• Introduction
• Genetic Improvement
• Growth, Development, and Nutrition
• Aquaculture Production Systems
• Sustainability and Environmental Compatibility of Aquaculture
• Quality, Safety, and Variety of Aquaculture Products for Consumers

Introduction

The Agricultural Research Service (ARS) Aquaculture National Program expanded in four of the six research program component areas:  Genetic Improvement; Integrated Aquatic Animal Health Management; Aquaculture Production Systems; and Sustainability and Environmental Compatibility of Aquaculture.

Dr. Henry (Hank) Parker returned to the National Program Staff in April 2001, after detail assignments as Acting Director, U.S. Horticultural Research Laboratory, Fort Pierce, Florida, and Acting Associate Area Director, ARS North Atlantic Area.  Dr. Lewis (Lew) Smith served as Acting National Program Leader for Aquaculture while Dr. Parker was on detail assignment.

Several significant activities occurred during this reporting period.  On August 31, 2001, Senator Robert C. Byrd dedicated the new National Center for Cool and Cold Water Aquaculture (NCCCWA) in Leetown, West Virginia, and was the keynote speaker for the dedication ceremony.  The Center also held a programplanning workshop with customers, stakeholders, and research partners on October 1819, 2001. 

On March 57, 2001, ARS and the Oceanic Institute cohosted a workshop, "BiotechnologyAquaculture Interface:  The Site of Maximum Impact" in Shepherdstown, West Virginia.  The workshop report and related information are available at http://nps.ars.usda.gov/static/arsoibiotecws2001. 

With new Congressional funding in fiscal year (FY) 2001, ARS initiated program planning and design phases for a new ARS National Cold Water Marine Aquaculture Center to be constructed in Orono and Franklin, Maine, in cooperation with the University of Maine.  On April 2627, 2001, ARS held a program planning workshop in Orono with customers, stakeholders, and aquaculture scientists to obtain input into the research programs, target species, and identify facility requirements of the new Center. 

With new Congressional funding in FY 2001, ARS also initiated aquaculture research programs with the Canaan Valley Institute, Davis, West Virginia; the Harbor Branch Oceanographic Institution, Ft. Pierce, Florida; and the University of Connecticut. 

The public investments in ARS aquaculture research are reaping important dividends, exemplified by the following selected accomplishments, by program component area, during FY 2001: 

Significant Accomplishments by Component

Genetic Improvement 

Since there has been limited genetic improvement of aquaculture stocks, there are major opportunities for improvement through traditional animal breeding, broodstock development, germplasm preservation, molecular genetics, and allied technologies.  ARS research addresses improvement of growth rates, feed efficiency, survival, disease resistance, fecundity, yield, and product quality; genetic characterization and gene mapping; and conservation and utilization of important aquatic germplasm. 

Genetic mapping of rainbow trout.  Microsatellites are genetic markers that are used to locate genes affecting traits of importance to enhance aquaculture production, for example growth and disease resistance.  ARS scientists at the NCCCWA, Leetown, West Virginia, are developing these markers for genetic mapping in rainbow trout.  Using molecular technology, 128 microsatellite markers were identified and genetic analysis revealed that they demonstrated variation in different strains of rainbow trout.  These markers will be useful in localizing economically important traits to a region of a chromosome in rainbow trout. 

Genetically improved catfish line.  Scientists in the applied catfish breeding program at the ARS Catfish Genetics Research Unit (CGRU), Stoneville, Mississippi, developed a genetically improved catfish line, USDA103, with improved growth and feed consumption.  From the 1998 and 1999 spawning seasons, over 1.7 million USDA103 line catfish fry were supplied to Mississippi State University for stocking into earthen ponds at the Thad Cochran National Warmwater Aquaculture Center, and released as NWAC103 line catfish to 34 commercial producers from 5 states in 10,000 pound lots beginning in February 2001.  Results of experimental trials demonstrated that USDA103 catfish should produce marketable catfish faster than fish currently cultured following recommended management guidelines.  Economic analyses conducted by Mississippi State University economists project $83 million in increased value if USDA103 catfish were raised in Mississippi instead of the present lines of catfish.

DNA markers for catfish identification.  Identification of catfish families and populations is difficult due to the similar physical characteristics of all channel catfish.  Genomic DNA from channel catfish was sequenced at the ARS CGRU, Stoneville, Mississippi, in order to identify useful molecular markers.  Researchers identified and characterized 313 polymorphic DNA markers, termed microsatellites, in the channel catfish genome and made them commercially available through ResGen (Huntsville, Alabama).  These markers will allow breeders to identify the USDA103 strain of catfish, and the commercially available markers will allow scientists and breeders to identify other families and strains of catfish. 

