Last July, after a large but not uncommonly large rainfall, the fish and other aquatic creatures were killed in a 6.5 mile stretch of the South Branch of the Whitewater River. Three state agencies–Agriculture, Natural Resources and Pollution Control –could not figure out why the fish died.
The 367 page “South Branch Whitewater River Unified Fish Kill Response” details the investigation and findings.
Priaxor was initially identified as a possible cause of the fish kill: “The MDA investigations found that the fungicide product ‘Priaxor’ was applied in the agricultural fields around the river stream where the fish kill incident occurred, and was considered the most probable pesticide to potentially affect aquatic system at the time of the fish kill in the SBWWR.” (page 37 of the fish kill report)
The chemical data sheet (priaxor-fungicide-label-3fluxaproxad-pyroclostrobinbasf.pdf ) for Priaxor says “(t)his pesticide is toxic to fish and aquatic invertebrates.” In the Surface Water Advisory section of the data sheet it says “(t)his product is classified as having high potential for reaching aquatic sediment via runoff for several months or more after application….(r)unoff of this product will be reduced by avoiding applications when rainfall is forecast to occur within 48 hours.” Department of Agriculture investigators asked aerial sprayers about applications in the eight days before the fish kill so they had no information about any earlier spraying that either singly or cumulatively could have caused the fish kill. Department of Agriculture investigators did not ask whether there had been spraying 48 hours before the kill.
Nonetheless the report says “(a)pplication records were collected, reviewed, and determined to have been applied according to the requirements on their labels….In addition, most (emphasis added) applications were found to have occurred to fields a long distance from the SBWWR and/or had a large buffer area between the field and the SBWWR, or applications occurred outside of the fish kill period. As a result, pesticide applications were not suspected to have caused or contributed to the fish kill.” (page 53)
The findings on page 85 offer a different take: “Although fungicides were being applied to area agricultural fields, prior to the fish kill, no evidence of illegal pesticide applications were found.”
Another of the findings was “(t)his fish kill was likely the result of a short duration, acutely toxic event. With this type of event, fish die rapidly and there is often little or no accumulation of toxic compounds in fish organs and tissue.” (page 85) Yet the fish were analyzed as if accumulated toxins had killed them. “Trout gill tissue was removed, cleared with formaldehyde….tissue samples…were ground and combined into a single composite sample for metal and fungicide laboratory analysis.” (page 40) The sediment in the gills offered the best evidence of the toxin that killed the fish. It was thrown away.
Folks are asking if the Whitewater report was deliberately misleading. Reading the report, it is hard to say whether the Agriculture Department was simply incompetent or if it deliberately made choices to avoid finding that a fungicide caused the fish kill. Either way, the outcome is the same. The agencies have escaped the responsibility to do anything to prevent the next fish kill.
Jeff Broberg, geologist and trout fisherman, analyzed the report in a Star Tribune commentary piece and concluded that current agricultural practices killed the fish.
Dave Orrick of the Pioneer Press has a good report with the right conclusion: the fish kill should not have happened.