CRAWFISH PROCESSOR PREFERENCES FOR THE ADOPTION OF A POTENTIAL CRAWFISH PEELING MACHINE: A CONJOINT ANALYSIS

Louisiana crawfish processors' preferences for hypothetical crawfish peeling machines are evaluated using conjoint analysis. Of 5 attributes considered, deveining was the most important attribute. Retention of the hepatopancreas (fat), whether individual handling of crawfish was required, and retention of the backstrap were of roughly equal importance. Whether the machine was owned or leased was the least important attribute. The most preferred machine deveined, retained the hepatopancreas, did not require individual handling of crawfish, retained the backstrap, and was owned, though the ownership variable was not significant at the 0.05 level.     

A DEMAND ANALYSIS FOR CRUSTACEANS AT THE U.S. RETAIL STORE LEVEL

This study used a LA/AIDS model to estimate demand system for crustacean species, shrimp, crab, crawfish and lobster at the U.S. retail store level. Shrimp demand is price elastic; crab, crawfish and lobster are price inelastic. Shrimp price significantly affects market shares of crustacean products. Shrimp has more substitutes than other crustaceans, and lobster has less substitutes than others. The demand for crab and lobster grow faster than the demand for shrimp and crawfish when expenditure increases. Promotion has positive effects on market shares and sales volume of own products and negative effects on cross-products. Shrimp price-reduction promotion strategies will be effective in term of raising shrimp sales value. Marketing programs that increase consumers’ marginal utility with an additional small increase in the selling price of crab, crawfish and lobster products will be feasible, and bring higher sale values.     

CHANGES IN CRAWFISH PRODUCTION COSTS AND CURRENT PRODUCTION PRACTICES USED

Louisiana State University Agricultural Center cost estimates for single-crop crawfish production costs are analyzed for the period, 1991–2010, to determine changes in the cost components of Louisiana crawfish production. Fuel costs have contributed the most and fixed expenses the least to increased production costs, with total expenses per acre increasing by an average of 3.8% per year if land is not included and by 3.6% per year if land is included. Crawfish prices have varied greatly over the period, ranging from $0.50/lb in 1993 to $1.75/lb in 2000. Production practices used by Louisiana crawfish producers are highly variable, creating challenges for estimating representative production cost estimates.     

DETERMINING THE IMPACT OF CRAWFISH IMPORTS ON U.S. DOMESTIC PRICES

The study identifies the linkage between imports and the domestic price of crawfish. The results show a simultaneous increase in imports and domestic prices of crawfish while showing a negative relationship between domestic landings and price. Each model shows that there is a seasonality effect on the domestic price of crawfish. The study also shows that increases in the domestic supplies of shrimp, tilapia, and clams generated increases in the domestic crawfish price, while increases in imported and domestic supplies of beef and imported supplies of pork decreased the domestic crawfish price.     

Double-Cropping Malaysian Prawns,Macrobrachium rosenbergii,and Red Swamp Crawfish,Procambarus clarkii

Prawns, "Macrobrachium rosenbergii," and crawfish, "Procambarus clarkii," were alternatively grown in ponds to determine if they were compatible and if total production could be increased. Brood crawfish were stocked into replicated ponds at rates of 0,60, 120 or 180 kg/ha on 18 April. Water was removed to encourage burrowing. Following this, rice was planted as forage. Post-larval prawns (0.02 g) were stocked 3 July in all ponds at 17,500/ha. Prawns in half the ponds were fed and those in the other ponds were not. Ponds were drained from 7 to 11 October. Prawn production ranged from 157 to 248 kg/ha; survival ranged from 69% to 88%, and average size ranged from 11 to 7 g. There was no significant difference (P > 0.05) between fed and non-fed treatments. The ponds were reflooded and crawfish were harvested by trapping from 15 January to 15 May. The average yield of crawfish ranged from 746 to 1,266 kg/ha. Stocking rate had no effect of crawfish yields (P > 0.25). Total yield, with prawns and crawfish combined, ranged from 1,037 to 1,237 kg/ha. Overall, prawns and crawfish were compatible in rotation. Prawns were a good size for soft shell production during months when crawfish are not available for soft shell production.     

Evaluation of rice (Oryza sativa), volunteer vegetation,and alligatorweed (Alternanthera phyloxeroides) in various combinations as crawfish (Procambarus clarkii) forages

Four treatments of naturally occurring plants and planted rice were evaluated as forages in experimental crawfish ponds. Their relationships to biomass production, dawn dissolved oxygen, unstable water levels, and crawfish production were determined.Total standing biomass of forage at fall flooding was significantly lower (P < 0.01) for alligatorweed plus volunteer vegetation ponds compared with all other forage regimes. Average dawn dissolved oxygen during the first 5 weeks after flooding varied between 1.7 mg/l and 4.7 mg/l in ponds containing alligatorweed, compared with 1.0 mg/l and 1.5 mg/l in ponds containing other vegetation. Crawfish yields in kg/ha for ponds with stable water levels were: rice plus alligatorweed, 2852; rice only, 2652; rice plus volunteer vegetation, 2117. These forage treatments appeared to sustain the crawfish population, and stunting of crawfish at unmarketable sizes was not observed.     

