Aquaculture (NP106) Annual Report for 2012

Vision: The vision for ARS aquaculture research and technology transfer is to support a 

thriving domestic industry based on improved systems developed through research and 

application of better genetic stocks, improved diets and nutrition, enhanced aquatic animal 

health and consistent water quality. Our program supplies scientific information on

processes, biotechnologies, and management practices to ensure a high quality, safe supply 

of healthful seafood and aquatic products.

Mission: The mission of the Aquaculture National Program is to conduct high quality, 

relevant, fundamental, and applied aquaculture research, to improve the systems for raising

domesticated aquaculture species, and to transfer technology to enhance the productivity and 

efficiency of U.S. producers and the quality of seafood and other aquatic animal products.

The primary aim of the ARS Aquaculture Program, as described in the National Program 106 

Action Plan, is to help develop and ensure an abundant, safe, and affordable supply of 

seafood products within a healthy, competitive, and sustainable aquaculture sector. This

sector is supported by over 4,300 aquaculture farmers that produced in excess of $1 billion 

dollars worth of goods in 2005 (NASS, 2005 Census of Aquaculture). 

Fiscal year 2012 was the third year of externally-reviewed five-year project plans. Although 

these project plans guide most of the efforts of the laboratories, we remain flexible enough to 

respond to additional problems and opportunities. NP106 research is spread across the 

spectrum from fundamental to applied, aiming to solve problems through long term high 

impact research. NP106 published over 100 articles over the past two years in peer-reviewed 

scientific journals.

NP106 People in 2012

We welcomed David Marancik, DVM, Ph.D. into ARS as a post-doc with the National 

Center for Cool and Cold Water Aquaculture in Leetown, West Virginia. In Stoneville,

Mississippi, Craig Tucker, a familiar presence as the Mississippi State University Director of 

National Warmwater Aquaculture Center, moved across the hall to become the Research 

Leader of the Catfish Genetics Research Unit. With the closure of the Chestertown, 

Maryland, Aquatic Animal Health Research Unit, (Auburn, Alabama, North facility) Joyce 

Evans moved to the Catfish Genetics Research Unit in Stoneville, Mississippi. Peter Bechtel 

moved from the Alaskan project on fishery co-products, to the Southern Regional Research 

Center in New Orleans, Louisiana, to lead the new project on adding value and developing 

new products for catfish. Joining Peter on the project is the research chemist John Bland, 

coming to aquaculture from the Formosan Subterranean Termite Research Unit in New 

Orleans. Dunhua Zhang also joined the Aquaculture program from the Formosan 

Subterranean Termite project, moving to the Aquatic Animal Health Research Unit in 

Auburn, Alabama.
Several scientists have retired or left from USDA/ARS. Chhorn Lim retired in January 2013, 

after an extremely productive 25 years in nutrition and fish health with ARS. Mark Camara 

left the Newport, Oregon, Shellfish Genetics worksite (at the Oregon State University 

Hatfield Marine Research Laboratory) for a position in New Zealand.

Barry Hurlburt continues in New Orleans but has moved from the aquaculture project into 

the peanut allergen project.

Awards and Recognitions:

Scientists in the Aquaculture National Program were well recognized nationally and 

internationally over the past year, with many invited presentations. The following scientists 

in the Aquaculture National Program were recognized with prominent awards:

Frederic Barrows, Trout Grains Project, Aberdeen, Idaho:

2012, USDA/ARS Pacific West Area, Scientist of the Year

Frederic Barrows, Trout Grains Project, Aberdeen, Idaho:

2012 Excellence in Aquaculture Award, Illinois Soybean Association

Kevin Schrader, Natural Products Utilization Research Unit, Oxford, Mississippi, and

John Davidson and Steve Summerfelt, Conservation Fund Freshwater Institute, 

Shepherdstown, West Virginia:

2012 Aquacultural Engineering Society Best Paper Award:

Schrader, K.K., Davidson, J., Summerfelt, S.T. (2010). Evaluation of ozonation on levels of 

the off-flavor compounds geosmin and 2-methylisoborneol in water and rainbow trout 

Oncorhynchus mykiss from water recirculation aquaculture systems. Aquacultural 

Engineering. 43, 46-50

Craig Tucker, Catfish Genetics Research Unit, Stoneville, Mississippi:

