RESULTS AT A GLANCE...

"*"

The U.S. aquaculture industry continues to grow -- and with it the need for research and development of new technology to insure its future growth and success.

Projects developed and funded by the Southern Regional Aquaculture Center are based on industry needs and are designed to directly impact commercial aquaculture development in all states and territories. This program is acknowledged to be an unusually efficient and productive use of Federal funds.  Its efficiency lies in its unique approach to research in which problems are identified at the local level and then solved using a coordinated, team approach making use of the best scientific talent in the Southern Region.

Subject areas of SRAC projects have included:

Information transfer is an important part of the SRAC program as is evidenced by the large number of scientific and other articles published by participants in SRAC projects including:

Perhaps the most important measure of success is the extent to which the results of SRAC projects have influenced or improved domestic aquaculture. Results of SRAC projects are being widely adopted by the industry to reduce feed costs, to improve the shelf-life of aquaculture products, and to reduce the incidence of environment-derived off-flavors in pond-raised fish.

"*"

More details on the following projects can be found in the SRAC Annual Progress Reports and in the comprehensive listing of scientific articles produced from each project.

"*"

Publications, Videos and Computer Software
(See also SRAC Annual Progress Reports)

178 authors from across the United States have contributed to SRAC’s publication projects.

Ten fact sheets, one final project report, and one DVD were completed this year with five fact sheets and one PowerPoint presentation in progress.

Twenty-seven scientists from across the Southern Region contributed to publications completed by SRAC this year.

SRAC has now published 189 fact sheets and species profiles, 5 project summaries, 19 research publications, and 20 videos.

SRAC has now converted eight VHS videos to DVD format.
Titles of some recent SRAC publications:

Bait Shrimp Culture
Hard Clam Hatchery and Nursery Production
Components and Use of an In-Pond Fish Grading System
Species Profile: Florida Pompano
Procambarid Crawfish: Life History and Biology
Advances in Catfish Harvesting Gear: Seines and live cars
Species Profile: Hybrid Sunfish
Disease Prevention of Fish Farms

In the months from September 2006 through August 2007, more than 32,000 unique visitors came to the SRAC web site and accessed over 216,600 pages from the SRAC web site.

All fact sheets completed by this project to date are available on the Internet at <http://www.msstate.edu/dept/srac> and <http://srac.tamu.edu>.

"*"

Management of Environmentally-Derived Off-flavors
in Warmwater Fish Ponds
(See also SRAC Annual Progress Reports)

Low-phytate varieties of barley, corn and soybean meal elevate phosphorus availability to channel catfish so they may provide a dietary means of reducing phosphorus excretion as these feed stuffs become more readily available.
Of several treatments tried, the treatment that resulted in less phosphorus availability and phytoplankton abundance combined pond bottom drying and tilling with gypsum application to the pond.

A bacterium isolated from pond water selectively attacks odor-producing blue-green algae while having no effect on beneficial algae or catfish. The bacterium shows promise as a biological control agent for the algae that cause off-flavors.
Weekly, low-level treatments of catfish ponds with copper sulfate reduced the incidence of off-flavor by 80% and increased net revenues by over 40% compared to untreated ponds.

"*"

Optimizing Nutrient Utilization and Reducing Waste
Through Diet Composition and Feeding Strategies
(See also SRAC Annual Progress Reports)

The crude protein level in catfish feeds can be reduced to at least 28% without affecting fish production. Reduced protein levels in feeds will reduce feed costs and improve protein utilization.
Catfish feeds with all-plant protein can be used without affecting fish production. The cost of feeds with all-plant ingredients is about 5% less than traditional feeds.
Catfish being grown to food-size should be fed daily during the growing season for maximum production.
Reducing feeding frequency from three or four times a day to two times a day can save costs when raising hybrid striped bass fingerlings.  Feeding food-sized hybrid striped bass once a day in early morning or late afternoon results in best growth, feed conversion, and uniformity of size.
Feeding supplemental feeds to crawfish during the harvest season reduces the catch, probably by decreasing the appeal of bait in the traps.

"*"

Verification of Recommended Management Practices
for Major Aquatic Species
(See also SRAC Annual Progress Reports
and UAPB Catfish Yield Verification Program)

Analysis of the production and economic data indicate that the recommended management practices result in greater profit to the producers.
Good feeding practices resulted in feed conversion values below 1.6:1.
These results demonstrate the importance of careful feeding and the positive effect feed management has on profitability.

