National Program 106 Aquaculture Annual Report for 2013

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

domestic industry based on improved genetic stocks and scientific information on 

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

(NP 106) Action Plan, is to develop and ensure an abundant, safe, and affordable supply of 

seafood products for the over 330 million U.S. consumers produced in a healthy, 

competitive, and sustainable aquaculture sector, a sector supported by more than 4,300 

aquaculture farmers producing in excess of $1.3 billion worth of goods annually.

Fiscal year 2013 was the fourth 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. NP 106 research is spread 

across the spectrum from fundamental to applied, aiming to solve problems through long 

term high impact research. NP 106 published well over 100 articles over the past two years

in peer-reviewed scientific journals.

Over the summer and early fall, ARS and the National Institute of Food and Agriculture 

(NIFA) together held a number of aquaculture stakeholder meetings. Most were conducted 

by webinar, a new format for us, and one facilitated workshop on catfish held in person in 

Stoneville, Mississippi, with participation from across the catfish growing regions. Inputs 

from these workshops and from the many written comments were considered and 

incorporated into the ARS aquaculture action plan and will inform NIFA leadership, too.

NP 106 People in 2013

In April 2013, Carl Webster, Ph.D. was hired as the new Research Leader/Center Director at 

the Harry K. Dupree Stuttgart National Aquaculture Research Center. Carl came to us from 

Kentucky State University and will continue research on aquaculture nutrition. He has 

already stimulated great teamwork at the center and initiated a series of written outreach 

materials, including a quarterly newsletter and an article in World Aquaculture magazine 

(December 2013).

In May 2013, we welcomed Dina Proestou, Ph.D. into ARS as a new scientist and part of the 

National Cold Water Marine Aquaculture Center. Dina’s research is focused on oysters and 

the genetics of disease resistance; she is located in Rhode Island at University of Rhode 
Island (URI). Dina completed her Ph.D. and a post-doc at URI. Dina came to ARS from the 

Environmental Protection Agency in Kingston, Rhode Island. 

Several scientists have retired from USDA/ARS. Phil Klesius retired in January 2014, after 

an extremely productive 42 years of Federal service with ARS. Phil served as Research 

Leader of the Aquatic Animal Health Research Unit and Location Coordinator in Auburn, 

Alabama, for 26 years. Among Phil’s many accomplishments, he published over 177 

refereed papers, produced 16 patents and developed the only commercially available live 

attenuated fish vaccines in the United States. Gary Banowetz who was the Research Leader

for the West Coast oyster efforts also retired at the end of 2013. Though Gary’s research was 

focused on forage and grasses as a plant physiologist, he worked in fish health early in his 

research career.

Awards and Recognitions:

Scientists in the Aquaculture National Program were well recognized nationally and 

internationally over the past year, with many invited presentations. Dr. Ben LaFrentz from 

the Aquatic Animal Health Research Unit in Auburn, Alabama, was recognized by the 

publisher Wiley and the editors of the Journal of Fish Diseases as one of the journal’s top 

peer-reviewers. A headquarters post-doctoral research associate program award went to Ken 

Overturf (Hagerman, Idaho) for Enhancing aquaculture sustainability by improving plant oil 

utilization and Peter Bechtel (New Orleans, Louisiana) for Postharvest processing to add 

value to catfish.

Over the past couple of years there has been a clear upward trend in the external funds 

awarded to ARS aquaculture scientists, through competitive grants, Foundation supported 

research, Cooperative Research and Development agreements (CRADAs) and the newer 

mechanism of Material Transfer and Research agreements (MTRAs). In new awards just this 

year there have been funds of over $550,000 coming into ARS aquaculture research, with 

Aquatic Animal Health Research Unit, The Trout-Grains project out of Aberdeen, Idaho, and 

the National Cold Water Marine Aquaculture Center attracting the most agreements and 

funding. Our close research partner, The Freshwater Institute, in Shepherdstown, West 

Virginia, also initiated a number of new research agreements.

National Program 106 involves efforts in 11 different locations on 23 projects performed by 

nearly 100 scientists (46 ARS scientists and an equal number of collaborating scientists). 