2012 Aquaculture Achievement Award, Delta Council

National Program 106 involves efforts in 9 units at 111 different locations on 20 projects

performed by nearly 100 scientists (46 ARS scientists and an equal number of collaborating 

scientists). Technology transfer activities included invention disclosures including a large 

number of attenuated bacterial strains, several new and ongoing Cooperative Research and 

Development Agreements (CRADA) and over 20 new and ongoing Material Transfer 

Agreements (MTA). These agreements cover transfer of Atlantic salmon germplasm to 

commercial producers, supply of rainbow trout families to university, industry and State 

hatchery collaborators, development of vaccine and vaccination methodologies and transfer 

of specific pathogens strains for vaccine work. A number of additional activities to transfer 

technologies to other scientists and to industry partners were also completed. Among the

outstanding examples is the ongoing effort to improve hybrid catfish production at 

Stoneville, Mississippi, where scientists are working closely with a number of hatchery 
operators in the Mississippi Delta region having tremendous success increasing the number 

of hybrid fry produced across the industry. Another example is the rapid development of 

numerous fish diets including new ingredients. The Trout Grains project has worked with 

multiple collaborators to improve, develop and test new ingredients, leading to new feed 

formulations and opportunities for ingredient manufacturers.

Across the program, researchers maintained beneficial collaborations with a number of

international investigators and laboratories. Canada and Norway lead the list in terms of the 

active collaborations. Work ranges across cooperation on salmon breeding efforts and 

information sharing on recirculating aquaculture systems with Canadian counterparts to 

exchange with the Norwegian Aquaculture Protein Center on feed processing and with 

NOFIMA (Norwegian Institute of Food, Fisheries and Aquaculture Research) on fish health 

and well-being in recirculating systems. Our aim is to form real partnerships that have 

benefit to the United States and to cooperating countries. These relationships increase the 

depth of our intellectual capital with original ideas from different perspectives. We had a 10 

day tour of facilities in West Virginia and the Southern states, Alabama, Mississippi, and 

Arkansas by potential new cooperators, in fish health and feed development areas, from the 

National Agricultural Research Agency in Brazil, EMBRAPA. In addition ARS scientists 

traveled to Brazil, China, Norway, and other countries to make presentations and develop 

new collaborative opportunities.

Funding: During fiscal year 2012, total funding for Aquaculture research was 

approximately $33.4 million. Balancing the continuous need for additional funding with the 

maintenance of our core mission is a constant challenge and the resulting dialog is a big part 

of the innovative process. These additional funds have come from grants, other government 

agencies, foundations and industry. The National Center for Cool and Cold Water 

Aquaculture (Leetown, West Virginia), Trout-Grains project (Hagerman, Idaho), Catfish 

Genetics Research Unit (Stoneville, Mississippi), Aquatic Animal Health Research Unit 

(Auburn, Alabama), the shellfish habitat utilization lab (Hatfield, Oregon), and the National 

Cold Water Marine Aquaculture Center (Franklin, Maine) and the Freshwater Institute 

(Shepherdstown, West Virginia) all received extramural funds.

Research Results

The following section of the report summarizes the specific high impact research results 

addressing objectives in the current National Program Action Plan.

Genetic and Genomic Resources 

Third generation of selectively bred yellow perch reach market size four months sooner 

High performers of yellow perch strains were identified, tagged, genotyped, and 

selectively bred by ARS researchers at Milwaukee, Wisconsin, and their University of 

Wisconsin at Milwaukee partners. As a result of two generations of selection, the time 

needed to reach market size has been reduced from eleven to seven months. Faster 
growth to market size will enable producers to have multiple production cycles in a single 

year, which increases profitability of commercial yellow perch aquaculture operations. 

Additionally, genetic differences in resistance to viral hemorrhagic septicemia virus have 

been demonstrated and will enable further genetic improvement in disease resistance.

Reducing the use of fish oil in salmonids feeds

Feed is the highest variable cost in aquaculture production, with fish oil being one of the 

most expensive feed ingredients. Fish oil in trout feed is the primary source of the healthy 

omega-3 fatty acids EPA and DHA found in trout fillets. Scientists with the Small Grains 

and Potato Germplasm Research Unit in Aberdeen, Idaho, evaluated the ability of several 

families of rainbow trout to convert plant oils into long chain omega-3 fatty acids and 

store them in their tissues. The study clearly demonstrated that genetic variation exists 

between families for this ability. Rearing rainbow trout improved for this trait should 

maintain the beneficial fatty acids currently found in trout fillets while reducing feed 

costs and the industry's current reliance on fish oil. 

