Chapter 12: Fish Kill Investigation Procedures
Keith B. Floyd
Fish kills are common and pervasive phenomena in all aquatic habitats including marine environments (Figure 12.1); most fisheries managers will encounter fish kills during their careers. The U.S. Environmental Protection Agency (EPA) categorizes fish kills according to the source of the toxicant responsible for it. These categories are municipal operations (sewage systems, power plants, refuse disposal, water supply systems, and public swimming pools), agricultural operations (fertilizer and pesticide application and manure–silage drainage), industrial operations (chemicals, petroleum, mining, food products, paper products, and metals), transportation, “other” operations, and unknown sources. Leading sources of fish kills are agricultural activities, industrial discharges, municipal sewage treatment plant discharges, spills, runoff, and pesticide applications (USEPA 1994). Of 1,454 fish kill incidents reported in 1994, 50% were attributed to pollution (sewage, pesticides, manure, oil and gas, chlorine, and ammonia), 17% to unknown causes, 18% to natural causes (dewatering, drought, high or low temperatures, oxygen depletion, algal blooms, parasites, and diseases), and 15% to ambiguous causes (USEPA 1994). The large percentage of unknown and ambiguous causes is testimony to the difficulty facing a fish kill investigator.
Beginning in the late 1960s, the Southern and North-Central divisions of the American Fisheries Society (AFS) recognized the need to standardize fish kill investigation techniques and to apply monetary values to fish lost during water pollution incidents. They prepared publications on monetary values of fish, which together with fish kill counting guidelines prepared by the AFS Southern Division Pollution Committee, have stood the test of legal courts as a basis for assessing damages by polluters. This chapter is a basic overview and introduction to those procedures as described in the most recent AFS fish kill publication (Southwick and Loftus 2003), which should be consulted for more detailed information. The U.S. Fish and Wildlife Service’s Field Manual for the Investigation of Fish Kills (Meyer and Barclay 1990) provides excellent guidance on determining the specific cause of a fish kill.