Assessing Potential for Aquaculture Development with a Geographic Information System

Comprehensive analyses of aquaculture potential are required for policy formulation and planning for aquaculture development. A computer-automated geographical information system (CIS) was assessed as a tool to analyze the complex spatial and attribute data sets needed to locate aquaculture potential. The state of Louisiana, USA, was the study area. Areas for the further development of catfish and crawfish culture and crawfish-rice and crawfish-grain sorghum double cropping were identified. The CIS showed that there were ample opportunities for the expansion of catfish farming on flatlands based on soil suitability and length of the growing season. Parishes in which crawfish are already raised occupy most of the best suited soils and include those with the longest growing seasons. The potential to further integrate crawfish with rice and with grain sorghum in double cropping systems was good. The results demonstrated that a GIS can be used to aid large-area aquacultural development planning.     

Pond culturing of crawfish in the Southern United States

Due to a significant increase in the farming of crawfish by pond culture methods in the southern United States this paper briefly summarises the current practice being developed there.

Crawfish are cultured in shallow, open ponds surrounded on all sides by levees. The water depth seldom exceeds 45–61 cm. Area may vary, but the most popular sizes range from 2 to 16 ha. A rotation scheme involving rice and crawfish is generally practised, with rice serving as food for the crawfish.

Good management techniques are required for maximum crawfish production. One essential element is circulation of water through the ponds to keep dissolved oxygen concentrations above 5 mg litre⁻¹. With good quality water and proper management a harvest of up to 2200 kg ha⁻¹ yr⁻¹ may be realised.     

Effects of Water Quality,Weather and Lunar Phase on Crawfish Catch1

The relationship between water quality, weather, lunar phase and daily changes in crawfish (Proearnbums clurkii) catch per unit effort (CPUE) was determined in five experimental crawfish ponds from March through May, 1984 and 1985. Air and water temperatures, solar radiation, dissolved oxygen, wind velocity, barometric pressure, precipitation and lunar phase were recorded daily during the harvesting phase of the study. Crawfish CPUE (g/trap/24 h) was significantly correlated with water temperature, dissolved oxygen, lunar phase, barometric pressure, wind velocity and the relative density of harvestable size crawfish. Most statistically significant environmental or climatological variables explained less than 20% total daily variation in crawfish CPUE. The nine environmental variables were reduced to four factors—temperature-harvestable crawfish, cold fronts, rain showers, and lunar phase—with principal-components analysis. Eighty-five percent of the variation in daily crawfish catch was attributed to water temperature and relative density of harvestable crawfish, and 7.1% was explained by lunar phase. Rain showers and cold fronts accounted for 4.8 and 2.5% of the daily variation in crawfish CPUE, respectively. Crawfish catch increased with an increase in water temperature and relative abundance of harvestable crawfish, and with short duration rain showers. Conversely, crawfish CPUE declined with the approach of full moon and with passage of cold fronts.     

The Effect of Five Stocking Densities on Growth and Yield of Red Swamp Crawfish Procambarus clarkii

A 34-day study was conducted to estimate the effect of stocking density on growth, biomass, and yield of harvestable animals in red swamp crawfish, Procambarus clarkii (Girard). Juvenile crawfish were stocked at l, 2, 4, 8, and 16 crawfish per m² into plastic-lined metal pools planted with rice ( Oryza sativa ) with three replicate pools at each density. Crawfish averaged 35 ± 1.5 mm (SE) total length at the time of stocking.
Growth in total length and weight was significantly affected by density ( P < 0.01), ranging from 91.5 mm and 20.7 g for crawfish stocked at 1 per m² to 62.5 mm and 6.3 g for crawfish stocked at 16 per m². The total crawfish biomass ranged from 20.7 g per m² for crawfish stocked at 1 per m² to 88.7 g per m² at 16 per m². The portion of that biomass made up of harvestable sized animals (>75 mm total length) ranged from 100% at 1 per m² to 0.7% at 16 per m². Gross revenues per ha were projected for crawfish yields at each stocking density with and without a graded product.     