Technology transfer activities include a number of invention disclosures, 4 new patent 

applications, and 9 new Material Transfer Agreements (MTAs). 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. Collaborative 

research and development based on the bacterial coldwater disease resistant strain of rainbow 
trout from the National Center for Cool and Cold Water Aquaculture has expanded with 

several labs and producers. 

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. 

Funding: During fiscal year 2013, total funding for Aquaculture research was 

approximately $30 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.

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 

Increasing production of healthy omega-3 fatty acids in rainbow trout

The increase in price is making fish oil too expensive to include at desired levels in 

aquaculture feeds. Scientists at the Small Grains and Potato Germplasm Research Unit in 

Aberdeen, Idaho, have determined that genetic variation exists between families for the 

ability to produce and deposit fish oils in flesh. During the last year they have measured the 

variation among families and validated methods for measuring fatty acid levels in live fish. 

This methodology provides the ability to improve fish oil content in filets through breeding, 

and ultimately produce a fish with greater health benefits to humans.

High survival of bacterial cold water disease resistant rainbow trout line in farm trials

Bacterial cold water disease (BCWD) is a frequent cause of farmed trout loss. ARS 

researchers at Leetown, West Virginia, have developed a BCWD resistant rainbow trout line, 

through multiple generations of genetic selection for improved disease resistance. Three 

consecutive years of performance testing of these fish were carried out under farm 

conditions. In five completed trials to date, in which non-select fish were diagnosed with 

BCWD, survival of the select line has been 95% from initial feeding through the early 

rearing phase. This was significantly greater than non-selected fish grown together. In 

addition to greater survival, the select line had a smaller percentage of fish that tested 

positive for the pathogen that causes BCWD. These findings support the release of 

germplasm to stakeholders and the continued evaluation of the select genetic line in largescale production trials.
Genetic improvement for bacterial cold water disease (BCWD) resistance in diploid fish 

also benefits triploid fish production

Fish can be susceptible to many diseases such as bacterial coldwater disease (BCWD). 

Triploid fish, or fish with 3 sets of chromosomes, are sterile, or unable to reproduce. 

Therefore, triploids are often grown in situations where reproduction must be avoided, such 

as release into natural systems. Also, triploids grow to a larger size, and have better fillet 

quality than normal diploids (with 2 sets of chromosomes) during the normal reproductive 

periods, when fillet quality is typically poorer; however, they can be more susceptible to the 

BCWD disease. ARS researchers at Leetown, West Virginia, have previously shown familybased genetic selection can be used to rapidly improve resistance of trout to BCWD, 

increasing survival rate in laboratory challenges from 30% initially, up to 80% in just two 

generations. However, this selection was based on normal diploid fish. Now the researchers 

have demonstrated that selection for improved disease resistance in diploid fish can translate 

into improved disease resistance as triploids. Therefore, the improved line of BCWDresistant trout they developed is of value to producers of both diploid and triploid rainbow 

trout used for both food production and recreational stocking purposes.

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

Commercial culture of channel catfish x blue catfish hybrids continues to increase, but little 

is known concerning the genetic contributions from the blue catfish. ARS scientists with the 

Warmwater Aquaculture Research Unit in Stoneville, Mississippi, conducted two studies in 

which blue male catfish were mated to female channel catfish to determine how to best 

improve growth and carcass yield of hybrid catfish offspring through selective breeding. In 

the first study, blue male catfish from a single strain were mated to multiple channel catfish 

females and hybrid offspring were measured for growth and carcass yield. Progeny were 

reared in communal ponds and parentage was determined by inheritance of DNA markers. 

In the second experiment a similar experimental design was used, but 10 males from each of 

5 blue catfish strains were used in matings. Results of both studies demonstrated a 

significant effect of the female parent on growth and carcass yield, and substantial and 

predictable effects of blue catfish males on growth and carcass yield of hybrid offspring.

This information is critical to efficient selection of purebred blue and channel catfish parents 

to improve performance of hybrid offspring.

