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.     

Diversification of Crawfish Management Schedule1

Six 0.02 ha ponds were used to evaluate crawfish production and standing crop biomass of rice forage in ponds managed on a standard (control) and delayed (experimental) schedule over a two year production cycle. Delayed schedule followed the same sequence of events except the management activities were delayed approximately one month. Control and experimental ponds had statistically similar amounts of forage. No statistical difference was detected in crawfish production between the management schedules or between production years; however, analysis revealed a significant treatment × year interaction. Overall average crawfish production was 986 kg/ha. Variation in crawfish production is explained within the context of annual temperature variations and differences in population density.     

Preliminary Evaluation of Production Systems and Forages for Culture of Orconectes virilis, the Northern or Fantail Crayfish

Culture potential of Orconectes virilis , the northern or fantail crayfish, was evaluated in deep ponds and simulated shallow ponds during the summer and fall. Adult crayfish were stocked in the deep ponds in October and known numbers of juvenile crayfish were stocked in the shallow ponds in May. Triplicate groups of crayfish in each system were either not fed (negative control) or fed corn silage or wheat straw. Production in either system was not significantly different between treatments, but production in the shallow tanks (790 kg/ha) was almost double that observed in the deep ponds (401 kg/ha) and may have been due to different stocking strategies. Juvenile crayfish were generally of minimal marketable size at the end of one growing season. The shallow tanks were restocked in October and drained in March to evaluate overwinter survival in this type of system. Survival averaged 78.9% for both males and females, and most (97.1%) age 1 females were carrying eggs.     

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.     

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.     

克氏原螯虾的生态养殖⑤ 上海海洋大学克氏原螯虾生态养殖课题组协办 克氏原螯虾高效生态养殖模式

近年来,克氏原螯虾的养殖发展迅猛,已在全国各地形成各具特色的高效生态养殖模式,前面介绍的池塘生态养殖和稻田生态养殖只是众多模式中的一部分,下面介绍其它几种养殖模式,供广大养殖户借鉴.     

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.     

Effectiveness of Commercially Formulated and Fish Baits in Trapping Cambarid Crawfish1

In the USA, cambarid crawfishes are harvested commercially with traps baited with fishes, formulated baits, or a combination of the two. Commercially formulated baits and fish baits, done and in combination, were evaluated to assess their relative effectiveness M attractants for crawfish. Traps baited with a combination of fish and formulated bait generally captured the most crawfish. Traps baited with common carp, the most effective natural bait, captured more crawfish than traps baited with skipjack herring, gizzard shad or channel catfish heads. Crawfish harvest from traps baited with several types of commercially formulated baits was equal to that obtained with traps baited with either gizzard shad or skipjack herring. Population density of crawfish and the availability of natural forage did not appear to influence relative effectiveness of either formulated baits or fish baits.     

Growth of Crawfish Procambarus clarkii as a Function of Density and Food Resources

This study utilized enclosures (cylindrical, 5-mm wire mesh, O.5 m² bottom surface area) placed over rice-forage substrates in experimental crawfish ponds to contain crawfish under typical pond culture conditions. Juvenile Procambarus clarkii were stocked at six densities (2, 4, 6, 10, 14, and 18 crawfish/m²) for 12-wk growth trials in October and again in February. Crawfish relied solely on the detrital food system for their nutritional needs. Supplemental feed was supplied to crawfish in additional enclosures at two of the test densities (2 and 10 crawfish/m²). The commercially formulated feed (25% crude protein) was fed (2.02 g dry feed/m²) 3 d/wk (Monday, Wednesday, Friday). All treatments were replicated with six enclosures. Crawfish growth was inversely correlated to culture density. Mean final weights for crawfish feeding from the detrital-system only were 15.3, 13.8, 11.2, 7.9, 7.2, and 5.8 g for crawfish densities of 2, 4, 6, 8, 10, 14, and 18/m², respectively. Mean final weights for crawfish receiving supplemental feed were 20.7 and 12.4 g for densities of 2 and 10 crawfish/m². When compared with density as a factor influencing growth, feed influenced growth less than density abatement. Supplemental feeding improved crawfish growth in detrital systems an average of 46%, while decreasing initial density improved growth an average of 80.5%.     