Genetic control of catfish growth.  Significant advances have been made in channel catfish nutrition, reproduction, and disease research over the past 30 years; however, the mechanisms controlling catfish growth have received little attention.  Researchers at the ARS CGRU, Stoneville, Mississippi, isolated and sequenced a gene from catfish brain tissue that produces two important growth_regulating peptide hormones.  It was shown, for the first time in any fish, that this gene is active in skeletal muscle and fat, indicating that these peptides are also likely involved in the control of fillet yield and body composition.  Characterization of this gene provides an important tool that will lead to improved techniques for selection of superior growing lines of channel catfish for the aquaculture industry. 

Integrated Aquatic Animal Health Management 

Despite progress in aquatic animal health, significant losses to diseases still occur.  ARS research addresses improvement of survival, growth, vigor, and wellbeing of cultivated aquatic animal stocks through integrated aquatic animal health research; improved technologies and practices, such as population health management; and development of health management products, including vaccines and therapeutics, and disease detection/diagnostic techniques. 

Combating Streptococcus iniae.  ARS scientists at the Aquatic Animal Health Research Unit (AAHRU), Auburn, Alabama, developed a successful modified killed Streptococcus iniae vaccine to prevent streptococcal disease in tilapia and hybrid striped bass.  The vaccine was patented in 2001.  The scientists have also established that the nares are an important route of infection for S. iniae and that antibody is important in protecting fish from streptococcal disease.  Other significant accomplishments include the establishment of tissue culture methods to examine the effects of toxins and stressors on fish immune function.  These tools will improve understanding of immunity and disease resistance in fish. 

Dietary effects on fish health.  Scientists at the ARS AAHRU, Auburn, Alabama, are conducting research on the role of diet in improving fish health and resistance to disease.  They found that a dietary level of folic acid had no effect on the resistance of tilapia to Streptococcus iniae infection, but a level of 0.5 to 1.0mg/kg diet is needed for maximum growth.  They also determined that inositol is not required by tilapia for growth but supplementation of this vitamin decreased tissue lipid deposition.  Total replacement of soybean meal by cottonseed meal reduced the nutritional value of diet for tilapia but improved the nonspecific immune response.  However, this did not improve protection against Streptococcus iniae infection.  Autoclaving (dry cycle) of raw soybean meal for 40 minutes improved its nutritional value comparable to that of commercial soybean meal, but reduced antibody titer and resistance of channel catfish against ESC (Enteric Septicemia of Catfish) disease.  Gossypol acetate at 300 ppm in the diet decreased the growth performance of channel catfish (a previous study reported that a level of 900 ppm was toxic to channel catfish).  Feeding catfish diets containing gossypol tended to improve nonspecific immunity. 

Copper sulfate an effective treatment for Ram's Horn Snail.  ARS scientists at the Harry K. Dupree Stuttgart (Arkansas) National Aquaculture Research Center (SNARC) are conducting research conducted directed toward gaining either Food and Drug Administration (FDA) or Environmental Protection Agency (EPA) approval of new chemicals and drugs for disease control in the culture of food fish.  In conjunction with research on the effectiveness and safety of using copper sulfate for snail control they developed an effective copper sulfate treatment for control of the Ram's Horn Snail.  This snail is the principal vector for trematode infections in fish in commercial catfish and bait fish farms.  The chemical has been registered for use as a pesticide by EPA (Registration No. 12788) and is currently in use on commercial fish farms.  

Growth, Development, and Nutrition 

There are substantial opportunities to improve the growth, development, and nutrition of cultivated aquatic organisms.  ARS research addresses improving survival, growth rates, feed conversion, environmental tolerances, and feed formulations and feeding strategies to reduce dependence on marine fishbased protein in aquaculture diets. 

Grainbased fish diets.  In order to obtain stocks of rainbow trout enhanced for their ability to grow on a diet highly supplemented with cereal grains, an ARS scientist at the Small Grains and Potato Germplasm Research Unit, Aberdeen, Idaho, carried out selective male by female crosses of four separate strains of rainbow trout.  Discrete family units were maintained for rearing on a modified cereal grain fish diet.  Isolated families from these controlled strain crosses have been reared on a cereal grain based diet alongside representative control groups reared on a standard commercial diet.  Three of the strains have finished their 130day selection period and have been sorted into separate distinguishable groups based on growth, feed digestibility, immunological response, and feed conversion ratios.  These initially improved stocks may be used to continue genetic enhancement of stocks, generation of broodstock for the production of improved stock, and for the screening of molecular markers in order to delineate precise molecular indicators that might be useful in markerassisted selection breeding programs.  Improvement in any of these areas will prove invaluable in lowering feed costs, reducing aquaculture pollution, and increasing market potential for locally produced crops.  

