Date: 5 Oct 1998
QUESTION:
Does anyone have any information on methods to control fungus on eggs? I have heard of both formalin and salt treatments via drip application. I am interested in the long term effects of formalin on the eggs and any information on dosage and duration.
Caroline Cherry
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COMMENTS 1:
Formalin drips on eyed trout eggs is standard practice with no
problems. Its use on shortnose sturgeon eggs was postulated to cause the gill plates to be shortened, exposing the gills in some varying degree... but that was never studied in detail to determine if it was indeed true. I doubt it was the cause because varying the timing or amount (concentration) of exposure did not appear to have a cause and effect relationship.
Check with any Federal or State trout hatchery to get their dosages... but watch for the differences in your water chemistry as compared to theirs.
Rick Eager
Swimming RockFish and Shrimp Farm
Meggett, South Carolina 29449, USA
e-mail: dreager@awod.com
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COMMENTS 2:
We are not a commercial sized hatchery, but a University Marine
Laboratory, and in general are not dealing with enormous numbers of eggs. We incubate the small, pelagic eggs in 40 liter static kreisols with aeration adequate to keep the eggs suspended and circulating about the tank. Water is changed daily. The eggs hatch within two weeks depending on temperature. The iodine bath for controlling fungus is ideally done as a general disinfectant bath prior to stocking the eggs into the incubators. It can also be done to combat fungus during the incubation period. Eggs are collected into a sieve (about 250 micron) and the sieve is submerged into a 100 ppm iodine bath for ten minutes. The eggs are then stocked (or restocked) into the sterilized incubators.
Deborah A. Bidwell
Zoology Department
University of New Hampshire, USA
(603) 862-4153
dbidwell@hopper.unh.edu
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COMMENTS 3:
Malachite green or Peroxide will do the job.
James A Mackie
PO Box 14771, Alloa, UK. FK10 2EW
Tel (44) 01259 215136
Fax (44) 01259 211053
www.scoot.co.uk/james_a_mackie/
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COMMENTS 4:
Malachite Green is not an approved drug/chemical for use on food fish in the USA. It has been banned by the FDA for over 10 years now as a carcinogen!
George Nandor
George.F.Nandor@state.or.us
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COMMENTS 5:
The status of malachite green is always a challenging question.
I believe that it is not specifically "banned" in the US, because very
limited FDA / CVM approvals in the US have been given for use of malachite green for control of external fungal infections on adults of endangered salmon species (of course these are not food fish).
I am also under the impression that the concern with malachite green is more with teratogenicity than carcenogenicity.
From a drug regulatory point of view, it is extremely unlikely that
malachite green would ever receive full approval because it is not a pure substance, but a mix of several related dye compounds.
Rob Armstrong
ah355@sonic.net
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COMMENTS 6:
Thank you George for stating the obvious for me - apparently not so obvious to those in the UK. I worked on a Scottish salmon hatchery during 1995 and was amazed by how freely malachite green and formalin was used on eggs and smolt. Sure it worked but at what cost.
Jordan Howarth
mailto:jhowarth@metz.une.edu.au
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