Cage Culture of Hybrid Striped Bass in Indiana and Evaluation of Diets Containing Three Levels of Dietary Protein1

Culture of hybrid striped bass Morone saxatilis × M. chrysops has been increasing in selected regions of the United States. Because of their thermal tolerance, hybrids may have potential as a new commercial aquaculture species in the Midwest. In these studies, hybrid striped bass were reared in cages located in southern, central and northern Indiana and offered one of three practical diets. Diets contained either 32, 36 or 40% crude protein. Additionally, a preliminary 8 wk laboratory experiment was conducted in which fish were offered the same diets. All diets were formulated to meet the established dietary lysine requirement; optimal levels of other essential amino acids in the diet were predicted by the whole-body essential amino acid profile of hybrid striped bass. In the laboratory experiment, weight gain of fish fed 36% crude protein was significantly higher than those fed either other level of dietary protein. After 205 days, final average weight gains of fish in the field experiment were not significantly different and ranged from 233 to 426 g with an overall average daily gain of 1.6 g/fish/d. Overall survival was 89.1%. Dress-out percentages were 81.2, 69.8, and 34.9% for eviscerated, eviscerated and headed, and fillets, respectively. Those values were not significantly different among dietary treatments or sites. Lipid content of fillets from fish fed 32% dietary crude protein was significantly higher than in fish fed 36 or 40% crude protein.     

Substitution of Soybean Protein for Fish Protein in Formulated Diets for Red Swamp Crawfish Procambarus clarkii1

A 10 week laboratory growth trial was conducted with red swamp crawfish Procambarus clarkii to determine the amount of soybean protein that could be substituted for fish protein in formulated crawfish diets without reducing growth. Crawfish received 32% crude protein, isocaloric diets in which protein was supplied by soybean (soy) meal, menhaden fish meal or an isonitrogenous mixture of soybean and fish meal calculated to provide graded levels of each protein source. Dietary protein was provided as: 1) 100% soy protein; 2) 75% soy protein: 25% fish protein; 3) 50% soy protein: 50% fish protein; 4) 25% soy protein: 75% fish protein; and 5) 100% fish protein. Crawfish fed soy protein: fish protein (SP:FP) mixtures or fish protein alone exhibited better (P < 0.05) weight gain than crawfish fed a diet containing soy protein as the only protein source. Diets containing 25% soy protein: 75% fish protein (1:3 ratio) and 50% soy protein: 50% fish protein (1:1 ratio) produced greater (P < 0.05) weight gains than a diet in which fish protein was the sole protein source. Survival, feed efficiency ratio, maturation rate, net protein and energy retention, and body composition of crawfish did not differ (P > 0.05) among diets with SP:FP ratios of 1:3, 1:1 and 3:1. However, maximum (P < 0.05) weight gain occurred in crawfish fed the 1:3 SP:FP ratio. Although crawfish fed SP:FP ratios of 1:1 and 3:1 had lower weight gains in the laboratory than crawfish fed a 1:3 SP:FP ratio, SP:FP ratios of 1:1 and 3:1 might be adequate for supplemental diets fed to pond-reared crawfish that have access to natural sources of food.     

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.     

Feasibility Study for Alternative Culture Species in Taiwan—Penaeus penicillatus

Penueus monodon has become almost synonymous with aquaculture in Taiwan, indicating the level of commercial success it has attained over the past two decades. However, other species are being considered for future culture to diversify an industry overly dependent on one product, as well as to provide the market with an alternative commodity. This paper explores the feasibility of P. penicillatus as an alternative culture species in Taiwan.
P. penicillatus has seven merits that make it ideal for aquaculture: 1) P. penicillatus is comparatively resistant to low temperature. 2) It is a medium sized "white prawn" and is attractive to the consumer. 3) The migration behavior shows good possibilities for culture in sea water. 4) Wild spawners are abundant and natural, and induced spawning in captivity is relatively easy. 5) Larvae spontaneously spawned in captivity show good survival, existing on the natural food present in the pond. 6) It has a low protein requirement and has good growth in the early stages even at high stocking densities of 100–120 prawns/m². 7) P. penicillutus grows to a comparatively uniform size. This paper also discusses some difficulties in the culture of this prawn.     

