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.     

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.     

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.     

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.     

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.     

Effects of Added Substrate on Production of Red Swamp Crawfish, Procambarus clarkii, in Earthen Ponds without Planted Forage

The effects of addition of substrate consisting of plastic mesh fencing to experimental earthen ponds were evaluated for the culture of the red swamp crawfish, Procambarus clarkii, without planted forage. Mean daily yield (kg/ha/d), number of crawfish harvested (number/ha/d), and mean individual harvest weight were compared for ponds with and without substrate during a 2‐yr period. The surface area of added substrate was equivalent to 50% of the bottom surface area of the pond. Mean daily yield in the ponds containing substrate, based on a comparison with that of the previous year, increased by 80.2% and was principally attributed to a 66.7% increase in the number of crawfish harvested. Comparative values for the ponds without substrate were ?13.1 and ?11.7%. For the second year, the treatment‐dependent response was consistent. Mean daily yield for the substrate ponds increased by 48.8% compared to 15.0% for the ponds lacking substrate. The primary benefit of the substrate appears to be provision of refuge and three‐dimensional distribution of crawfish in the pond, thereby reducing the incidence of cannibalism and increasing the total number of crawfish harvested per hectare per day. The benefit of the substrate in a commercial production setting must be weighed against its cost and longevity as well as the conditions of the particular management scenario into which it may be incorporated.     

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.     

Effects of Population Density and Feeding Rate on Growth and Feed Consumption of Red Swamp Crawfish Procambarns clarkii

Wire-mesh enclosures were used in production ponds to conduct growth trials in which population density and feeding rate were evaluated in a 2 × 2 factorial arrangement for their effects on crawfish growth. Juvenile Procambarus clarkii of uniform size (0.5 g) were stocked at 2 or 20 animals/m² in experiment 1 and weighed biweekly for 12 wk. Rice forage served as the detrital base, and supplemental feed (25% crude protein) was provided at either a low (26–52 kg/ha per week) or high (104–418 kg/ha per week) rate. In experiment 2, mixed sizes of crawfish were stocked at 10/m² or 20/m² and fed the formulated feed at either 52 or 312 kg/ha per week. Feed consumption was estimated for each treatment combination. Only population density significantly affected crawfish growth. Mean weight gain and final weights were inversely proportional to density but only when total crawfish biomass exceeded 1,235 kg/ha. Growth was not significantly influenced by feeding rate, but the high feeding rate resulted in a significantly greater ratio of hepatopancreas weight to body weight and tended to decrease hepatopancreas moisture levels, indicating improved condition. Population density, feeding rate, and their interaction had significant effects on estimated feed consumption. From the simple linear regression of mean feed consumption on crawfish standing crop, it was estimated that crawfish consume about 0.1 kg of dry feed per ha per week per kg of crawfish biomass on a 5 d per week feeding schedule at mean water temperatures, ranging from 14 to 30 C.     

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.     

Engineering considerations for water circulation in crawfish ponds with paddlewheel aerators

Engineering considerations for paddlewheel aeration in vegetated shallow water ponds for the production of procambarid crawfish is necessary to ensure cost-effective application. Three experimental ponds (approximately 2 ha each) were planted with rice in August as forage for the resident pond population of red swamp crawfish, Procambarus clarkii, and flooded in October. Two 2.2 kW (3 hp), single-phase electric motor (110 V_ac) paddlewheel aerators were placed in each pond. The aerator rotors were 160-cm long and 95-cm in diameter. The aerator rotor had 36 paddles with half the paddles 27.3-cm long and half 34.9-cm long. Rotor speed was set at 83 rpm and operated at three paddle submergence settings: 7.6, 12.7, and 17.8 cm below the water surface. Over a 20-week period between November and April, channel velocity, head difference, and aerator amperage was measured for both one and two aerators in operation in each pond. Results indicated that circulation of oxygenated water from the aerators can be accomplished as efficiently with a single aerator set at a lower paddle depth (7.6-cm) compared to operating two aerators set at a greater paddle depth (12.7 or 17.8-cm). However, based on the apparent efficiency of the aerators and the calculated channel roughness coefficients values obtained from the channel velocities, paddlewheel aerators are an inefficient option for circulating the pond water especially when rice foliage dominants the total vegetative biomass of the pond.     

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.     

Using residual water from a marine shrimp farming BFT system. Part II: Artemia franciscana biomass production fed microalgae grown in reused BFT water

The residual water from intensive aquaculture production systems can be utilized in integrated multitrophic cultivations. In this work, Artemia franciscana received daily feedings of 10 mg L^?1 of Tetraselmis chuii, Nannochloropsis oculata and Chaetoceros muelleri, which were grown using residual water from an intensive biofloc Litopenaeus vannamei cultivation system. The goal of this study was to verify which species provide the best zootechnical performance and best crustacean biomass production efficiency. After 12 days of cultivation, A. franciscana wet biomass was 815.64 ± 18.74, 650.81 ± 83.98 and 40.76 ± 4.08 mg L^?1 with C. muelleri, T. chuii and N. oculata (P < 0.05), with significant differences in dried biomass as well. As for the microalgae cultivation in the alternative culture medium, T. chuii had higher dry biomass gain, requiring less culture volume to achieve 10 mg L^?1 and become ready to feed Artemia. Thus, T. chuii was the most efficient in Artemia biomass production with 0.83 L compared to 1.54 L g art^?1 in C. muelleri. C. muelleri is recommended for feeding A. franciscana for biomass production purposes. However, due to its better efficiency, T. chuii can be selected to be part of a multitrophic system.     