 

Animal Performance, Well-being and Efficiency 

Yellow perch females are more valuable than males

Females yellow perch are larger fish and the smaller fish are males that typically fail to 

thrive. Gender identification is extremely difficult until fish mature, which can take up to 

two years. This makes it difficult to separate fish for efficient production, managing brood 

stock for reproduction and it inhibits genetic improvement efforts. Scientists at our ARS 

Dairy Forage and Aquaculture Research Unit in Milwaukee, Wis., along with colleagues 

have developed criteria, based on the shape and color of the external reproductive openings, 

to identify the gender of yellow perch during early growth stages. The gender identification 

algorithm provides a systematic way to reliably identify males from females, ranging from 

about three inches and above in total length. The process is quick, easy and involves a check 

list of questions: the size of the fish, the shape of specific parts and other criteria to 
distinguish males from females. The method is more than 97% accurate and provides a useful 

and practical tool to cost-effectively sort males from females so it can be used to develop and 

manage yellow perch brood stocks, conduct experiments targeting gender-specific 

differences, and to identify the fastest growing females and males for genetic programs to 

improve growth performance.

Chronic nitrate exposure impacts health and well-being of farmed rainbow trout

Maintaining the health and well-being of cultured fish is an important part of cost effective 

and high quality production. The effects of nitrate nitrogen (a byproduct of the breakdown of 

the highly toxic ammonia and nitrite nitrogen) on fish health have, until recently, been 

considered minor. Through ARS-funded research at The Freshwater Institute's Conservation 

Fund in Shepherdstown, West Virginia, juvenile rainbow trout were grown in systems, half 

that were maintained with elevated nitrate nitrogen concentrations and the other half at lower 

concentrations. Over the three-month study period, rainbow trout growth was not negatively 

impacted by the high nitrate treatment; however, survival was lower. Rainbow trout 

swimming behavior was also significantly different between treatments, with more erratic 

swimming in the high nitrate treatments. This study provided strong evidence that high 

normal nitrate levels (e.g. 80-100 mg/L) can have chronic health and well-being impacts on 

juvenile rainbow trout. For the U.S. rainbow trout industry, these results provide valuable 

water quality guidance to limit the impacts of nitrate nitrogen on farmed fish populations.

Effects of male to female ratio and broodfish density on spawning success in pondspawned channel catfish

Channel catfish are reproduced by placing mature male and female catfish in spawning 

ponds, the fish mate in spawning containers placed in the ponds and farmers collect egg 

masses periodically. Improving efficiency of pond spawning would improve profitability of 

catfish farming. ARS scientists with the Warmwater Aquaculture Research Unit in 

Stoneville, Mississippi, conducted two studies to determine if spawning success could be 

improved by altering the ratio of male and female broodstock in the spawning pond. A 

stocking ratio of 1 male to 1 female brood channel catfish (currently the industry standard) 

was compared to a ratio of 1 male to 4 females. Both treatments had a stocking density of 

1,000 pounds (lbs) per acre. The 1:4 stocking ratio produced fewer spawns and fewer fry per 

acre than the 1:1 ratio so farmers would not benefit from decreasing the male to female ratio 

to 1 to 4. In another study, broodstock were stocked at a male to female ratio of 1:2 at 

stocking densities of 1,000 lbs per acre (current industry practice) and 2,000 lbs per acre. 

Broodfish stocked at 2,000 lbs per acre produced approximately twice as many spawns and 

fry per acre. Therefore farmers could benefit by stocking broodfish ponds at higher stocking 

densities than commonly used.

Nutrient Requirements, Nutrient Composition of Feedstuffs, and Expanding Alternative 

Ingredients 

Fish meal-free diets developed for Coho salmon and Yellowtail 

Fish meal has been the primary protein ingredient in fish feeds for decades but increasing 

demand and static supply is driving the search for alternative ingredients to support 

expansion of aquaculture production. Scientists with the Small Grains and Potato 
Germplasm Research Unit in Aberdeen, Idaho, applied research and technology developed 

with rainbow trout to two popular marine species, Coho salmon and yellowtail (amberjack). 

Feeding studies with each species demonstrated that as long as all essential nutrients are 

supplied in a balanced diet, fish meal is not needed for optimal growth and health of the fish.

Reducing or eliminating the dependence of aquaculture feeds on expensive marine harvested 

ingredients will increase profitability and sustainability of aquaculture.

Salmon growth in freshwater and seawater on fishmeal and marine-free diets 

Atlantic salmon producers require knowledge about optimum salinity and feed formulations 

to lower production costs. Salmon were cultured by ARS researchers at Franklin, Maine, in 

either freshwater or seawater on a standard fish meal or marine-free diet. Water source had 

no effect on growth, but fillet color was higher for fish grown in seawater and salmon fed the 

marine-free diet had lower omega-3 fatty acids compared to the fish fed the fishmeal diet. 