Rainbow trout selected for growth on plant-based feeds have increased tolerance for 

soy’s anti-nutritional factors

Fishmeal is an expensive component of many trout diets. To reduce the reliance on 

fishmeal based feed, scientists with the Small Grains and Potato Germplasm Research 

Unit in Aberdeen, Idaho, have selectively bred a strain of rainbow trout that grows faster 

and more efficiently when fed a fishmeal-free, plant-based diet. The improved fish have 

adapted parts of their intestinal tract to utilize a plant-based diet more efficiently without 

developing the intestinal inflammation observed with conventional strains of rainbow 

trout when fed such diet. Increasing our understanding of how trout adapt to being fed 

plant-based diets will aid in the continued development of improved strains of trout.

Production and evaluation of hybrid catfish using various strains of blue catfish

Hybrid catfish production (female channel catfish crossed with a male blue catfish) has 

expanded greatly in the United States over the past 5 years. While channel catfish strains 

have been well characterized over several decades, little information is available on blue 

catfish germplasm regarding production traits, especially in channel x blue hybrid catfish 

offspring. ARS scientists with the Catfish Genetics Research Unit in Stoneville, 

Mississippi, have obtained blue catfish from several geographic sources (strains) and 

initiated a program to determine the effects of blue catfish strain and individual within 

strain on hybrid offspring growth and fillet yield. Significant effects of individual male

and female parent on offspring performance were identified and importantly, these effects 

were additive. This result means that the effect of parent on offspring performance is 

predictable and improvements will be cumulative. Based on results of these trials, blue 
catfish germplasm that produces superior performing hybrid offspring will be identified 

and released to the industry.

Atlantic salmon selected for increased growth and weight released to industry

Commercial salmon producers in the Eastern United States are legally required to culture 

stocks certified to be of North American origin. Therefore they use stocks that are only a 

few generations removed from wild, unselected stocks with relatively poor performance 

under farming conditions. ARS researchers at the National Cold Water Marine 

Aquaculture Center at Franklin, Maine, are selectively breeding salmon of North 

American origin for faster growth and evaluated the growth of salmon from their 

breeding program in commercial sea cages in collaboration with industry. A salmon line 

selected for increased growth, more than 50% larger than unselected control fish, has 

been generated and germplasm was released for commercial production. Genetic gain 

has been 7-10% per generation. Utilization of improved germplasm will increase the 

profitability and sustainability of coldwater marine aquaculture in the United States while 

providing a quality seafood product to U.S. consumers.

Evaluation of channel x blue and purebred channel catfish performance from 4 

commercial farms

Channel x blue hybrid catfish production and use by the catfish industry have increased 

substantially in the last 3 to 5 years, however channel catfish females that cross well to 

form hybrids and blue catfish breeds with superior farmed performance have not yet been 

identified. ARS scientists with the Catfish Genetics Research Unit in Stoneville, 

Mississippi, are working to determine the effects of channel catfish strain, and female 

within strain, on hybrid offspring growth and carcass yield. This project will provide 

information to determine which strains produce superior hybrid offspring, how much 

differences in offspring performance are due to differences in individual female parent, 

and if purebred channel offspring performance is predictive of hybrid offspring 

performance. This information is key to producers as they develop breeding plans to 

improve hybrid catfish performance.

Genetic mapping of stress response to handling in rainbow trout

Under typical fish farming conditions, fish are routinely exposed to crowding, handling 

and similar stressors. How fish respond to such stressors impacts their growth, feed 

efficiency, immune response, and reproductive development. Through genetic mapping 

approaches ARS researchers at the National Center for Cool and Cold Water Aquaculture 

(NCCCWA) at Leetown, West Virginia, identified 8 chromosomal regions linked to 

stress response in rainbow trout and are measuring genetic variation for this trait within 

and between populations. This research will improve our understanding of the 
physiology of the stress response as well as provide a more rapid and accurate way to 

identify rainbow trout best able to perform well under routine farming stressors.

Animal Performance, Well-being and Efficiency 

 Controlling sexual maturation in farmed fish 

The long periods of time required for most farmed fish to reach sexual maturity 

significantly slows genetic improvement and impedes fingerling production. Kisspeptins 

are newly recognized proteins that naturally control when animals enter puberty. 