Effects of Supplemental Feeding on Harvest of Red Swamp Crawfish,Procambarus clarkii,in Forage‐based Ponds

Procambarid crawfish aquaculture in the USA relies on an established forage‐based system for providing sustenance for growing crawfish. These systems may become inadequate at times for providing sufficient nourishment to support maximum growth of the population. Supplemental feeding is not routinely used because management recommendations for the cost‐effective use of supplemental feeds in ponds are not available. Because crawfish under confinement readily consume and grow well when fed single feedstuffs, such as rough rice seed and whole, raw soybeans, this study was initiated to investigate the use of these readily available low‐cost feedstuffs as supplemental feeds in aquaculture ponds. Earthen ponds (0.2 ha), constructed and managed to simulate commercial crawfish ponds, were used over three consecutive production seasons to evaluate the effects of supplemental feeding on yields and size of crawfish. Treatments for Seasons 1 and 2 consisted of (a) hull‐on rough rice seed, (b) whole raw soybean, (c) formulated 25% crude protein pellet, and (d) no supplementation and were replicated in four and three ponds for Seasons 1 and 2, respectively. Treatments for Season 3 consisted of (a) whole raw soybean and (b) no feed, with 10 replicated ponds each. Feeding frequency was established each year, and feeding rates were adjusted according to predetermined guidelines and monitoring of feeding trays. Crawfish harvesting was conducted by baited wire‐mesh traps and all harvested crawfish were subjected to a mechanical grader and sorted into three size classes. Results show that supplemental feeding, while trap‐harvesting operations are underway, can reduce yields and generate a negative economic benefit, perhaps as a result of residual feed within the pond rendering the baited trap less effective.     

Molting,Mortality, and the Effects of Density in a Soft-Shell Crawfish Culture System 1

The molting and mortality patterns at a crawfish density recommended for commercial-scale soft-shell crawfish culture systems showed that, over a 116 day period, 74% of the crawfish molted, 22% died, and 4% remained in the system at the end of the study. Approximately three weeks of adaption to the system were required before molting rates of the crawfish began to increase. By the sixth week, the number of malted crawfish per day exceeded the overall mean and remained at this level until 10 days before moltable crawfish were depleted. In a second study, three density levels (3.7,4.9, and 6.1 kg crawfish/m²) were tested for 60 days. The lowest density produced significantly fewer (P < 0.05) molted crawfish. Mortality was significantly greater (P < 0.05) at the highest density compared with the lowest density. The highest density (6.1 kg crawfish/m²) showed a higher molting rate than the lower densities, but it was not significantly different (P < 0.05) from the molting rate of 4.9 kg/m².     

USE OF A SEINE TO DETECT STUNTED CRAWFISH POPULATIONS IN PONDS,A PRELIMINARY REPORT1

A 4.5-m long bag seine was used to sample crawfish from six 0.04 ha experimental ponds. Length-frequency histograms were evaluated as a predictor of size structure and to detect stunted populations of crawfish. The findings demonstrated importance of determining size structure of crawfish in predicting stunting and harvest potential of a population. Distinct differences in size structure of crawfish populations were apparent by 6 and 12 weeks after flooding ponds. Crawfish populations, with over 45% of the individuals exceeding 75 mm total length after 12 weeks, produced 25 to 30% greater yields than populations in which less than 5% of the crawfish exceeded 75 mm at 12 weeks post-flooding.     

Characteristics of Rice Cultivars with Implications for Crawfish Double Cropping1

Twenty-five domestic rice (Oryza sativa L.) cultivars were evaluated in a simulated rice/crawfish double cropping system in southwest Louisiana during 1983 and 1984. Wide variation was observed among cultivars in parameters believed to be important for maximizing productivity in such a system. Mean maturity ranged from 99 (Labelle) to 118 days (Starbonnet), while height ranged from 76 (Bellemont) to 130 cm (Della, Nato). Significant differences in grain yield response were observed, with yields ranging from 4,101 (Bluebelle) to 6,665 kg/hectare (Newbonnet). Straw dry matter production varied greatly, from 3,831 (Bellemont) to 9,170 kg/hectare (Della), and was positively correlated with plant height (r = 0.64; P = 0.0001). Ratoon biomass production was negatively correlated with both grain yield (r = -0.39; P = 0.0001) and maturity group (r = -0.69; P = 0.0001). Plant senescence at grain maturity also varied greatly and appears to be a factor in post-harvest ratoon capability. Early or very early maturing cultivars with both proven grain production and good ratooning capability appear best suited. Cultivar selection should be based upon individual farm situations and currently employed agronomic practices.     