"*"

Control of Blue-green Algae in Aquaculture Ponds
(See also SRAC Annual Progress Reports)

A derivative of a natural compound found in certain plants is undergoing patent application for use as a selective algicide to help prevent musty off-flavor in farm-raised catfish.
Studies in Mississippi and Alabama indicate that various manipulations of waterborne plant nutrients have little promise for controlling phytoplankton community composition in catfish ponds with high feeding rates.
Phosphorus-only fertilization was as effective as nitrogen plus phosphorus fertilization in bait minnow ponds. Phosphorus-only fertilization is less expensive, conserves nitrogen, and lessens the possibility for nitrogen pollution of natural waters by pond effluents. Removal of soft sediment from old (25+ years) bait minnow ponds should improve bottom soil quality.
No benefit was found from using sodium nitrate to suppress phosphorus release from pond sediments.
Pond renovation had little effect on subsequent levels of soluble reactive phosphorus in baitfish pond waters or on average concentrations of phosphorus in bottom sediments. A possible explanation for these results is that pond bottom soils are used to rebuild levees during renovation and not removed from ponds. Bottom soils are mixed in the pond reconstruction process, and renovation decreased the average soil phosphorus concentration in the upper 2-cm of sediment.
Artificial daytime water circulation of hybrid striped bass ponds had no effect on the incidence of blue-green algae in the phytoplankton community and did not measurably improve water quality.
In both Alabama and Georgia, stocking threadfin shad with channel catfish resulted in lower ammonia and nitrite levels late in the growing season. The improved environmental conditions apparently resulted in significantly better survival of catfish in the presence of shad in the Alabama study.
Polyculture of threadfin shad with channel catfish in relatively small experimental ponds resulted in improved water quality conditions and enhanced catfish survival. The stocking of threadfin shad, in four commercial channel catfish ponds in West Alabama, did not result in improved water quality when compared to four similar ponds with catfish, but no threadfin.
Blue-green algae numbers were reduced by threadfin shad over a three-year period in intensively-managed catfish ponds.
Early spring stocking of only 150-200 tilapia "breeding pairs" per acre into PAS units allows for a minimum cost control of late season blue-green algal dominance allowing for catfish harvest during a "window" of reduced fish off-flavor. This technique promotes acceptable PAS water quality limits supporting observed net catfish productions in 1999-2001 of 11,500 to 17,200 pounds /acre with a tilapia co-production of 2,400 to 5,400 pounds/acre.

"*"

Management of Aquacultural Effluents from Ponds
(See also SRAC Annual Progress Reports)

Treatment of the final 20% of water discharged when ponds are drained can be accomplished with sedimentation basins designed with a hydraulic retention time of 8 hours. However, a settling time of 2 to 4 hours is sufficient to reduce total suspended solids in effluents to 75 to 90% of original concentrations.
Effluent volume can be reduced by increasing pond depth to increase rainwater storage capacity and linking the combined storage/production pond to one or three adjacent conventional ponds. Effluent volume was reduced by more than 50% and groundwater consumption was reduced by more than 40% compared to conventionally managed ponds. Linking ponds and reusing stored water has not affected fish growth, occurrence of diseases, or water quality.

"*"

Characterization of Finfish and Shellfish Aquaculture Effluents
(See also Final Project Report No. 600, RAC RESULTS and SRAC Annual Progress Reports).

The results of this project suggest that the impact of aquaculture pond effluents on the environment can be reduced by following some or all of the following management practices:

Use high quality feeds and efficient feeding practices.
Provide adequate aeration and circulation of pond water.
Minimize water exchange.
Operate ponds for several years without draining.
Capture rainfall to reduce pond overflow.
Allow solids to settle before discharging water.
Reuse water that is drained from ponds.
Optimize watershed areas.
Treat effluents by using constructed wetlands.
Use effluents to irrigate terrestrial crops.

"*"

Food Safety and Sanitation of Aquaculture Products:  Microbial
(See also RAC RESULTS and SRAC Annual Progress Reports)

The results of this project reveal that cultured fish represent one of the safest sources of muscle protein and related nutrients among all muscle foods produced in the United States. The development of HACCP (Hazard Analysis Critical Control Point) audit procedures has become an important quality assurance tool which ensures product quality and consumer safety. Improved and newly-developed modified atmosphere packaging (MAP) techniques have been implemented in commercial processing which have increased the shelf-life of many aquaculture products. Approximately 100 published articles from these research studies include valuable information on processing, temperature control, spoilage, purchasing, storage, handling, and preparation of aquaculture products.