Scientists from the Stuttgart National Aquaculture Research Center in Stuttgart, 

Arkansas, showed that sexually immature male white bass entered puberty more quickly 

and that adult female white bass had larger ovaries containing more mature eggs 

following administration of kisspeptins. Together these findings highlight the potential of 

kisspeptin treatment in fish to accelerate and help control reproductive timing. This will 

speed breeding and improve year-round reproductive potential.

Sex steroids linked to muscle degradation in rainbow trout 

Sexual maturity affects growth and meat quality in most terrestrial livestock but little is 

known about their actions in fish. Understanding how sex steroids affect muscle growth 

and quality will enable development of strategies for more efficient fillet production. 

ARS researchers at the National Center of Cool and Cold Water Aquaculture at Leetown, 

West Virginia, discovered increased rates of muscle protein degradation occur in sexually 

maturing rainbow trout with high sex steroid levels, even when feeding rate is high. 

Subsequent studies indicated that estrogens, but not androgens, act directly in muscle to 

reduce protein retention by both increasing rates of protein degradation and decreasing 

rates of protein synthesis. These data demonstrate that harvesting before sexual 

maturation and sex steroid exposure should result in the most efficient production of high 

quality fillets in the rainbow trout.

Development of a non-lethal and rapid method for reliable identification of gender in 

yellow perch

Yellow perch females grow faster than males, so aquaculture producers would like to 

separate yellow perch by gender. Despite this difference in size, it is difficult to 

distinguish the sex of immature animals without causing harm or death to the animal. To 

address this, ARS researchers at Milwaukee, Wisconsin, developed criteria that enable 

gender identification in yellow perch, based upon the coloring and shape of the external 

reproductive openings, with an accuracy exceeding 97%. This non-lethal method 

provides a useful and practical tool that will enable aquaculture producers and researchers 

to sort sexes for 1) development and management of broodstocks (breeding stock) prior 

to, and during, breeding; 2) conducting multi-tank replicate experiments aimed at 
studying gender-specific differences in yellow perch; and 3) identification of the fastest 

growing individuals of each sex in yellow perch broodstock genetic-selection programs 

dedicated to developing improved growth performance in this species. The criteria 

developed for gender identification in yellow perch are easy and inexpensive.

Evaluation of a vertebrate gonadotropin releasing hormone to induce ovulation in 

catfish 

Production of hybrid catfish has expanded substantially in the United States over the past 

5 years; however, availability of hybrid fingerlings still does not meet the demand. ARS 

researchers at the Catfish Genetics Research Unit in Stoneville, Mississippi, are working 

to improve efficiency of hybrid catfish production through better control of ovulation and 

stripping of high quality eggs. A synthetic spawning hormone has been tested and found 

to perform as well as the mammalian hormone analog which is currently used in 

commercial hybrid catfish production. The synthetic hormone also improved 

synchronization of ovulation, improving the number of eggs ovulated by each female, 

and higher numbers of fry were produced compared to the mammalian form of the 

hormone. Increased production efficiency of hybrid fry should lower the cost of hybrid 

fry production in the U.S. catfish industry.

Regulators of feed efficiency in catfish 

Factors that control feed efficiency are not well understood in catfish. Therefore ARS 

scientists in Stoneville, Mississippi, conducted research to investigate the role of 

mitochondrial respiratory chain enzyme activities on low and high Feed Efficient (FE) 

families of catfish. Mitochondrial complex enzyme activities showed that the activities of 

the liver mitochondrial complexes (I, II, III, and IV) were all lower in the low FE family 

compared to the high FE family. Enzyme activities of the muscle and gene expression 

from the liver and muscle are currently being evaluated. Understanding how the 

mitochondrial respiratory chain controls feed efficiency will help researchers develop 

strategies to improve feed efficiency in catfish.

Nutrient Requirements, Nutrient Composition of Feedstuffs, and Expanding 

Alternative Ingredients 

Use of alternative feed ingredients to reduce production costs of catfish

The prices of soybean meal and corn, the two most commonly used traditional feed 

ingredients in channel catfish diets, have increased dramatically in recent years. Using 

less-expensive alternative feed ingredients to partially replace soybean meal and corn 

would reduce feed cost. Scientists at Mississippi State University (MSU) at Stoneville, 

Mississippi, investigated the use of alternative feedstuffs corn gluten meal, distillers dried 

grains with solubles, and cottonseed meal, as replacements for soybean meal and corn in 
diets for pond-raised channel catfish. Up to 50% of the soybean meal in channel catfish 

diets may be replaced by a combination of these ingredients without markedly affecting 

the physical quality of feed pellets, fish growth, processed yield, and body composition. 

