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Many of you have responded to me about a DO drop as to the cause of the fish kill. Would these fish not move to waters with better DO levels? Are the so keen on guarding the nest that this is not an option? At 500 acres, the whole lake did not suffer from poor DO. Also, some of you have mentioned ingestion of the pellets. It was not Copper Sulfate. It was a herbicide to treat big leaf pondweed. Does anyone have any literature or stories of fish digesting herbicide pellets?
Thanks again for all the talk on this topic. The lake association appreciates it!
Jon
-----Original Message-----
From: Scientific forum on fish and fisheries on behalf of Timothy Smith
Sent: Fri 1/27/2006 6:22 PM
To: [log in to unmask]
Cc:
Subject: Re: Spring fish kill
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Jon,
The mention of CuSO4 may or may not be appropriate. It is strictly an
algaecide and isn't used to control vascular plants. Some lake managers
will apply it in granular form (if they are too lazy to dissolve it first).
If copper sulfate or any chemical were ingested in pellets directly by fish
that might concentrate the dosage enough to cause a kill (I have heard of
this happening but have never seen it).
Certainly the most common form of fish kill after chemical application is
due to low DO. The species you mentioned would have been onshore and most
directly affected by low DO. Is it possible that more fish died than you
actually witnessed? Larger fish (such as mature individuals guarding nests)
are more vulnerable to DO kill than smaller fish. Were large fish the only
ones that died?
If that's true, then I would think more in terms of a DO event. If all
sizes of fish of one or two species died, perhaps the pellet ingestion
scenario is more likely.
>From: "Eynon, Jon S" <[log in to unmask]>
>Reply-To: Scientific forum on fish and fisheries <[log in to unmask]>
>To: [log in to unmask]
>Subject: Spring fish kill
>Date: Fri, 27 Jan 2006 13:55:10 -0500
>
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>Just before Labor Day of 2005 a 500 acre lake in Indiana had a fairly
>substantial fish kill. The fish killed were mainly bluegill and redear,
>most likely on the nest at this time. No other types of fish were found
>dead. The kill occurred shortly after a company was brought in for
>aquatic weed control and "shot pellets" of herbicide from a boat towards
>the shoreline. I am not sure of the type of herbicide.
>
>Can someone give me a quick explanation as to why this would kill only
>the bluegill and how they might have died? Could it have been from
>direct exposure to the chemical or from the DO drop that could have
>occurred? Would they not leave the nest and head for better conditions?
>I am sure that there are many variables in play here, but I am looking
>for someone with just general thoughts on this strange occurrence. We
>have had weed control in the past but never a fish kill like this.
>
>Thanks in advance for any help!
>Jon
>
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