Recreational Advisory Issued at Crowley Lake Due to a Harmful Algal Bloom
SACRAMENTO – The Lahontan Regional Water Quality Control Board (Water Boards)
are urging fisherman and recreational users to stay out of the water at Crowley Lake
located in Mono County. Localized areas of the lake were tested to confirm that the lake is being impacted by Harmful Algal Blooms (HABs). The lake is posted with a
recreational advisory of “DANGER” to alert lake users of the elevated risk. Recreators
are encouraged to follow the below guidance until further notice.
• Stay out of the water until further notice, including watercraft.
• Do not let pets and other animals drink or go into the water, or go near the scum.
• Stay away from scum, and cloudy or discolored water.
• Do not eat fish or shellfish from this water.
• Do not use this water for drinking or cooking. Boiling or filtering will not make the
A volunteer citizen monitoring partner noticed visual observations of a potential bloom
while sampling during the Labor Day Pre–Holiday Assessment at Crowley Lake. Sample results confirmed toxins present at danger level thresholds in a sample collected from
the marina area. Caution level toxins were present at a second sample collected near
the Hilton Creek drainage.
Note that cyanobacteria, a group of organisms that form harmful algal blooms, can produce potent toxins. Health risks are associated with HABs as they produce
dermatoxins that can cause skin inflammation, which can cause itching skin and rashes, as well as gastrointestinal distress, headaches, agitation and weakness, or abnormal
breathing if HAB material is swallowed while swimming. Dogs and children are most
susceptible to exposure because of their smaller body size, increased potential to
swallow water while swimming, and tendency to stay in the water longer. If you suspect exposure, wash your children and dog immediately. Due to the size and toxicity of the
bloom with increasing temperatures and decreased precipitation this time of year, the
bloom may proliferate and alter its potential to produce toxins.
The bloom occurring in the lake appears suspended on the water’s surface. Bloom
conditions can change rapidly, as the winds and waves move or concentrate the bloom
into different regions of the lake. In some areas, the bloom may concentrate and form a film or scum on the water surface. The color of the water may also appear discolored as bright or dark green and brown.
The Water Boards will provide regular updates to inform the community when postings are removed on the California HAB Reports Web Map.
The Water Boards recommend that people practice healthy water habits
while enjoying the outdoors this summer at your local lake, river or stream:
• Heed all instructions on posted advisories if present
• Avoid algae and scum in the water and on the shore
• Keep an eye on children and pets
• If you think a harmful algal bloom or toxic algal mats are present, do not let pets and
other animals go into or drink the water or eat scum/algal mats on the shore
• Don’t drink the water or use it for cooking
• Wash yourself, your family and your pets with clean water after water play
• If you catch fish, throw away guts and clean fillets with tap water or bottled water
• Avoid eating shellfish if you think a harmful algal bloom is present
Get medical treatment immediately if you think that you, your pet, or livestock has
gotten sick after going in the water. Be sure to alert the medical professional to the
possible contact with cyanobacteria. Also, make sure to contact the local county public
To report a bloom, do one of the following:
• Fill out the Bloom Report form on the HABs Portal:
• Email: [email protected]
• Call the HABs hotline: 1–844–729–6466 (toll free)
• Contact your County Public Health Office
For more information about HABs, please visit:
California Harmful Algal Blooms Portal
California Department of Public Health Resource Page
(From Mono County and the California Water Boards)