The results also show that corn can be reduced to a level of about 15-20% without 

affecting fish performance.

Summer diets for hybrid striped bass 

High daily summertime feeding rates can result in concentrations of ammonia in pond 

water that are toxic to hybrid striped bass. In response, farmers may curtail feeding or 

switch to a lower protein feed, both of which reduce production. With input from 

Mississippi-based hybrid striped bass producer, Nature's Catch, scientists at the Stuttgart 

National Aquaculture Research Center, Stuttgart, Arkansas, demonstrated that a diet with 

higher digestible protein and fat that was supplemented with deficient amino acids, 

maximized growth and nutrient retention and reduced ammonia waste production. Fish 

feed manufacturers are using new digestibility coefficients, recently developed at this lab, 

in their diet formulations for hybrid striped bass, feeding the new summer diet 

formulation, and improving summer production.

Organic ingredients can substitute for fish meal in fish feed

The USDA is currently developing standards for organic aquaculture production. 

Agricultural products for use in fish feeds that will meet these organic standards are 

sought as substitutes for fish meal. A scientist from the Stuttgart National Aquaculture 

Research Center, Stuttgart, Arkansas, in collaboration with scientists from Kentucky 

State University, Frankfurt, Kentucky, showed that tilapia fry fed a diet formulated with 

organic soybean meal and organic yeast, and supplemented with specific amino acids 

grew as well as tilapia fry fed a fishmeal based diet. Identifying organic agricultural 

products that can substitute successfully for fish meal in fish diets that meet the standards 

for an organic label is an essential step towards achieving organic aquaculture 

production.

Developed a method to recover high value co-products from grain-based ethanol 

production 

There is increasing production of fuel ethanol from grains in the United States and the 

primary co-product is corn distiller's dried grains with solubles (DDGS). The quantity of 

this relatively low value product is also increasing and is used primarily in cattle but its 

use for feeds is limited due to an imbalance of nutrients. Scientists with the Small Grains 

and Potato Germplasm Research Unit in Aberdeen, Idaho, developed a new processing 

method that will produce more consistent, higher protein DDG and two new products, a 

protein and a mineral source with improved nutrient profiles. Feeding trials with rainbow 

trout demonstrated that both products are highly digestible, which is vitally important to 
the trout industry. This new process can be easily added to the existing process and it 1) 

reclaims valuable phosphorus and protein from the solubles and 2) separates the nutrients 

into distinct products, thus increasing the overall flexibility, economic value, and 

sustainability of ethanol production.

New protein source for aquafeeds developed from almond processing waste 

Approximately 2 billion pounds of almonds are produced in the United States each year 

and approximately 25% is considered waste in the form of broken pieces and fine 

particles and is fed to cattle. Scientists with the Small Grains and Potato Germplasm 

Research Unit in Aberdeen, Idaho, in collaboration with U.S. based Adaptive BioResources LLC, developed a process to partition this waste into several new products for 

both the human food and aquafeed markets. Trout feeding studies have demonstrated 

high digestibility and palatability for the ~60% protein almond meal. Identifying and 

developing new sources of plant-based protein for aquafeeds will increase the 

profitability and sustainability of aquaculture production and increase the value of coproducts.

Improving Health 

Development of a live attenuated vaccine and in-pond vaccination platform to protect 

catfish against enteric septicemia of catfish

A new vaccine and vaccine delivery platform have been developed resulting in 

exceptional protection against Enteric Septicemia of Catfish (ESC). Based on 

experimental pond studies conducted under conditions similar to the commercial 

production setting, vaccination increased survival, fish size, and feed consumption while 

improving the feed conversion ratio by approximately 40.4%. The improved feed 

conversion could represent a 30% reduction in feed costs, while improved production 

efficiencies in vaccinated fish increased gross sales over 100%. Similar results were 

obtained over two years of field testing. Field and laboratory research is being conducted 

as part of the USDA licensing process for live attenuated vaccines.