"*"

Development of Improved Harvesting, Grading and
Transport Technology for Finfish Aquaculture
(See also SRAC Annual Progress Reports)

A new seine technology that is currently being commercialized improves efficienty of catch, improves grading, and reduces seine time.
An efficient in-pond fish grading system has been developed specifically for fingerlings, stockers, fooded-sized and brooder-sized channel catfish.
Modifications of the catfish grader improved grading of both fingerling and adult hybrid striped bass.
Anesthetics help alleviate stress during transport of ornamental fish and should have applications to transport of other species.
The in-pond, platform fish grader is a profitable short- and long-term investment for all sizes of farms.  The major economic benefit results from returning sub-marketable fish to the pond for additional growth.

"*"

Identification, Characterization, and Evaluation of Mechanisms of
Control of Bolbophorus-like Trematodes and Flavobacterium columnare-like
Bacteria Causing Disease in Warm Water Fish
(See also SRAC Annual Progress Reports)

Studies on the various life stages of Bolbophorus damnificus have revealed that the adult trematode resides in the gut of the American white pelican. The parasite has not been found in wild cormorants, great egrets, great blue herons, snowy egrets, cattle egrets, green herons, belted kingfishers and little blue herons. Attempts to artificially infect cormorants, great blue herons and great egrets failed.
The presence of fully developed Bolbophorus metacercariae does not affect growth or health of catfish. The deleterious effects of this infectious agent are therefore associated with penetration of the parasite and initial stages of encystment.
Mild, sub-lethal trematode infections can significantly reduce catfish growth by reducing feed consumption and increasing mortality associated with concurrent bacterial infections.
A shoreline treatment with slurried hydrated lime applied in a 3-foot swath at 100 pounds of lime per 100 feet of shoreline reduced snail populations by over 95%.
A low-dose, full-pond treatment with copper sulfate was developed that safely eradicates the trematode's intermediate host -- the ram's horn snail.
Ponds stocked with redear sunfish had significantly fewer snails than ponds without sunfish. Redear sunfish preferentially consumed snails and chironomids when available even when trained on pelleted diets prior to stocking ponds.
Selective cytophaga agar SCA has performed the best as a primary isolation medium in preliminary tests in isolation of Flavobacterium columnare from contaminated sites such as the gills and skin. For maintenance following isolation, tryptone yeast extract TYE medium as a moist slant, held cultures viable for as long as 84 days. For large batch broth culture, FCGM outperforms other formulations tested.
An improved medium has been developed for antimicrobial susceptibility testing of Flavobacterium columnare.
Molecular (PCR) and conventional (API system) methods may be used for the identification of F. columnare. Molecular methods such as ribotyping, RAPD analysis, and sequencing of the intergenic spacer region between the 16S-23S ribosomal RNA genes can allow for discrimination between different genotypic strains.

"*"

Innovative Technologies and Methodologies for Commercial-Scale Pond Aquaculture
(See also SRAC Annual Progress Reports)

In 2005 and 2006, channel catfish fry were stocked into 6.5-m3 Clemson PAS cells equipped with adjustable depth net-pens with feed applied with automated feeders for a period of 120 to 148 days. After 4 months of growth fingerlings were harvesting at average sizes ranging from 122 to 158 g each in 2005, and 117 to 139 g each in 2006. Additional growth trials are currently underway (in 2007) to determine average fingerling harvest size at maximum projected carrying capacity of 6,700 to 8,400 kg/ha.

An “extensive” PAS system used in Mississippi can be constructed by modifying existing earthen ponds. Net annual fish production in the system has ranged from 17,000 to almost 20,000 kg/ha (15,000 to 18,000 pounds/acre) at feed conversion ratios less than 2.0.

Indicators of the efficiency of resource use in aquaculture have been developed and are being used by several environmental advocacy groups in assessing the sustainability of aquacultural production. Direct energy use for production of channel catfish in Alabama was 3.059 kW · hr/kg with 44% of energy used on farms.

Detailed cash flow budgets have been developed in this project for both existing and new startup catfish farms under a variety of equity positions. These budgets measure the amount of cash flow risk for varying farm sizes with different levels of financing and for management strategies involving fingerlings only or a mix of fingerling and stockers for growout production.

"*"

Improving Reproductive Efficiency to Produce Channel × Blue Hybrid Catfish Fry
(See also SRAC Annual Progress Reports)

A water temperature of 21°C is the minimal temperature needed to initiate the reproductive process in channel catfish. Tracking degree-days above 21°C may be useful as a management tool to predict channel catfish spawning times and will be especially useful as a tool to predict best times to initiate artificial spawning for hybrid embryo production.

