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3. Hatch and rear fingerling trout inside hatch houses with secure water supplies <br />known to be free of the WD pathogen. This is absolutely imperative for fish destined <br />for stocking in WD- environments. To every extent possible, this should also be done <br />for fiy/fingerlings known to be vulnerable to the parasite. Current knowledge dictates <br />that these fish should not be moved into nurse basins or raceways on WD+ surface <br />waters until they are at least 3-4 inches in size and more resistant to the parasite. <br />Although this practice may prevent the fingerlings from exhibiting clinical signs, they <br />are still potential carriers of the pathogen. If fish production must be reduced to <br />accomplish this objective, it should be regarded as an acceptable tradeoff, at least in the <br />short term. <br />4. Use state-of-the-art technology to detect/monitor the pathogen. The polymerase <br />chain reaction (PCR) DNA "fingerprinting" of the WD pathogen has been completed <br />and will soon be available commercially for testing and detection of the parasite in fish, <br />worms, and water. Recent research tests at the University of California at Davis have <br />shown that DNA from a single waterborne spore can be detected by the PCR test. This <br />technology has far more utility than current standard testing procedures as it may be <br />capable of detecting the pathogen in all its phases and forms with reliable accuracy and <br />precision. When this technology is commercially available, the DOW should seriously <br />consider acquisition of this testing capability. <br />5. Implement technological solutions: filters, UV light, and ozone. Whether installed <br />independently or in combination, the chosen strategy(s) must be able to stop the <br />infective stage ofM. cerebralis. Various filtration materials (sand and membrane <br />filters), of oxidizing agents (ozone), and ultraviolet light have shown promise against <br />water-borne pathogens. These are not without drawbacks, however. UV light works <br />best in clean water and obviously, to be effective, must be functional 100% of the time <br />(i.e., is susceptible to power failures). Sand filters must be cleaned occasionally, and <br />drum filters can leak or become damaged and may be restricted by water flow rates. <br />Overall, the effectiveness of this solution can be improved with a combination of <br />strategies. For example, in our Bellvue SFH, we are evaluating the effectiveness of <br />using a small drum to pre-filter the water for UV light treatment before it enters the <br />raceway system. Presently, most of this technology cannot be justified economically <br />for rearing units with only surface water supplies. <br />NOTE: The DOW should proceed with caution in adopting any "quick fix" technology. We <br />should avoid acquisition of any expensive control techniques if these methods are not tested <br />and proven effective. Desires to achieve a "quick fix" for WD could leave the DOW <br />burdened with an inventory of expensive capital investments that turn out to be ineffective <br />solutions. For example, ultraviolet light systems cost $200,000 to $250,000 per unit, <br />according to the July 1995 Deloitte and Touche Hatchery System Analysis Report. <br />Installation of these units at all WD+ fish culture facilities would cost $2 million to $3 <br />million. Before going any further with this technology, the unit that has been purchased and <br />44