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Publication #Cir107

A Beginners Guide to Water Management—Fish Kills1


In an effort to alleviate concerns voiced by the general public, the Florida LAKEWATCH (FLW) program recently published a 16-page booklet that discusses five of the most common natural causes of fish kills including: low dissolved oxygen; spawning fatalities; mortality due to cold temperatures; diseases and parasites; and toxic algae blooms. Human-induced fish kills are also covered along with a section on fish stress—a component of virtually every fish kill situation. The last section of the circular provides steps one can take to determine the cause of a fish kill. This includes a listing of fish health diagnostic laboratories for those who want to take a more active role and are willing to collect fish and/or water samples for analysis.

Keywords: Alafia River, algae bloom, Aphanizomenon, aquatic microbes, biological activity, Cylindrospermopsis, Anabaena, contaminants, dead fish, decomposing plants and/or algae, diseases, dissolved oxygen (DO), ecosystem, fish kill, fish stress, general adaptation syndrome, hormones, hormone induced, human impacts, human induced, lake turnover, live fish, Microcystis, mortality, naturally occurring fish kills, oxygen levels, parasites, Prymnesiam, osmoregulation, oxygen depletion, rainfall, spawning fatality, stratification, tilapia, toxic algae, water sample, water temperature

Note: Circular 107 is available in Portable Document Format (pdf) only. It can be obtained as a single PDF file by clicking on the "Printer Friendly Version" link above (file size = 2.2 MB).

Photos used with permission as credited.



This document, CIR107, is the seventh of a series of information circulars dedicated to familiarizing citizens with the language and techniques used by those involved in water management. © June 2003 1st Edition. Reviewed by Mark Hoyer January 2017. Printed copies are available through the UF/IFAS Extension EDIS website ( and also from the Florida LAKEWATCH website ( Readability grade level: 12.0


Florida LAKEWATCH (FLW) is a research and public outreach program coordinated within the UF/IFAS Department of Fisheries and Aquatic Sciences. FLW facilitates public involvement in the management of Florida waters by training citizen volunteers to collect monthly water samples, algae samples, and water clarity data from a lake or waterbody of their choice. Over time, this information is used to document nutrient levels and/or to predict biological productivity. For more information about the program or to obtain FLW data, call 1-800-LAKEWATch (1-800-525-3928) or view the website at

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.