Improving Louisiana's Aquaculture Production and Food Industries

Non-Technical Summary: Louisiana supports one of the most diverse aquaculture industries in the nation. Numerous challenges require development of new technologies to ensure that the state's aquaculture industries remain viable and profitable. Crawfish production, the leading aquacultural enterprise, relies on baited, wire-mesh traps to harvest the crop and harvesting comprises 50-60% of the annual production costs. Numerous issues related to bait-crawfish-trap interactions need to be further researched for the development of more cost-effective trapping strategies. In addition, seasonality of crawfish harvest, which occurs primarily in winter-spring, is a major constraint to expanding the market. Availability of crawfish for peeling and specialty markets is needed in summer and fall. Therefore, determination of the potential of alternative species, such as the shrimp crawfish (O. lancifer), to commercial culture conditions is needed. Louisiana is the largest producer of farm-raised alligators in the nation and little research on the nutritional needs of alligators has been conducted. Baseline research on how alligators process common feedstuffs will begin an initiative to develop nutritionally sound diets at low cost. The development of an aquaculture industry centered on the culture of marine baitfish, such as the Gulf Killifish (F. grandis), represents a potential new economic market within Louisiana. Therefore, the application of air incubation as a hatchery and larval rearing technique for the Gulf Killifish will be investigated with an ultimate goal of providing a consistent source of this species to Louisiana anglers. Vibrio vulnificus is a naturally occurring estuarine pathogen frequently transmitted via raw oysters and it is important to reduce the prevalence rate of its infection to humans. Chitosan is a non-toxic biopolymer with antimicrobial and gel-forming properties produced from crawfish waste, which may have the ability to maintain the sensory quality of raw oysters while enhancing their safety and shelf-life. In addition, the need to determine the most cost effective freezing method for aquacultural food products, a major expense in the operation of a processing plant and a growing segment of the market, is greatly needed. So, cryogenic freezing methods will be compared to blast-freezing in relation to yield, quality, and shelf-life of various aquacultural food products. Finally, Photobacterium damsela subspecies piscicida is a serious and important disease of marine fish worldwide and has greatly affected several hybrid striped bass farms on the Gulf Coast. Using molecular biology procedures, important virulence factors of this disease will be determined to provide insight for planning future research concerning pathogensis, control, and prevention. <P> Approach: This proposal contains seven component projects, each with the goal of enhancing Louisiana's aquaculture industry. 1) Experiments in monoculture and rice/crawfish rotation ponds with crawfish marked with a permanent, water insoluble marker will determine the capture efficiency of different commercial crawfish traps, quantify the catch efficiency of traps in various crawfish populations, increase the efficacy of baited traps with decreased bait use, identify alternative baits that may be effective attractants in cold/cool waters and evaluate potential bait-free trapping alternatives. 2) Juvenile shrimp crawfish will be stocked into pools with soil and aeration at densities that will allow comparison of previous research with the red swamp crawfish. Experiments will be conducted on stocking density, vegetation and planting date, and benefits, if any, from supplemental feeding. 3) Twenty young-of-year American alligator will be obtained from a single clutch of eggs and stocked in tanks (one per tank) in a wet laboratory. Each feed ingredient, mixed with chromic oxide (indicator) and force-fed in slurry form, will be assigned to four tanks using a completely randomized design. Diets and fecal samples will be subjected to proximate analysis to determine levels of crude protein, lipid, fiber, ash and carbohydrate. 4) To identify the optimum temperatures and salinity for incubation protocols, batches of newly fertilized Gulf Killifish eggs (about 500) will be incubated in water and air at temperatures of 19, 22, 25, 28, and 31 degrees C with optimum substrate. Trials at varying salinities (0, 5, 10, 15 ppt) will determine the role of salinity on developmental rate and percent hatch. These experiments will demonstrate the relationship between survival and the degree of development and egg-yolk utilized during the delayed hatch phase of air incubated eggs. 5) An available automated sequence of the P. damselae genome will be used and a large insert (10-20 kb) DNA library constructed in the linear cloning vector pJAZZ- KA for manual paired end sequencing. This will allow for gap closure and ordering of contigs. Final closure will rely on PCR and primer walking. Annotation will utilize services at the J. Craig Ventor Institute, Rockville, MD. 6) Freshly harvested live oysters will be shucked and either (1) soaked in ozonated water and then chitosan solution or (2) soaked in chitosan solution only. They will then be placed in containers and stored at 4 degrees C for up to 21 days. Samples will be drawn every 3 days for V. parahaemolyticus and V. vulnificus counts (CFU/g) and subjected to evaluation of sensory quality. 7) A cabinet type cryogenic freezer capable of utilizing both liquid carbon dioxide and liquid nitrogen will be used for cryogenic-freezing, while a blast freezer will be used for mechanical freezing. Aquaculture food products will be separately placed in the cryogenic freezer or blast freezer and frozen to an internal temperature of -20 degrees C. Initial weight, product temperature, moisture, protein, lipids, and ash will be analyzed. Freezing-rate, moisture-loss, and weight-loss of the seafood for each freezing method will be determined.