Parasite vector for a bacterial pathogen in channel catfish

There is limited information on whether parasites act as vectors to transmit pathogenic 

bacteria in fish. Scientists at the Aquatic Animal Health Research Laboratory at Auburn, 

Alabama, conducted studies with Ichthyophthirius multifiliis (Ich, parasite) and 

Edwardsiella (E.) ictaluri (bacterium) to determine the interactions between the parasite, 

the bacteria, and the catfish. This study provided evidence that the parasite, Ich, can carry 

E. ictaluri into channel catfish. The parasite, when exposed to E. ictaluri bacteria could 

pass the bacteria to channel catfish. The transmission ability of parasites is particularly 

important at fish farms because the introduction of parasites either from wild fish or from 
other farms could unintentionally involve the introduction and/or transmission of 

bacterial diseases.

Vaccines developed to protect tilapia against Streptococcosis

Streptococcosis is a hyperacute systematic disease that affects both cultured and wild fish 

species in various aquatic environments (freshwater, estuarine, and marine). ARS 

researchers at Auburn, Alabama, developed attenuated vaccines to protect tilapia against 

both Streptococcosis agalactiae and Streptococcus (S.) iniae. The attenuated S. iniae

vaccine offered tilapia 100% protection for over 2 months post vaccination. In addition, 

the attenuated S. iniae vaccine offered 78% to 100% protection against multiple isolates 

of S. iniae. The use of these vaccines will protect tilapia against streptococcosis, and 

decrease the economic losses caused by strep induced mortality affecting the aquaculture 

industry.

Identification of the causative agent of a significant disease outbreak in farmed 

rainbow trout and development of an autogenous vaccine

Emerging pathogens are a significant threat to U.S. Aquaculture. An ARS researcher at 

Leetown, West Virginia, isolated a new gram positive bacterial pathogen causing 

significant loss of rainbow trout in North Carolina. The pathogen was found to be similar 

to Weissella sp. Associated with recent disease outbreaks in farmed rainbow trout in both 

China and Brazil; this is the first report of this pathogen in the United States. At the 

request of stakeholders, the National Center of Cool and Cold Water Aquaculture

developed and validated an effective autogenous vaccine which is now in commercial 

production and in use at North Carolina farms affected by this pathogen. Early pathogen 

detection and the rapid development and implementation of a vaccine are aiding control 

efforts and reduce the likelihood of further pathogen dissemination in the United States.

Release of disease resistant germplasm to the rainbow trout industry stakeholders

Bacterial cold water disease, caused by Flavobacterium psychrophilum, is a widelydistributed and economically-important disease that results in elevated mortality and 

deformity rates in rainbow trout aquaculture. Currently there are only limited 

chemotherapeutics, and no commercial vaccines, available for control or prevention of 

the disease. ARS researchers at the National Center for Cool and Cold Water Aquaculture 

at Leetown, West Virginia, have developed the ARS-Fp-R rainbow trout line through 

multiple generations of genetic selection for improved disease resistance, and have 

demonstrated the line has superior resistance to the bacterium in laboratory challenges 

and field trial evaluations. The release of 80,000 embryos from 52 pedigreed families to 

Clear Springs Foods Inc. (Buhl, Idaho) and Troutlodge Inc. (Sumner, WA), and 

approximately 50,000 embryos from 43 families to the Utah Division of Wildlife 

Resources, will allow industry and government stakeholders to propagate or introgress 

the line and produce future generations of fish with improved disease resistance.
Bacterial binding sites influence susceptibility to columnaris disease

Columnaris is a major fish bacterial disease causing significant losses to the aquaculture 

industry. New research suggests that bacterial binding sites in the gills were stimulated 

in response to columnaris exposure. ARS scientists in Stuttgart, Arkansas, demonstrated 

dramatic evidence of differential immunity to columnaris after exposing fish to the 

bacteria and examining the quantity of binding sites in the gills of two different families 

of channel catfish. They determined that one family was susceptible to the disease, while 

the other was completely resistant. The quantity of binding sites in the gill was strongly 

increased in the columnaris-susceptible family, but the catfish protected from columnaris 

disease had reduced binding sites present in the gills. The nutritional status of the fish 

also had an effect, with a far greater amount of binding sites in the gill of unfed fish 

relative to well-fed fish. These findings will be applied to develop screening techniques 

for enhancing resistance to columnaris.