Atlantic salmon can be successfully cultured in a wide range of salinities, but proper diet 

formulation is needed to insure product quality.

Use of alternative feed ingredients to reduce production costs of catfish 

The prices of soybean meal, the most commonly used traditional protein source in channel 

catfish diets, have increased dramatically in recent years. Using less-expensive alternative 

feedstuffs to partially replace soybean meal would reduce feed cost. Scientists at Mississippi 

State University at Stoneville, Mississippi, investigated the use of hydrolyzed feather meal as 

a partial replacement for soybean meal in diets for pond-raised channel catfish. Results 

demonstrate that hydrolyzed feather meal may replace about 20% soybean meal in catfish 

feeds without marked impact on fish growth performance when prices are favorable. 

However, caution should be taken when using hydrolyzed feather meal because it reduces 

carcass and fillet yield.

Proper combination or ratio of linoleic and linolenic acid to improve growth and health 

of all male hybrid tilapia 

Published information indicates that tilapia have a dietary requirement for linoleic (LA, n-6) 

series fatty acids (FAs). The optimum levels of n-6 FAs reported were 0.5% and 1% for 

redbelly and Nile tilapia, respectively. It has been reported that linolenic (LN, n-3) series 

FAs are also dietarily essential for tilapia, but the optimum ratio of n-6 to n-3 and its effect 

on growth and health is unknown. Thus, this study evaluated the effects of various 

combinations of dietary LA and LN on growth, blood cells, immune response and disease 

resistance of all-male hybrid tilapia (Oreochromis niloticus x O. aureus) to Streptococcus

iniae challenge. Results confirmed that either LA or LN alone at 1.0% of the diet meets the 

dietary essential FA requirement of hybrid tilapia. Linoleic acid alone, however, appeared to 

promote better growth than LN alone. Provided that the diet contained 0.5% LA or higher, 

dietary LN at levels ranging from 0.25 to 2% can be included in tilapia diet without affecting 

their performance.

Amino acid supplementation improves hybrid striped bass growth 

Hybrid striped bass grow better when fishmeal-free diets are supplemented with amino acids. 

When fishmeal in fish feed is replaced with plant proteins, fish performance often declines 

because of imbalances in essential nutrients and intestinal dysfunction caused by anti-
nutritional factors in plant ingredients like soybean meal. When ARS scientists at Stuttgart, 

Arkansas, used the concentrations and ratios of three essential amino acids found in hybrid 

striped bass muscle to supplement practical fishmeal-free soybean meal-based diets, superior 

fish growth and nutrient retention was achieved. Because the concentrations of amino acids 

used were higher than those currently targeted by feed mills, this information allows feed 

mills to formulate more efficient fishmeal-free, soybean-based diets for hybrid striped bass, 

thereby reducing production costs and dependence on ocean-derived protein ingredients.

Improving Health

Kaolinitic clay protects fish from columnaris disease 

Columnaris disease, caused by the bacterium Flavobacterium columnare, is a costly disease 

of many commercially grown fish species, including channel catfish. Despite its importance, 

few preventatives or therapies exist for this disease. In this study, a type of clay called kaolin 

was evaluated for the prevention of columnaris disease. ARS scientists in Stuttgart, 

Arkansas, demonstrated that addition of kaolin to the water significantly improved the 

survival of channel catfish that were experimentally challenged with the disease, and 

protected the gills from damage by the bacteria. Data suggests that kaolin works by binding 

to the bacteria, thereby preventing it from attaching to the fish and initiating disease. Kaolin 

is a novel, non-antibiotic treatment to increase survival rates in catfish hatcheries.

Copper sulfate effectively controls fungus on and increases survival of sunshine bass 

eggs 

Fungus in sunshine bass hatcheries can cause decreased hatch rates of bass eggs and decrease 

profits. A collaborative study with ARS scientists in Stuttgart, Arkansas, and Keo Fish Farm, 

Inc. (Keo, Arkansas) addressed sunshine bass egg mortality from fungal growth. This study 

determined the optimum concentration of copper sulfate needed to prevent fungus from 

destroying the eggs while allowing the hatched larvae to thrive. This finding has led to 

improved larval survival and reduced time and effort in the hatchery, having an immediate 

economic benefit to the farmer with this inexpensive treatment. The majority of the industry 

is now using this treatment.

