Improving Production Efficiency and Product Quality and Safety of Aquaculture Species

NON-TECHNICAL SUMMARY: Louisiana supports one of the most diverse aquaculture industries in the U.S. being the nations leader in crawfish and alligator production. The states oyster industry suffered significant losses due to the hurricanes of 2005. New technologies are needed to address the many concerns related to maintaining these and other viable aquaculture industries within the state. Crawfish reproduction and survival rates are highly variable in female broodstock and can be affected by a number of factors, which need assessment. Alligator meat is experiencing market expansion and methods are needed to improve shelf-life and food safety of these products. Although catfish production is declining within the state, development of new technology to stimulate advances in genetic improvement could spark a resurgence of this species. New and emerging species such as coppernose bluegill may offer alternatives to catfish production and development. Perkinsus marinus, a protozoan parasite of eastern oysters, causes extensive mortality each year. Evaluation of an off-bottom culture system that facilitates daily air exposure may minimize Dermo while increasing oyster shelf-life and safety. Finally, demonstrating that increased consumption of marine finfish and shellfish will decrease macular degeneration (the leading cause of blindness) would be a significant benefit to human health. <P>
PROGRESS: 2007/01 TO 2007/12<BR>
This is a new project that was only active for a few months during the reporting period, thus most of the research will occur during 2008 and few outputs occurred. Results from the crawfish component project were published in two popular press, one Southern Regional Aquaculture Center publication, and one FAO publication. <P>IMPACT: 2007/01 TO 2007/12<BR>
<OL> <LI> Mature female crawfish were placed in artificial burrows for observation of spawning following various treatments within the pond. Preliminary results indicated mortality from crawfish collected from overcrowded populations during burrow occupation was 47% greater and spawning rate was 74% lower than crawfish collected from a non-stunted populations. Crawfish allowed to forage in a food-rich rice field for 1 week prior to entering the artificial burrows showed reduced mortality and increased spawning rate. <LI>Thermostatic controllers for outdoor tanks have been designed, installed, and tested with and without a temporary greenhouse enclosure. The tanks have been stocked with channel catfish broodstock and are receiving heated water. Natural spawning will be monitored in the tanks and induced spawning will occur in the hatchery in late winter and the experiment repeated in spring. The tanks will be compared to spawning in heated and ambient temperature ponds at the same times. <LI>Juvenile coppernose bluegill will be stocked in ponds in spring for a one-year production trial. Four dietary treatments will be evaluated to determine the optimum level of dietary protein. Ponds will be batch-harvested and fish compared for growth, carcass characteristics and costs of production. <LI>Seed oysters (3,000) 20-30 mm in length were placed in culture bags (100 per bag) and suspended on an off-bottom adjustable long line system. Bags are being exposed to air daily to control overset and fouling. These oysters will be divided into three sampling-time sets and each set divided into five groups. Four groups will be continuously immersed for 2, 4, 8 or 12 weeks prior to harvest while the fifth group will continue to be exposed daily to air prior to harvest. At harvest, oysters from each group will be sampled to compare oyster mortality, shell heights, fouling, number of P. marinus parasites, V. vulnificus and V. parahaemolyticus loads, condition index and refrigerated shelf life. <LI>Coating alligator meats with a high molecular weight (1,100 Kda) chitosan solution significantly reduced microbial loads during a 6-month frozen storage (-20 degrees C) compared to uncoated alligator meats. The E. Coli count was not detectable for the chitosan-coated alligator meats during 2-6 months of frozen storage. The uncoated alligator meats had significantly higher TBA (lipid oxidation) values after 6 months of frozen storage. This indicated that chitosan was an effective antimicrobial and antioxidant agent for alligator meat during frozen storage. <LI>A macular optical densitometer for assessment of macular pigment density was ordered and delivered. Adults (18-30 years of age, n=12) will be recruited and asked to respond to a fish consumption questionnaire and to submit to the assessment of macular pigment density. Other subjects who consume fish 2 or more times per week (n=10) versus those who consume fish no more than once per month (n=10) will be measured for macular pigment density. </ol>