Intensive Culture Potential of Penaeus vannamei

Tank and pond rearing studies were conducted to assess the potential for intensive culture of Penaeus vannamei in South Carolina. Postlarvae were stocked in intensive nursery tanks at 500/ m². Growth and survival were compared for shrimp reared in control fiberglass tanks and in tanks with artificial substrates (fiberglass screen). Addition of substrate improved survival (82% versus 58%), but not growth. Juvenile shrimp (mean weight, 1.3 g) from the nursery trial were stocked into 6 m diameter tanks at densities of 10, 20 and 40/m². Growth rate was inversely related to stocking density, with mean sizes of 33.9, 32.5, and 26.7 g attained at the low, medium, and high densities respectively after 168 days. At harvest, standing crop biomass averaged 225.6, 442.0, and 685.4 g/m² for the three densities. To further test the intensive culture potential, two 0.1 ha ponds were stocked with hatchery-reared postlarvae at densities of approximately 40 and 45/m². The ponds were managed intensively using paddlewheel aerators and water exchange averaging 16–17%/day. The ponds were harvested after 138 and 169 days and yielded 6,010 kg/ha of 16.7 g (mean weight) shrimp and 7,503 kg/ha of 17.9 g shrimp, respectively. Average production was 6,757 kg/ha with a food conversion of 2.51. These data suggest good potential for intensive pond culture of P. vannamei in South Carolina and other areas of the continental United States.     

提高池塘蓄水养蛏产量的三项关键技术

池塘蓄水养殖缢蛏具有生长快,养殖周期短,产量高,单位成本低等优点,是一种高产、高效、优质的养殖模式,严格掌握并有效地控制水质、饵料、底质三要素,是提高蓄水养蛏产量的关键。     

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.     

生物技术对鱼类养殖的潜在影响

随着科学技术的发展,除了传统的生物技术之外,分子技术的应用已经为提高世界水产养殖品种产量开辟了另一条途径.基因组信息库的增长,极大地提高了科技工作者对确认一些表现型基因的能力.转基因技术和目前尖端的技术：诸如DNA芯片技术、高分辨力的二维凝胶技术和高灵敏度的质谱仪等技术的发展联系起来,向水产养殖工作者展现出了一片美好的前景：包括生长率和经济效益的增加、抗病能力和抗冻能力的提高、养殖品种种质的改善以及通过改变它们的基因组成而创造出新的不同的品种.讨论了与功能基因组领域相关的技术以及它们在水产养殖领域中的应用.     

Evaluation of Naturally-Occurring Organisms as Food for Juvenile Crayfish Procambarus clarkii1

Nutritionally important food items for crayfish have been difficult to identify and little information exists for third instar (first-feeding) crayfish. In this study, three major groups of potentially-important foods were fed to communally-reared third instar crayfish (Procambarus clarkii) and weight gain and survival were measured over a 30 day period. Mean weight gain (% increase) of crayfish fed the zooplankton Daphnia magna alone or in combination with other food items, ranged 2, 277–3, 239%, while mean weight gain of crayfish fed unidentified aquatic bacteria, the aquatic macrophyte Myriophyllum spicatus, combinations of bacteria and plant, or a negative control ranged 254–767%. No significant interaction of food items was detected. Bacteria appear to be a utilizable nutritional source for juvenile crayfish, but, using the methods employed in this study, do not support maximum rates of weight gain. Thus, pond management strategies that maximize zooplankton populations at the time of crayfish hatching might be beneficial.     

Comparison of Three Culture Methods for the Intensive Culture of Northern Quahog Seed, Mercenaria mercenaria

A number of approaches have been utilized for growing bivalve hatchery seed (1 mm) to a size suitable for field planting (< 8 mm) but few have been directly compared. This study evaluated the growth and survival of northern quahog seed in three different culture systems and two different stocking densities. The three systems were: 1) a stacked-tray unit with downward water flow; 2) traditional upweller culture units with water flowing upward without seed bed expansion; and 3) upweller culture units with water flowing upward at fluidization velocities to provide seed bed expansion. The two stocking densities were 1.0 and 3.0 g whole wet weight clam/cm² respectively. During each trial period the seed clams were fed a 1% daily ration (% dry weight algae per wet weight clam per day) of the cultured diatom Chaetoceros muelleri . After 14 d of culture at the 1.0 g whole wet weight/cm² stocking density, seed clams (4.4 ± 0.6 mm initial shell length) under fluidized-flow condition exhibited better growth (0.54/d), and a greater final shell length (5.9 ± 1.0 mm). At the high density stocking conditions, after 28 d of culture, seed clams (4.2 ± 0.6 mm initial shell length) in the fluidized-flow culture conditions again exhibited better growth rate (0.031/d) and a greater final shell length (6.0 ± 1.0 mm). The preliminary evaluation of fluidized-flow for seed clam culture in land-based nurseries indicates its potential as a suitable alternative to raceway, downwelling, or traditional forced-flow culture methods.