盱眙发展龙虾业的比较优势

盱眙县政府从2000年起开始举办龙虾节，使得盱眙龙虾在全国掀起了一场“红色风暴”，而且呈现愈演愈烈的态势，形成了盱眙龙虾的产业化发展。而盱眙龙虾产业的发展要得益于盱眙龙虾的比较优势，文章主要从气候、水域、饵料及区位优势方面分析了盱眙龙虾的比较优势。     

Pre-Flood Evaluation of Seven Grasses (Graminae L.) as Planted Forage for Crawfish1

Seven potential alternatives to rice (Oryza sativa) as planted forage for pond production of crawfish in southwest Louisiana were evaluated. Browntop (Panicum ramosum L.), Japanese [Echinochloa crusgulli var. frumentacea (Roxb.) Wight], proso (Panicum miliaceum L.), and pearl [Pennisetum typhoides (Burn.) Stapf & C.E. Hubb] millets were compared with volunteer weeds (primarily Cyperus spp.), grain sorghum [Sorghum bicolor (L) Moench] and a sorghum sudangrass hybrid [S. bicolor (L.) Moench]. Early maturation and rapid senescence and decomposition characterized all except the two sorghums and pearl millet. The sorghum sudangrass was superior in biomass production and exhibited slow senescence. Grain sorghum and pearl millet also exhibited characteristics which might be desirable for use in some crawfish production ponds.     

Molting and Mortality of Red Swamp and White River Crawfish Subjected to Eyestalk Ablation: A Preliminary Study for Commercial Soft-Shell Crawfish Production

Eyestalk ablation may reduce the cost of soft-shell crawfish production by reducing the molt interval. In this study, both immature and mature red swamp crawfish Procambarus clarkii and white river crawfish Procambarus zonangulus , formally Procambarus actus actus (Hobbs and Hobbs 1990), were ablated using a pair of modified pliers and placed in a recirculating system. Molting percentages, mortalities and mean molt intervals of the ablated crawfish were analyzed.
Eyestalk ablation resulted in dramatic reduction of molt intervals and mortalities comparable with the current commercial (non-ablation) soft-shell crawfish production systems. The mean molt intervals of the ablated red swamp crawfish ranged from 6.7 to 7.8 days for immature and 9.2 days for mature animals; whereas, the molt interval of ablated white river crawfish was 8.9 and 11.2 days for immature and mature animals, respectively. Mortalities obtained in this study ranged from 20 to 48% and 32 to 66% for immature and mature crawfish, respectively. During the experiments, molting percentages and mortalities were not consistent. Secondary treatments such as air clotting and cauterization did not alter mortality significantly.     

Mixed model estmation of genetic and environmental correlations in red swamp crawfish Procambarus clarkii (Girard)

Total length, total weight, carapace length, carapace width, abdomen width, abdomen depth, chela length, chela width, abdomen meat weight and dressout percentage were measured on 752 individual crawfish Procambarus clarkii (Girard) from 39 full-sib families nested within 15 half-sib families. A nested mixed model analysis of variance and covariance was performed on all traits to obtain Henderson's method III variance and covariance components, as well as best linear unbiased estimators of the fixed effects of sex and male state of maturity. Genetic and environmental correlations were derived from mixed model variance and covariance components. Positive sire-based genetic correlations suggest that genetic gains in growth and processing yields, the major components of value of harvestable P. clarkii, may be pursued simultaneously in future breeding programmes. Data suggest that easily obtained external measurements are sufficiently correlated with growth and processing traits to allow for identification of potentially superior broodstock. Female, mature male and immature male levels of fixed effects, as well as estimated heritabilities for individual growth, body size and processing traits, were consistent with previous studies, further reinforcing the validity of data developed to date for use in planning P. clarkii breeding programmes.     

Predicting Crawfish Molting with Machine Vision

The objective of this project was to develop a vision system that could predict when crawfish will molt. Different sections of the crawfish shell were examined to determine how the color changed as the time of molting approached. A strip on the tail section of the crawfish showed the greatest, most consistent color change. The average red/green × red/blue ratio decreased for every crawfish as the molting time approached. Using this ratio as a predictor, it was possible to predict the molting of a crawfish within 3 d with an accuracy greater than 80%. The limitation on accuracy was primarily the result of the large variations in natural shell color among the crawfish.     

Evaluation of Trap Density and Type for Harvesting Crawfish Procambarus spp. from Small Ponds

Harvested crawfish were stocked into 0.15-ha earthen ponds in March and May at rates of 114, 227, and 455 kg/ha to evaluate the effects of trap density, 27 and 54 traps/ha, on their recapture over 14 d following 3 d of acclimation. Two-funnel, stand-up pillow traps and three-funnel pyramid traps were compared. About 39% and 55% of stocked crawfish were recovered in March and May, respectively. There was considerable growth of those crawfish. Overall catch with both trap densities was equivalent in March but the higher trap density caught 1.3 times more crawfish in May. Pyramid traps caught 1.5–1.9 times more crawfish than pillow traps.