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16 FRED P. MEYER AND ROGER L. HERMAN <br />The mechanism of death in natural kills may be <br />easily determined but the underlying cause may not <br />be immediately obvious. The investigation of non- <br />pollution kills should not stop with the identification <br />of an infectious agent or a determination of oxygen <br />depletion. For example, low flow from a storage dam <br />can be the cause of increased water temperatures <br />in the stream below the dam and thus be the primary <br />cause of a fish kill. Identifying such situations may <br />lead to the modification of water flow management <br />plans to prevent future losses. <br />Documentation must always be precise and con- <br />sistent. Sample sites must be clearly identified so <br />they can be revisited to obtain additional samples, <br />verify any physical conditions, or conduct toxicity <br />tests. All samples must be clearly marked so there <br />can be no confusion as to their identity or as to when, <br />where, how, and by whom they were collected. The <br />chain of custody for all data and samples starts with <br />the on-site investigator and must be continuous <br />through any testing or other examinations that may <br />be conducted, until the case is resolved. <br />Your agency may require an estimate of the num- <br />ber of fish lost, regardless of the cause of death, but <br />if there is reason to believe compensation may be <br />sought or there is a possibility of litigation, a valid <br />estimate of the magnitude of the kill must be made. <br />A guide recommended for this purpose is Special <br />Publication No. 13 of the American Fisheries <br />Society (1982). <br /> <br />Some fish kills affect only one or two species of fish; in this incident, only sunfishes were killed.