Proteolytic enzymes from fish processing byproducts.  An ARS scientist stationed in Alaska is working with scientists from the University of Alaska to develop aquaculture and livestock feed supplements from fish processing wastes.  In conjunction with this project, scientists at the Fishery Industrial Technology Center, University of Alaska, Fairbanks, are attempting to identify proteolytic enzymes, including collagenases, other proteases, and lipases derived from processing by_products of Alaskan whitefish.  These enzymes could be used to help degrade fish skins, including salmon ovarian skins.  The scientists collected wash water from Arrowtooth flounder (Atheresthes stomias) processing and cod (Gadus macrocephalus) stomachs from local processing plants to test for collagenases.  After determining the appropriate conditions for using fish skin to test for collagenase activity they found evidence for significant heat_activated proteolytic enzyme activity from Arrowtooth flounder washings; however, they determined that the activity was not due to a collagenase.  On the other hand, they did find relatively high collagenase activity in the stomach tissues of G. macrocephalus.  The activity in cod stomachs is sufficiently high that a crude extract of cod stomachs can probably be employed to reduce the tensile strength of salmon ovarian skins. 

Optimizing soluble protein concentration in fish meal production.  Scientists at the University of Idaho and the Fisheries Industry Technology Center, University of Alaska, Fairbanks, are conducting research to determine the optimum proportion of soluble and structural proteins in fish meal produced by the traditional wet rendering process (separation of presscake and soluble protein) for use in feeds for aquatic animals.  They produced experimental batches of fish meals containing a range of soluble protein, from 0 percent to 40 percent of total protein in the fish meals, and evaluated these in experimental feeding trials with rainbow trout.  They found that the best growth was obtained at 20 percent soluble protein, but that the best feed/gain ratio was obtained at 0 percent solubles, most likely the result of leaching of soluble protein from feed pellets.  This information will guide Alaskan fish meal producers who are attempting to produce highvalue fish meal from Alaskan seafood waste using conventional fish meal plants, e.g., wet reduction. 

Aquaculture Production Systems 

There are opportunities to improve the performance of aquaculture production systems through development and application of innovative engineering approaches and technologies.  ARS research addresses development and successful application to aquaculture of new technologies as well as relevant existing technologies and engineering presently employed in other sectors of the economy. 

Reducing bird predation.  Doublecrested cormorant predation on cultured fish may cause major economic losses for the aquaculture industry.  ARS scientists at the SNARC evaluated the avoidance effectiveness of a physical bird predator barrier, modified to minimize cost, labor, and setup/takedown time.  Tests were conducted at a largescale catfish production facility in Southeastern Arkansas.  Overall, the modified physical barrier significantly limited doublecrested cormorant access to the ponds.  This easytosetup apparatus should greatly reduce losses of cultured fish to doublecrested cormorants. 

Sustainable shrimp production systems.  There is an opportunity to develop sustainable shrimp production systems that maximize shrimp productivity and performance and minimize environmental impacts.  Scientists at the Oceanic Institute, Waimanalo, Hawaii, conducted a tenweek growth trial under conditions of high stocking density, zerowater exchange, and high incidence of sunlight, with control of alkalinity and suspended particulate matter (by use of a beadfilter).  Successful higher density rearing in highly eutrophic zerowater exchange systems was achieved through better understanding of the interactions of culture water quality (biological oxygen demand, alkalinity, suspended particulate matter), microbial succession patterns, and shrimp growth and health.  This information will be useful in designing and operating shrimp culture systems that have high productivity and low environmental impact, and which, due to their low water requirements, may be sited in areas that are not currently available.

Increased aeration and improved water quality management increase catfish production and reduce off_flavor.  Scientists at the ARS Thad Cochran Warmwater Aquaculture Research Center, Stoneville, Mississippi, evaluated the potential of increasing catfish production, and reducing offflavor, using increased aeration, stocking and feeding rates.  Research was conducted in six ponds at the CGRU, Stoneville, Mississippi.  The results showed that production could be more than doubled through increased aeration and water quality management, while the incidence of offflavor was reduced by over 50 percent.  

Sustainability and Environmental Compatibility of Aquaculture 

The overall goal of ARS research in this area is to protect and conserve the nation's water resources and natural environments by conducting research and technology transfer to improve the sustainability and environmental compatibility of aquaculture production systems. 

Reducing waste discharges from aquaculture ponds.  The EPA is currently developing nationally applicable discharge standards for aquaculture.  Scientists at the CGRU, Stoneville, Mississippi, conducted a study to assess quality of pond effluents when ponds are drained and to determine the magnitude of "instream" processing of wastes discharged from ponds.  When ponds are drained, the initial flush of discharged water consists of pond water and a slurry of sediment that has accumulated around the drain structure inside the pond.  The initial discharge is, therefore, very high in solids, oxygen demand, and nutrients.  However, 510 minutes after the initial discharge, the effluent quality is identical to the bulk pond water for the remainder of the draining period.  Therefore, a significant fraction of the total material released when a pond is drained is discharged with the first few percent of the total water volume.  However, that material is associated with a relative heavy solids fraction and all of the material is removed by settling within 200 meters as the effluent flows through vegetated drainage ditches. 