New diagnostic test detects a serious bacterial disease of rainbow trout 

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

trout aquaculture. ARS researchers at Leetown, West Virginia, developed a highly sensitive 

polymerase chain reaction (PCR) assay to accurately measure small amounts of this pathogen 

in fish tissue. The test recognizes a unique gene sequence that is only found in F. 

psychrophilum. The assay successfully identified more than 200 different isolates collected 

from farms where fish suffered from the disease. The assay was used to quantify bacterial 

numbers in experimentally and naturally infected rainbow trout tissues. Assay protocol and 

DNA standard have been distributed to government and university fish health researchers to 

enhance efforts to detect and control bacterial cold water disease.
Survey of parasites associated with catfish aquaculture 

Mississippi State University scientists have conducted a survey of myxozoan parasites 

associated with catfish aquaculture. Myxozoan parasites have two distinct life stages, one 

stage in a worm host and another in a fish host, that until recently were thought to be 

unrelated parasites. Using molecular techniques, the stages of myxozoan parasite life cycles 

have been isolated and genetically characterized using molecular biology techniques. This 

survey has identified at least nine different myxozoan parasites in catfish ponds. In addition, 

two entire myxozoan life cycles have been molecularly confirmed, linking the parasite

released by the worm to the parasite found in the catfish. Moreover, this work has also 

identified and genetically characterized a previously undescribed myxozoan parasite from 

catfish, although the worm residing stage associated with this myxozoan has not been 

determined. The effects these previously uncharacterized myxozoan parasites have on 

catfish production is currently unknown and will be a focus of future research.

Disease outbreak linked to water chemistry 

Columnaris is a deadly fish disease that is caused by a bacteria (Flavo-bacterium columnare) 

that attaches to a fish's gills or skin (bacterial attachment). If we can stop the bacteria from 

attaching to the fish, we can prevent the fish from getting sick. Columnaris disease cannot be 

induced in some labs, and one possible explanation could be the water source. ARS 

scientists in Stuttgart, Arkansas, and Stoneville, Mississippi, found dramatic differences in 

catfish mortality after exposing fish to the columnaris bacteria in well-water from the two 

labs. Further investigation indicated bacterial attachment was 2000-fold less in softer waters 

with tannins. An additional study manipulated the calcium and tannin concentration in the 

waters to study their effects on the disease. The results suggest calcium is a key regulator of 

bacterial attachment. The study reveals the mechanisms of bacterial pathogenicity; this 

greater understanding will lead to further advances in controlling this disease.

Production Systems and Products

Development of an improved aerator for the catfish industry 

Supplemental aeration is used by all catfish producers and it is critical to maintain dissolved 

oxygen at levels that support high densities of catfish grown in production ponds, especially 

when oxygen levels drop on warm summer nights. Paddlewheel aerators have been used for 

aeration in aquaculture for over 30 years and while they transfer oxygen to the water 

efficiently, they also move a huge volume of water so the oxygen concentration increases 

slowly. Thus, a great deal of equipment and a large amount of power is required to prevent 

low DO (dissolved oxygen) 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. This invention has a patent application currently pending with the U.S. Patent and 

Trademark Office. Two commercial-scale PTA's were installed in an 8-acre catfish 

production pond and gave promising results. This new equipment will both lower energy 

costs and enable higher production densities.
Burrowing shrimp recruitment monitoring tool 

The burrowing activities of two species of shrimp cause shellfish to sink under the mud and 

die in West Coast estuaries. The aquaculture industry has addressed this problem by 

annually treating some of their beds with a pesticide, but are searching for alternative control 

measures and attempting to implement an integrated pest management program. ARS 

researchers in Newport, Oregon, discovered that shrimp population abundance can be traced 

to distinct years when shrimp pelagic larvae recruit to each estuary. Their abundance after 

settlement can be used to forecast the need for treatment of older shrimp on aquaculture beds, 

since adult shrimp don’t move. This accomplishment will enable researchers and producers 

to develop simple monitoring techniques that can be used to track recruitment and be adopted 

in their integrated pest management program.