Replacement of fishmeal by vegetable meal mix in the diets of Litopenaeus vannamei reared in low‐salinity biofloc system: effect on digestive enzymatic activity

Biofloc (consortium of diverse microorganisms associated to suspending substrates) was developed from waste of shrimp Litopenaeus vannamei postlarvae culture under low salinity (5 g L^?1) to provide an additional nutritious biomass and reduce fishmeal inclusion in feeds in a 28‐day indoor shrimp nursery trial conducted in 15 experimental containers (250 L stocked at 600 org m^?3). Four experimental diets (isoproteic and isocaloric) containing different percentage of fishmeal: 0%, 10%, 20% and 30% substituted by vegetable meal mix (corn, sorghum and wheat) were formulated and elaborated. A control treatment consisted of a commercial feed. The main water quality parameters were monitored, and no significant differences were found among treatments. The growth and survival were similar among treatments. In general, digestive enzymatic activities showed differences being greater in the biofloc system compared with clear water. It was concluded that low‐salinity shrimp nursery could be successfully developed with minimum inclusion of fishmeal in feeds, without significant effect on production response. The adjustment of C : N ratio allowed the increase of microbial biomass in the bioflocs, which contributed to maintain good water quality, provide live food and enhance digestive enzymatic activity of cultured organisms.     

Effect of feeding different grain sources on the growth performance and body composition of tilapia, Oreochromis niloticus (L.)

Growth performance and body composition of tilapia Oreochromis niloticus (L.), fed isonitrogenous and isoenergetic diets containing different grain sources (maize, wheat, barley, sorghum and rice) at a level of 25% were studied for a period of 62 days. Fish fed a diet containing sorghum showed the maximum weight grain, highest specific growth rate (SGR, 2.23), the best feed conversion (FCR, 1.07) and protein efficiency ratio (PER, 2.42) in comparison with all other diets. The diets containing maize, wheat and rice did not show any significant (P < 0.05) differences between each other. The barley diet showed the poorest values (SGR, 2.05; FCR. 1.34; PER, 1.98: and NPR, 30.65) in comparison with others. Although the diet containing sorghum showed the best net protein retention (NPR, 36.21) values, the results did not differ (P > 0.05) among maize, wheat and sorghum diets. The sorghum diet produced fish with lower moisture but higher body fat contents as compared to others. The fish fed diets containing maize, wheat, barley and rice did not show any significant difference (P > 0.05) in their body moisture and fat contents. The source of grain in the diet did not affect the crude protein and ash contents of fish (P > 0.05). It is suggested that cereal grains at the 25% level can efficiently be utilized in tilapia diets, sorghum being the best.     

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.     

A changed post‐flood management strategy enables the culture‐based fishery of the Liangzi Lake,Yangtze River Basin,China, to remain economically and environmentally viable

The culture‐based fishery of Liangzi Lake, Yangtze River Basin, established in 1992, yielded 2,652 t/year (±167) between 2005 and 2015, dominated by stocked carps [Hypophthalmichthys molitrix (Val.) and Hypophthalmichthys nobilis (Richardson)] and mitten crab Eriocheir sinensis (Milne Edwards), accounting for 53% and 23% of the production and 20% and 52% in value, respectively. The lake had a macrophyte cover dominated by Vallisneria natans (Lour.) Hara with a cumulative biomass of 10,647 g/m² that disappeared after a major flood in 2010 and changed its ecology. Management changes in stocking strategies introduced in the post‐flood period enabled the culture‐based fishery to maintain viability and sustainability to combat the major ecological change in the lake. The stocked species contributed significantly to nutrient removal of 24.71 ± 5.12 t/yr and 6.29 ± 0.87 t/yr of total nitrogen and total phosphorus, respectively.     

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.     

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.     

Mud crab pen culture: replacement of fish feed requirement and impacts on mangrove community structure

Brackishwater pond culture has been a major factor in mangrove loss in Southeast Asia, hence, the need to develop environment‐friendly technologies such as mud crab Scylla (Portunidae) culture in mangrove pens exists. This study evaluated the effects of mud crab netpen systems in central Philippines on mangrove macroflora, and the replacement of dietary fish with low‐cost pellets. Wild or hatchery‐sourced Scylla olivacea and Scylla serrata were stocked at 0.5–0.8 m⁻² in 167–200 m² nylon netpens (2.3 cm stretched mesh) in Avicennia‐dominated mangrove habitats. The feeding treatments were: (A) Zarraga: (1) no feeding (natural productivity), (2) no feeding for 1 month+supplementary feeding, (3) fish biomass and (4) low‐cost pellets, and (B) Batan: (1) fish biomass and (2) pellets+fish biomass. Feeds were given ad libitum twice daily. Growth and survival rates of S. olivacea in Zarraga pens were not significantly different among treatments, although crabs fed fish biomass had the highest survival, body weight and production. Similarly, growth and survival of S. serrata were not significantly different between the Batan treatments. Economic analysis of the latter gave a 38.5% return on investment (ROI) and 2.6 years payback period (PP) for pellets+fish biomass treatment compared with 27.5% ROI and 3.6 years PP for fish alone. Sensitivity analysis showed an improved economic performance of the pellets+fish biomass treatment by increasing the survival rate. Evaluation of mangrove community structure showed that crab culture reduced species diversity, numbers and biomass of seedlings and saplings, but not of mangrove trees. Therefore, mud crab pen culture is recommended for mangrove sites with mature trees, but not seedlings and saplings, and low‐cost pellets can reduce dependence on fish biomass.     

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.