Sustainable production systems.  Expansion of aquaculture is significantly constrained by the interaction of production systems with the external environment through biological and nutrient exchanges.  Scientists at the Freshwater Institute designed and evaluated sustainable cool and cold water finfish production systems that utilize intensive production technologies and water recycling.  Production system technologies were developed that minimize environmental interactions and biological exchanges through water recirculation, improved environmental control, and biosecurity management.  Domestic and international commercial fish farm operations producing Atlantic salmon smolts, Arctic char, ornamental fish, tilapia, rainbow trout, walleye, yellow perch, and hybrid striped bass have adopted these production systems designs and developed management strategies based on research results from this project. 

Managing aquaculture wastes.  There is a need to develop a protocol for a landbased aquaculture solids management system that minimizes leaching of nutrients to the surface water environment and is less resource intense than standard composting technology.  Scientists at the NCCCWA, Leetown, West Virginia, in cooperation with the Freshwater Institute, evaluated a carbon management strategy to minimize nutrient loss to the environment.  To do this, they compared one protocol of adding fish manure and a carbon source in amounts to maintain a constant carbon to nitrogen (C:N) ratio of 30 with another protocol of adding larger batches of carbon initially to establish a shortterm C:N gradient of up to 60, and then decreasing the ratio to about 30 after 8 applications of manure had been mixed in over time.  They determined the N and P sequestration and stabilization of the generated compost from each protocol.  They found that the initial higher C:N ratio treatment did not increase nutrient retention or stabilization of the compost.  Further, alternately layering the carbon source and manure appeared to be a satisfactory system to scale up the technology.  These results indicated that a layered cool compost system may be a viable manure management system to replace offline settling basins for fish farmers. 

Quality, Safety, and Variety of Aquaculture Products for Consumers 

The overall goal of ARS research in this area is to improve the quality, safety, and variety of aquaculture products through research and technology transfer.  ARS research addresses improvement of the safety, freshness, flavor, texture, taste, nutritional characteristics, and shelf life of cultivated fish and shellfish, and development of new valueadded products and processes. 

Monitoring and prevention of algal toxins.  Since 1999, algal toxins have been implicated in a total of 5 million pounds of channel catfish mortality, with a farm gate value of $3.5 million.  In collaboration with the University of Arkansas at Pine Bluff (UAPB) Aquaculture/Fisheries Center of Excellence, ARS scientists at the Aquaculture Systems Research Unit, Pine Bluff, Arkansas, experimentally exposed channel catfish to two commercially available cyanobacterial toxins and monitored over 100 commercial channel catfish ponds for the presence of potentially toxin producing cyanobacteria.  The laboratory studies demonstrated that the microcystinLR toxin was not highly toxic to channel catfish as initially proposed, and was probably not the toxin responsible for observed channel catfish mortalities.  The pond monitoring program prevented algal toxinrelated mortalities of channel catfish in the monitored ponds.  As a result of this work an algal toxicosis monitoring and prevention program has been successfully implemented by the UAPB Aquaculture/Fisheries Center of Excellence. 

Diuron effectiveness as a management tool to control off_flavor in catfish.  Diuron has been temporarily approved by the EPA for use in commercial catfish ponds to control offflavor produced by bluegreen algae; however, little information exists on its effectiveness.  Research by scientists in the ARS CGRU, Stoneville, Mississippi, the ARS Southern Regional Research Center (SRRC), New Orleans, Louisiana, and the Mississippi Agricultural and Forestry Experiment Station provided information on the effectiveness of this herbicide.  Fifteen oneacre ponds stocked with oneyear old fish were studied to determine if weekly diuron treatments improved catfish flavor.  Weekly samples were made for catfish flavor along with total production at the end of the study.  Research demonstrated that ponds treated with diuron had reduced incidence of offflavor and no decrease in fish production.  This information will be useful to decisionmakers considering whether to continue the use of diuron as a management tool to control offflavor in the catfish industry.

Molecular markers to identify problem algae.  Towards development of molecular markers for the identification of microorganisms (e.g. algae) with the potential for producing offflavor compounds, scientists at the ARS SRRC, New Orleans, Louisiana, developed and applied a nonbiased method of devising molecular markers (AFLP: amplified fragment length polymorphism).  Genomic deoxyribonucleic acid (DNA) from known microorganismal species in catfish aquaculture from Stoneville, Mississippi, has been isolated and is being used successfully in AFLP.  AFLP on a very problematic species, Pseudoanabaena, has yielded approximately fifty candidate molecular markers.  This project will produce a molecular assay capable of determining relative populations of all microorganisms in the catfish pond in less than an hour with portable instrumentation.