Managing skin fluke infestations without drugs.

I wonder what it is about water depth that can reduce infestation intensity by up to 95%. Is it the distance from the light, cooler water, or what? Interesting article, but brings up more questions than answers.

Aquaculture
Volume 403, Number 1-4 (July 2013)
	Diurnal pattern of skin fluke infection in cultured amberjack, Seriola dumerili, at different water depths
	Authors:	Sho Shirakashi, Chihaya Hirano, Hiroe Ishitani, Katsuya Ishimaru
	Author Affiliations:	no affiliations available
	Source:	Aquaculture, Volume 403, Number 1-4 (July 2013)
	Page Numbers:	19 – 23
	Available Full Text:	Full Text: Subscription Required to view full text Format: PDF Size: Unknown Location: Publisher’s Site Authentication: Publisher’s Site
	Abstract:	Skin fluke infection is a major parasitic problem in the aquaculture industry. Present control measures such as bath treatments are effective for removing flukes from fish but require extensive labour and time. Moreover, bath treatments cause great stress to the fish, and occasionally lead to post-treatment mortality. Our ultimate goal is to develop a culture technique that prevents or lowers the chance of fish encountering larval skin flukes, thus reducing infection. However, little is known about when and where these infections occur on fish farms. We conducted a field experiment at a culture site to determine the diurnal pattern of skin fluke infection at different water depths. Juvenile amberjack, Seriola dumerili, were placed in enclosed mesh cages and exposed to skin flukes at depths of 0, 2 or 4m for 4h during different times of the day. A Neobenedenia girellae infection occurred predominantly at the surface during the mid-day. The infection rate declined considerably during the night. The parasite burden was significantly decreased with water depth, and up to an 80% and 95% reduction in intensities was observed when fish were exposed at a depth of 2 and 4m, respectively. These results suggest that skin fluke infection can be significantly reduced by systematic management strategy and modification of culture techniques.
	Citation:	Sho Shirakashi, Chihaya Hirano, Hiroe Ishitani, Katsuya Ishimaru . Diurnal pattern of skin fluke infection in cultured amberjack, Seriola dumerili, at different water depths. Aquaculture, Volume 403, Numbers 1-4 (July 2013), pp. 19-23, <http://ejournals.ebsco.com/direct.asp?ArticleID=4C74857AD4BA90B1A7D5&gt;
	URL:	http://ejournals.ebsco.com/direct.asp?ArticleID=4C74857AD4BA90B1A7D5