Early spawning can be accomplished by heating water prior to the natural spawning season without any difference in success compared to the natural spawning season. When 100 degree-hours are reached ovulation and fertilization should be successful. If warm water is available, channel catfish can be successfully spawned in early January.

Feeding standard 32% protein floating catfish feed 6 times per week for 2 months prior to spawning gives equal or better fry production compared to high protein diets. Supplementation of broodfish diets with menhaden fish oil, DHA and ARA 2 months prior to spawning can increase hybrid fry output up to 100% if the fish were poorly prepared up to that point of time. If the fish are in excellent condition, the fatty acid supplementation is not necessary. Supplementation of brood stock diets with the feeding of forage fish to channel catfish females, does not greatly impact hybrid fry production, but has strong positive effects on sperm production in blue catfish males.

Using the appropriate genetic line of channel catfish female can double or triple hybrid fry output. Strain of blue catfish male has important effects on sperm production and hatching rate of hybrid embryos.

Hatching rate of hybrid embryos is improved if LHRH-injected channel catfish females are stripped within 2 hours of first observation of egg release. Waiting longer will increase the number of eggs stripped, but this is more than offset by much lower hatch rate.

Brood stock age is important for spawning success. Other indicators of spawning success are broodfish weight, length, and ratios of body proportions. Broodfish having a width (cm)/weight (kg) ratio of  less than 4 have a high spawning success rate. To obtain the best success in induced spawning to produce hybrids, broodfish should be 5 years old, with a weight of over 3 kg (6 to 7 pounds), and a length greater than 60 cm (24 inches).

The dose of 100 µg/kg LHRHa implants results in the most consistent hybrid fry production. At the end of the spawning season this dose needs to be reduced to 75 µg/kg.

Water activated, but unfertilized, eggs showed the characteristic movements seen previously in normally fertilized embryos. Blastodisc enlargement and protrusion also took place mimicking normal development, however, none of the activated, unfertilized eggs underwent gastrulation or cleavage.

Ultrasound may be used to ascertain ovulation in channel catfish females and the appropriate time for stripping of eggs. Spectrophotometric assays can be used to determine sperm concentrations from crushed testis of catfish. Utilization of these tools should result in more efficient use of sperm and more consistent fertilization rates.

Sperm concentrations can be reduced in currently used fertilization protocols by 100-fold with little reduction in subsequent hatch rate. This should result in much more efficient use of male broodfish when producing hybrid catfish.

The frequency of formalin treatments should be three per day to maximize hatch rate of hybrid embryos. Four treatments per day is excessive. At 28°C, hybrid embryos are chemically sensitive to formalin between 42 to 46 hours postfertilization, and formalin treatments should be avoided during this period.


"*"

Feed Formulation and Feeding Strategies for Bait and Ornamental Fish
(See also SRAC Annual Progress Reports)

Stocking juvenile golden shiners in late July resulted in lower single-season yields of jumbos when compared to direct stocking of hatchery fry at low densities. However, the extra production of jumbos produced by stocking fry must be balanced against other uses for the ponds. Growout diets with no fish meal fed once daily to golden shiners supported yields similar to those obtained with more expensive diets and more frequent feeding.

Prebiotics, immune stimulants, and differences in protein or lipid content of diets had only limited impacts on general performance of golden shiner. However, the prebiotic GroBiotic-A® significantly improved survival of golden shiner exposed to the bacterium that causes columnaris disease. In subsequent trials in systems with natural foods (pools or ponds), it was necessary to impose a stressor (crowding) on golden shiners before exposure to bacteria to get a statistically significant increase in survival of fish fed diets with prebiotics. Prophylactic use of the prebiotic should be economically feasible based on a partial budget analysis of data from the golden shiner pond trial. GroBiotic-A® also enhanced growth of goldfish in an outdoor system, indicating potential in other baitfish.

Zebra danios, Swordtails, Plecostomus and Firemouth Meeki Cichlids performed similarly on processed or non-processed diets in ponds, while results were generally less favorable for liquid fertilizer or cottonseed meal treatments. Except for zebrafish, these species also performed similarly on processed and non-processed diets in aquaria.

 

"*"

· Top this page · Home · What's New · The RACs · About SRAC · Our Region · Directories · Manual;Forms
· SRAC Projects · Progress Reports · Final Reports · Publications · Associations · Links