Lake Virginia Management District
7/8/26: It has been noted that there are an above average number of dead fish on the lake recently. We have one compressor not currently functioning. Below is the response from WI Lake & Pond Resource as to whether or not the compressor would have potentially caused it and what they feel is the culprit:
No, one compressor alone will not make the world of difference although the more aeration the better when dealing with the consequences of planktonic algae species the lake is prone to. Over the years, I have observed a few dead fish on the lake but not a larger/outbreak of dead fish as you mentioned. There have been multiple times where blowers would go down historically for long periods of time without seeing a large fish kill event. The benefit of the multiple aeration system stations is that a really good chunk of the system is still operating unlike in the past.
Planktonic and/or blue-green algae species create harmful algae blooms on your lake. These can certainly impact oxygen and pH during vast day/night swings as well as producing toxins that can cause direct harm to fish. Without treating large blooms or nutrient controls from upstream sources, there is a lot of fuel for algae blooms and there has been here for a very long time. At night, this harmful algae respirates which can produce toxins that kill fish directly and/or you can experience even a minor localized fish loss event due to toxin production or local oxygen loss. Even a 20x20 area in a more slack water area with heavy algae accumulation can cause fish loss over night as some fish may refuse to leave those areas. Combine this with the wettest April in WI history followed by the driest and warmest May in WI history, conditions now may be a bit unprecedented for algaeaccumulation and stress on fish.
Joey Berg
Eldorado Branch Manager
Update7/9/26 from the WI DNR:
I emailed fisheries staff last night when we got back from our survey and they documented and confirmed the fish kill. They were in the field this morning through the early afternoon, I chatted with Casey/Nate just before noon, and Casey will be writing up the documentation for the event when they get back to the office. The dissolved oxygen was low even later in the day after they were out there a couple hours. I would expect it to be lowest at dawn (algae respiring) and a large spike later in the day as the algae photosynthesizes (diurnal cycling) but they were seeing low numbers well after dawn. Casey was also wondering if the large numbers of aerators were potentially cycling anoxic water. A large volume of curlyleaf dying off can high biological oxygen demand on the lake. The bacteria that are consuming the dead plants could be creating a high biological oxygen demand and also releasing nutrients that may have exacerbated the algal activity. We had a stretch of mid-90s and algal activity has significantly increased exacerbating the issue. The aerators may also be expediting the issue by quickly cycling the anoxic water near the bottom throughout the lake.
Did you/the lake by chance get hammered with the big storm cells that pushed through over the weekend? We had a couple incidents last year where after a large rainfall, the wetlands were releasing anoxic water to the lakes (larger systems with large wetland areas) and that is a possibility as well. I think the more normal, slow warm up we had this spring benefitted curlyleaf (anecdotally I’ve seen it increase on many lakes in the southern part of the state). These are my initial thoughts unless there is another variable that we are not accounting for.
I am not sure what the fish kill disposal methods are but maybe Casey and Nate have answered this question in the past and would be able to provide some guidance. I would error on the side of caution if collecting and disposing of the fish because Casey observed some blue-green algae congregated at the north end of the lake (likely similar to where the fish are congregating with the south winds today). The normal precautions should be taken for human health reasons (below).
“Casey reports it is indeed thousands of fish. All species, all sizes. There are some live fish remaining but O2 levels are very low. O2 is closest to zero in the areas where the aerators are operating. Casey wonders if the aerators are actually making it worse by circulating anoxic water.
Highest DO right now is up in the shallows in the weeds, DO around 1.7 in those areas and fish are surviving there. Once you get outside the weed line, the DO drops under 1ppm quickly.
Is it possible the aerators are making this worse?
Casey notes a moderate algal bloom. Worse algae on north end, SW wind may be pushing water up into that end. Greenish blue tint to the water in parts of the north end. South end of the lake is pretty clear water.
That’s the update for now.
Nate”
Here’s some information about staying safe around blue-green algae blooms:
The Wisconsin Department of Health Services has fact sheets on Staying Safe and Healthy in Wisconsin's Lakes, Blue-green Algae and Dog Safety, and Safe Fishing Practices & Fish Consumption. These fact sheets show you the blue-green algae conditions to watch out for and to avoid. If you have very young children or dogs who will be swimming in the water, it’s safer to keep them out when floating areas of blue-green algae are present, and definitely stay out when conditions resemble those in the fact sheet photos.
Local public health departments have the jurisdiction for beach monitoring in Wisconsin, but most departments do not have the capacity for blue-green algae monitoring. Monitoring can be very challenging as blue-green algae concentrations can change very rapidly, so the best thing you can do is to learn what blue-green algae look like and assess water conditions for yourself before swimming:
Blue-green algae are in all water bodies in Wisconsin. Waters with high nutrient levels are more susceptible, but even lakes with excellent water quality may experience surface blooms, especially after periods of calm weather when wind can blow blue-green algae into 1 area of a lake.
Blue-green algae can also grow on lake bottoms and rivers as mats, which sometimes float to the surface.
It’s always a good idea to avoid swimming in areas with a lot of tiny particles in the water, opaque “pea soup” water, or dark-colored floating mats. All of these may be blue-green algae. Always avoid swallowing untreated surface water because it may contain bacteria, viruses, and parasites that could make you sick.
If small children and dogs are swimming, choose the clearest water possible for them to swim in.
Don’t let dogs swim or play in shallow, stagnant areas where blue-green algae mats may be growing on the bottom and dislodged by disturbance.
Don’t let dogs eat floating material in the water, or material washed up on shore.
In dogs, water intoxication (from swallowing too much water) and heat stroke share symptoms with blue-green algae poisoning. Give dogs plenty of breaks from playing and retrieving in lakes and give them flat objects for retrieval instead of balls. Always provide shade and fresh, clean water to drink, and wash them off with clean water after they swim, so they don’t lick blue-green algae from their coats.
There’s more information at DNR's Blue-green Algae Page and DHS's Blue-green Algae Page. You can also view a 2021 Wisconsin Water Week DNR presentation on blue-green algae on YouTube.
I know it is a big bummer when this happens, but it is not out of the normal on shallow nutrient rich lakes. We have a couple every year unfortunately, especially on this hot summer days.
Regards,
Arthur J. Watkinson
Work Phone: 608-220-6245
arthur.watkinson@wisconsin.gov
Spillway repairs are now planned for fall 2026 (previously fall 2025) due to construction bids coming in significantly higher than expected. We expect that putting out a spring bidding request will draw more favorable bids. The fall timeline is per a request by the DNR to minimize the impact on the fish in the lake. Stoplogs will need to be removed and replaced. The logs will start to be removed beginning on or after September 1st, with them all beeing out by September 15th per DNR requirements. The lake level is expected to drop by approximately an additional 30-40 inches when this occurs in order to seal the spillway and replace the stoplogs.
Next Meeting
Date: 09/12/2026
Time: 9:00 AM
Location: Excelsior Town Hall, 100 E. Broadway, Rock Springs, WI
Many thanks to Patriot Shore Services for the pier at the boat landing, providing this to us at no cost.
Please see the News & Notices & Resident Resources pages for current events and information.