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Water Quality Update for July 2, 2021

While this year’s HABs program was scheduled to “officially” begin in early August, the intense temperatures we have been experiencing over the last few weeks gave us a hunch that we should start earlier. With our training sessions held in June, volunteers were ready to rise to the occasion!

On June 29th, we had our first official visual bloom report of the season from one of our returning volunteers. An area of visible surface streaking was observed approximately 3 miles down on the east side of the lake, in 2-3 feet of water about 10-15 feet off shore. By the time a HABs team leader was able to visit the site to get a sample, the bloom had dissipated.

On July 1st, we received a report around 10:00 am of a potential bloom area by a trained sampling volunteer on the west side of the lake, and 2 samples were collected from 2 different shoreline areas expressing different levels of cyanobacteria. These samples were transported to the Finger Lakes Institute in Geneva for analysis on a fluoroprobe, an instrument used by FLI laboratory staff to measure levels of blue green chlorophyll and species of cyanobacteria. Official results are forthcoming but samples are above the DEC bloom threshold of 25 ug/L.

These recent observations, combined with a slight decrease in the weekly average water clarity reported by our secchi disk volunteers, is telling us that we may begin to experience isolated areas of blooms in the coming weeks, especially on hot, calm, dry days. Please understand, we are nowhere near lake-wide bloom conditions, as these early reports have been isolated in nature. Watershed staff did site visits at multiple locations and no other blooms were observed at that time. As we know, conditions can change rapidly, and there is potential for increased cyanobacteria concentrations when the conditions are right. Please use your visual indicators to look for signs of active blooms. As recommended by the DEC, if you see it, avoid it.

Volunteers and watershed staff will be continuing daily observations throughout July, August and September and we will communicate any significant changes in bloom activity through our weekly email updates, on our website, and on our facebook page. Stay tuned!

Update on the Recent Fish Die Off CLWA and the Canandaigua Lake Watershed Council fielded several calls in early to mid June regarding increased numbers of dead fish found along shorelines. While we typically might see some die off in late spring brought on by factors such as post-spawning stress, rapidly increasing water temperatures, and ecological changes in the food web, this spring’s die off was more sustained. DEC Region 8 Fisheries staff was contacted to investigate and samples were collected and brought to Cornell Veterinary School for analysis.

DEC Region 8 Fisheries provided the following update:

DEC Fish Die off Update

DEC investigated recent reports of a fish die-off affecting rock bass, sunfish, smallmouth bass, and white sucker in Canandaigua Lake. Samples were obtained from impacted white sucker and smallmouth bass for analysis at the Cornell Veterinary School.

Results came back showing an infection of the bacteria Aeromonas. Aeromonas is commonly found in water and by themselves, are not a concern. DEC suspects that the warmwater fish in Canandaigua Lake became stressed from spawning, temperature swings, or some other stressor. This resulted in their immunity being lowered and allowed the bacteria to infect the fish. Aeromonas does not pose a threat to humans or pets utilizing Canandaigua Lake.

As always, people should not drink unfiltered lake water and obviously sick fish should be avoided. If stressed or dead fish are handled, people should wear gloves or wash their hands with soap and water after. With proper preparation, healthy fish are safe to eat. People should continue to report large numbers of dead fish to DEC at 585-226-5343 or


More Information on Blue Green Algae

Click below for our Harmful Algae Bloom brochure.

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