Pharmacokinetics of florfenicol in channel catfish

Researchers from Mississippi State University, College of Veterinary Medicine (MSUCVM) at Stoneville, Mississippi, conducted pharmacokinetic studies of florfenicol in 

catfish. These studies along with laboratory and field efficacy studies were pivotal in 

obtaining Food and Drug Administration (FDA) approval for the use of florfenicol 

medicated feed to treat Flavobacterium (F.) columnare and Edwardsiella ictaluri

infection in catfish. In addition, these studies along with one conducted by the United 

States Fish and Wildlife Service in Bozeman, Montana, cleared the way for approval of 

florfenicol to treat F. columnaris infection in all freshwater-reared warmwater fish. The 

drug is prescribed under a veterinary feed directive and has been shown extremely 

effective in controlling bacterial infections in warmwater fish.

The development of molecular test for the detection of significant catfish pathogens in 

environmental and tissue samples

Disease is one of the leading causes of fish loss and poor yields in catfish production. 

Researchers from Mississippi State University (Mississippi Agricultural and Forestry 

Experiment Station, MAFES and College of Veterinary Medicine, CVM) have developed 

and validated assays for the detection and quantification of a number of significant agents 

causing serious disease in channel catfish. The assays provide reliable methods for the 

detection and quantification of pathogens in pond environments and are being used for 

rapid diagnostic evaluations and evaluation of treatment efficacies associated with 

recommended disease management strategies and research. Using this technology, risk 

assessment models for proliferative gill disease (PGD) have been developed and are 

being used by diagnostic services to mitigate losses during catfish pond stocking and 

restocking programs. Additionally, a bacterial assay for the causitive agent of motile 

aeromonas septicemia is currently in use in our and other laboratories to confirm the 

presence/absence of the emerging virulent strain of Aeromonas hydrophila in suspect 
cases. In addition to their diagnostic benefits, these assays provide a means to conduct 

epidemiological and environmental studies and evaluate how management strategies alter 

pathogen loading rates in commercial catfish ponds. This information will be used to 

optimize disease management practices aimed at maximizing production efficiencies and 

economic returns.

Identification of a new species of trematode affecting production efficiencies of catfish 

Recently, ponds of catfish with reduced growth and feed intake were examined for 

disease. Snails were collected and found to be releasing a trematode parasite, previously 

thought inconsequential to catfish health. Challenges with actively shedding snails 

demonstrated this trematode can infect channel catfish, and cause mortality. Molecular 

analysis identified this parasite as Drepanocephalus (D.) spathans, a digenetic trematode 

known to parasitize the double-crested cormorant. Based on the high numbers of D. 

spathans infected snails collected from commercial catfish ponds, this trematode species 

is likely a significant pathogen of channel catfish and has been included in disease 

monitoring efforts.

Production Systems and Products

Lower water exchange rates save money without negative impacts on health and 

performance of Atlantic salmon

Water availability and cost of water use are two key variables for fish production in 

recirculating aquaculture systems, so one research goal is to minimize the rates of water 

exchange while maintaining excellent conditions for fish. Atlantic salmon were reared by 

ARS researchers at Leetown, West Virginia, for 6 months in replicated water 

recirculating systems operated with either high water exchange (97.5% of system flow 

recirculated, i.e. 2.5% new water added each day) or low water exchange (99.75% of 

system flow recirculated, 0.25% new water added each day). Fish performance, health 

and welfare were measured. By study’s end, no significant differences were determined 

in growth, survival, and other fish health outcomes even though the low water flushing 

treatment operated with 10-times less water use. Though significant differences in a 

variety of water quality parameters were noted, none of these parameters was outside 

acceptable ranges for raising salmonids. This study illustrates that Atlantic salmon 

perform well in recirculating systems with low water exchange and demonstrate that 

farmers with limited water resources can compete in salmon production.

New cascade column and low-head pump combination reduces the energy requirement 

for producing fish in water reuse systems

Construction and operation costs of recirculating aquaculture systems is a major 

impediment to adoption of these recirculating aquaculture system technologies. 

Scientists at the Conservation Fund Freshwater Institute, working with ARS researchers 
at Leetown, West Virginia, developed a sidewall box containing a forced-ventilated 

cascade column and low-head axial flow pump to provide a new high water flow and low 

lift method of gas exchange just outside of the culture tank. Water and air flow rates were 

measured, plus energy consumption, dissolved oxygen and carbon dioxide transfer rates 

and efficiencies. The novel application was found to reduce electric and oxygen costs by 

as much as 50% compared to more conventional partial water reuse technology. The 

sidewall box cascade column and low-head pump can be integrated into the design of 

much larger recirculating aquaculture systems to improve gas control, provide culture 

tank rotation, and reduce total power requirements and the carbon footprint of these 

systems.