Intensive production of hybrid catfish 

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

intensive production of hybrid catfish (a cross between channel catfish females and blue 

catfish males). Production of hybrids has reached over 20% of the catfish produced (nearly 

200 million juveniles per year, up from only a few million 5 years ago). Research has 

demonstrated that hybrid catfish can tolerate a slightly lower dissolved oxygen concentration 

than channel catfish. They also have better tolerance to common diseases affecting catfish, 

resulting in a greater feed intake through spring and fall when diseases are more common. 

Continued adoption of hybrid catfish by the industry is resulting in increased profits due to 

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

ratios.

Development of a heat exchanger for use in a commercial catfish hatchery 

At a local commercial catfish hatchery, a counter-current heat exchanger system was 

installed and reduced the non-renewable energy use by approximately 50%. This is 

equivalent to an estimated energy savings (operating cost) of $790 per day or $35,550 per 

season (45 days). Modifications to the original design should improve efficiency even more 

next hatching season.

Development of improved culture methods for fry and fingerling production 

Survival of fingerling catfish in nursery ponds is highly variable and averages between 50-

60% on most commercial operations. While disease is an important variable, fingerling 

survival is often poor in the absence of disease. Scientist from Mississippi State University

conducted pond studies to evaluate hatchery practices on growth and survival of catfish 

fingerlings. Channel catfish fry were transferred from the hatchery to nursery ponds at 

different developmental stages to reflect current industry practices. Fry were stocked before 

being fed a commercial fry diet (before or at the time of yolk sac absorption) or 4-7 days 

after being fed a commercial fry diet. Stocking fry in the early developmental stages resulted 

in poor survival. Since nursery ponds contained adequate zooplankton populations that serve 

as a food source, poor survival of early stocked fry was likely related to predation by aquatic 

insects. To increase fingerling survival fry should not be stocked in nursery ponds until they 

are fully developed and readily accept commercial diets. In a second study we found that 

there were no differences in fish production between fry nursery ponds that are fed 

commercial diets and ponds that rely on natural productivity for the first six weeks. Total kg 
of feed fed was significantly reduced in the delayed feed treatment, averaging 26 kg/pond 

less feed fed. If proper fertilization practices are implemented, large numbers of desirable 

zooplankton for catfish fry culture are attained, and these zooplankton are able to sustain 

catfish fry stocked up to 250,000/ha. Therefore, no commercial diets are required during the 

first 6 weeks of culture, saving over $95.55/ha in initial feed costs.

Carotenoid content in channel and hybrid catfish 

One problem for the catfish industry has been wide variation of fillet color, and some fillets 

have an unattractive yellow color thought to be caused by carotenoids in their diet. The 

objective of this study was to compare the most abundant carotenoids from channel and 

hybrid catfish. ARS scientists from the Southern Regional Research Center in New Orleans, 

Louisiana, collected fresh channel and hybrid catfish fillet samples from a commercial 

processor in Mississippi. Samples were freeze dried and then extracted with acetone; and 

carotenoids were identified using liquid chromatography/mass spectrometry (LC/MS) (Silica 

column, APPI). Two major carotenoids, lutein and zeaxanthin, were identified in both the 

channel and hybrid fillets, and the average content in channel catfish was higher than that in 

the hybrid fillets. This study identifies the major carotenoids in hybrid catfish, and will 

support efforts to standardize the color of catfish fillets.

Green water improves hybrid striped bass larval culture 

The availability of larval fish is critical for the successful development of aquaculture.

Aggressive behavior by the fastest growing fish and the need to provide an adequate quantity 

of food items are constraints to larval culture of hybrid striped bass. In a study using 

recirculating aquaculture technology, scientists at the Stuttgart National Aquaculture 

Research Center, Stuttgart, Arkansas, demonstrated that introducing algae into the culture 

water (green water) increased larval survival by more than 20% and decreased variation in 

individual fish size relative to those reared without the addition of algae (clear water). Green 

water reduced the ability of larger fish to locate and attack smaller fish and improved the 

ability of fish to find and consume food items. Increased larval survival of hybrid striped 

bass has been shown to reduce the cost of production by 10% for each 5% increase in 

survival, thereby resulting in more efficient utilization of culture facilities.