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United States Department of Agriculture

Agricultural Research Service

Related Topics

Research Project: Management of off-Flavors and Undesirable Bacteria in Aquaculture

Location: Natural Products Utilization Research

2013 Annual Report


1a.Objectives (from AD-416):
1)Discover and develop management strategies for mitigating pre-harvest microbial-derived off-flavors in fish cultured in re-circulating aquaculture systems (RAS) to help reduce off-flavor delayed harvest. 2)Discover and conduct primary development of novel natural and natural-based compounds for controlling disease causing microorganisms in pond-based production systems.


1b.Approach (from AD-416):
Isolate and identify the microorganisms responsible for the most common environmental off-flavors in finfish cultured in recirculating aquaculture systems (RAS). Perform laboratory physiology studies on the off-flavor microorganisms to determine the environmental and nutritional conditions that favor growth and production of the off-flavor compounds. Conduct depuration studies to identify factors such as adipose content of the fish flesh and fish size that may affect depuration rates. Perform efficacy studies to determine if activated carbon filtration can be utilized to reduce levels of the off-flavor compounds in the RAS water and subsequently in fish flesh. Determine the efficacy of antifouling coatings to reduce biofilm formation on RAS culture tank walls and subsequently reduce levels of microbial off-flavor compounds in RAS-cultured fish. Conduct bacterial bioassays to identify natural or natural-product based compounds as potential leads for use in managing diseases in catfish aquaculture. Perform primary development of promising natural compounds identified from bacterial bioassays for use as therapeutic drugs to manage common catfish diseases and improve catfish health.


3.Progress Report:
In collaboration with The Conservation Fund’s Freshwater Institute, Shepherdstown, West Virginia, the effects of hydrogen peroxide pretreatment of depuration systems to remove biofilm and removal of aeration media were found to aid in purging earthy and musty off-flavors in rainbow trout after being held in these systems for 6 to 10 days. Recommendations to producers are to utilize disinfection of purging systems with hydrogen peroxide and remove aeration media to aid in depuration of common off-flavors from fish flesh. A patented natural-based algicidal compound incorporated into a slow-release-based coating and found to inhibit algal growth on polyvinyl chloride (PVC) is undergoing further research and development by LIG LifeSciences, Export, PA, through a Phase II Small Business Innovative Research (SBIR) grant awarded in 2013. Research continued for a third year on the evaluation of biofloc technology (BFT) systems for reducing the intensities of earthy and musty off-flavor problems in cultured channel catfish. These BFT systems were found to be unfavorable for the growth of the common types of blue-green algae responsible for producing earthy and musty compounds that can occur in catfish production ponds. Physiology studies on the effects of temperature on the production of biomass and earthy/musty off-flavor compounds by bacteria isolated from recirculating aquaculture systems identified the specific bacterial species contributing to the presence of earthy and musty off-flavors in the cultured fish flesh. In collaboration with the University of Mississippi and Mississippi State University, a novel natural compound isolated from sycamore tree leaves was discovered to possess antibacterial activity against one type of bacteria responsible for causing a common disease in pond-raised channel catfish. In addition, studies using channel catfish determined that feed containing the natural compound from sycamore leaves was palatable to the fish and did not appear to be toxic (e.g., no difference in weight gain compared to fish receiving feed without the natural compound).


Review Publications
Schrader, K., Harries, M.D., Darwish, A.M. 2013. In vitro comparisons of the inhibitory activity of florfenicol copper sulfate and potassium permanganate towards Aeromonas hydrophila and Flavobacterium columnare. Aquaculture Research. 44:212-219.

Brown, T.M., Cerruto-Noya, C.A., Schrader, K., Kleinholz, C.W., Mireles Dewitt, C.A. 2012. Evaluation of a modified Ph-shift process to reduce 2-methylisoborneol and geosmin in spiked catfish and produce a consumer acceptable fried catfish nugget-like product. Journal of Food Science. 77(10):377-383.

Nakoano, H., Schrader, K., Mamonov, L.K., Kustova, T.S., Mursaliyeva, V.K., Cantrell, C.L. 2012. Isolation and identification of flavobacterium columnare and Steptococcus iniae antibacterial compounds from the terrestrial plant Atraphaxis laetevirens. Journal of Agricultural and Food Chemistry. 60:10415-10419.

Schrader, K., Avolio, F., Andolfi, A., Cimmino, A., Evidente, A. 2013. Ungeremine and its hemisynthetic analogues as bactericides against Flavobacterium columnare. Journal of Agricultural and Food Chemistry. 61:1179-1183.

Last Modified: 10/22/2014
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