Biofloc technology systems reduce the intensity of common off-flavors in channel 

catfish

Pre-harvest off-flavors described as "earthy-musty" in catfish that are produced in earthen 

ponds continue to present problems for this industry. A novel, highly intensive, static 

water production system, called the biofloc technology production system, produces high 

yields of channel catfish. ARS researchers at the Natural Products Utilization Research 

Unit, Oxford, Mississippi, and the Stuttgart National Aquaculture Research Center, 

Stuttgart, Arkansas, with a scientist at the University of Arkansas-Pine Bluff, Arkansas, 

demonstrated that the biofloc technology production system also inhibited the growth of 

common blue-green algae responsible for producing off-flavor compounds, and that the 

intensity of off-flavor problems were reduced in catfish grown in these systems. This 

discovery provides catfish producers with an alternative to using earthen ponds to grow 

catfish and provide an on-flavor, high-quality product to consumers.

Development of an improved aerator for the catfish industry

Paddlewheel aerators have been used for aeration in aquaculture for over 30 years. They 

transfer a lot of oxygen to the water but also move a large volume of water which spreads 

the aeration effort over the entire pond volume. Thus, a great deal of equipment and a 

large amount of power is required to prevent low dissolved oxygen (DO) conditions in 

commercial ponds. ARS researchers at Stoneville, Mississippi, have developed a new 

aerator, the Power Tube Airlift (PTA) which can concentrate DO into a small zone of 

water in a pond using less energy than traditional methods. At a 20-ft sparger water depth 

preliminary testing indicates that the PTA has an oxygen transfer rate aeration efficiency 

approximately equal to a 10-hp paddle-wheel aerator. Fewer moving parts and improved 

efficiency would reduce the costs associated with repair and maintenance, and lower 

power (electricity) consumption, respectively. Two commercial-scale PTAs have been 

installed in an 8-acre catfish production pond for onsite field testing, and field trials on 

commercial farms are expected to begin in FY 2013. This invention has a patent 

application currently pending with the U.S. Patent and Trademark Office.
Development and validation of split pond production systems to increase production 

efficiency of catfish

Most United States aquaculture production comes from large earthen ponds. 

Disadvantages of traditional pond production are the need for continuous management of 

pond oxygen concentrations, sporadic algae-related fish off-flavors, losses to avian 

predators, difficulties in disease control, inefficient fish harvesting, and lack of tight 

control of water quality. Scientists from Mississippi State University (MSU) at 

Stoneville, Mississippi, have addressed these constraints by modifying ponds to 

physically separate the fish-holding function from the life-support and waste-treatments 

functions. A commercial scale system, called the “split pond” has been developed and 

validated at Stoneville, Mississippi. The split pond is constructed by dividing an existing 

earthen pond into two unequal sections with an earthen levee and then linking the two 

sections with water flow. Validation studies indicate that the split-pond is easy to manage 

and that fish production can be tripled compared to traditional ponds. Based on research 

in this project, split ponds have been widely adopted by the catfish farming industry. 

More than 1,000 acres of commercial ponds have been built with at least an additional 

1,000 acres under construction or planned construction.

Intensive production of hybrid catfish

ARS researchers at Stoneville, Mississippi, have completed three years of research on the 

intensive production of channel catfish female X blue catfish male hybrids (hybrid 

catfish) using 0.25-acre ponds at the National Warmwater Aquaculture Center in 

Stoneville and 1-acre ponds under contract at the Delta Western Research Center in 

Indianola, Mississippi. Speeding time to harvest and improving efficiency of feed 

conversion to flesh are critical for improving profitability of catfish production. Research 

has demonstrated that hybrid catfish can tolerate a slightly lower dissolved oxygen (DO) 

concentration in the morning than channel catfish. They also have a greater tolerance to 

common diseases affecting catfish, resulting in a greater feed intake through spring and 

fall when diseases are more common. Due to an overall greater feed intake, fish grow 

faster and reach harvest size sooner. It appears that with an adequate DO concentration (a 

minimum of 2.5 mg/L in the morning) fish density has little effect on growth rates at least 

up to stocking rates of 11,000 fish per acre. Continued adoption of hybrid catfish by the 

industry is expected to result in increased profits (reduced production costs) due to faster 

growth (reduced production cycle), increased survival, and improved feed conversion 

ratios.