyzes the data from various sources monitoring salmonid health. Recently he summarized...
For fish sampled between 4/20 and 4/26, although roughly half of juvenile Chinook in the Scott-Shasta reach exhibited exposure to C. shasta, essentially none at measurable levels in terms of infection (i.e., qPCR C. shasta DNA “copy number over 3 logs”). The prior survey (4/12) found one in every six fish having been exposed, but again at negligible levels.
With respect to actual fish catch data, out of 364 juvenile Chinook salmon sampled at four sites between 4/26 and 4/29, nine (9) fish exhibited some sort of “distended belly” (i.e., 2%). That was eight (8) fish at the Bogus Creek frame net and one (1) fish at the I5 rotary screw traps and frame nets. Only two such fish had been found previously (one each at I5 and Kinsman between 4/12 to 4/15).
One fish at Bogus Creek out of 217 sampled at all four sites had “pale or worse” gill color. One such fish had been found previously (at I5 in the 4/12-4/15 sample)
Water temperatures have increased, most notably into the mid-50s (F) at the Kinsman site (just upstream Scott River), which would be expected to result in an increase in C. shasta infection rates. Again, spore content and temperature are correlated with disease rates, with 20 spores per liter and/or 20 degrees Celsius (68 degrees Fahrenheit) being the apparent inflection point.
One apparent observation is the lack of any discernable effect of the “surface flushing flow”, although to be fair, annelid and polychaete data should be where the effect is most apparent. KWUA is working on obtaining that data.
This year – from the initial justification for the flush to its subsequent results – would seem to reinforce the conclusion that under the current conditions (i.e., Hardy flows out of the four hydroelectric reservoirs) salmonid disease is essentially unavoidable but for: 1) favorable water temperatures, and/or 2) manipulated (“surface flushing”) flow events. This year would further seem to add weight to the fact that water temperatures are the real key to keeping disease in check – fish have been and continue to exposed notwithstanding the partial flush, yet have a low to negligible level of infection.
Read the Arcata Fish and Wildlife Office 25 April 2022 Update.
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