Production of Oreochromis niloticus (L.) and ecosystem dynamics in manured ponds of three depths

Abstract. During three 5-month experiments in Thailand, earthen ponds of approximately 370m2 surface area were stocked with male Nile tilapia, Oreochromis niloticus (L.), fingerlings of 4–12g weight at densities of 0·5 to l·6fish/m². Stocking and fertilization (with chicken manure, urea and TSP) in triplicated depth treatments of 0·6,1·0 and 1·5m were proportional to pond volume in two experiments (wet and dry seasons) and to pond area in the other (dry season).
Depth showed no direct effect on fish yields of 0·9–6·3t/ha/year, on survival rates of 66 to 98%, nor on final individual weights of 96–313 g/fish. Greater yields were obtained from deeper ponds when they received proportionally greater stocking and fertilizer inputs. Inputs per unit area were the most important factor accounting for yield variation.
Temperature, dissolved N and P, and suspended solids showed little or no relation to depth treatments. Time-averaged chlorophyll concentrations and photosynthetic production of dissolved oxygen were greater in treatments receiving greater inputs of nitrogen per unit pond volume.
Deeper ponds produced the greatest areal yields of fish, when fertilized in proportion to their volumes. Shallow ponds produced fish and dissolved oxygen at least as efficiently per unit input as did deep ponds, which is consistent with models of photosynthesis-depth relations.     

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.     

Effect of Water Exchange Rate on Production, Water Quality, Effluent Characteristics and Nitrogen Budgets of Intensive Shrimp Ponds

Water exchange is routinely used in shrimp culture. However, there are few, if any, systematic investigations upon which to base exchange rates. Furthermore, environmental impacts of pond effluent threaten to hinder further development of shrimp farming in the U.S. The present study was designed to determine effects of normal (25.0%/d), reduced (2.5%/d) and no (0%/d) water exchange on water quality and production in intensive shrimp ponds stocked with Penaeus setiferus at 44 postlarvae/m². Additional no-exchange ponds were stocked with 22 and 66 postlarvae/m² to explore density effects. Water exchange rates and stocking density influenced most water quality parameters measured, including dissolved oxygen, pH, ammonia, nitrite, nitrate, Kjeldahl nitrogen, soluble orthophosphate, biochemical oxygen demand, phytoplankton and salinity. Reduced-exchange and no-exchange treatments resulted in reduced potential for environmental impact. Mass balance of nitrogen for the system indicates that 13–46% of nitrogen input via feed is lost through nitrification and atmospheric diffusion. Growth and survival were excellent in ponds with normal exchange, reduced exchange, and a combination of low density with no water exchange. A combination of higher stocking density and no water exchange resulted in mass mortalities. Mortalities could not be attributed to a toxic effect of any one water quality parameter. Production was 6,400 kg/ha/crop with moderate stocking density (44/m²) and reduced (2.5%/d) water exchange and 3,200 kg/ha/crop with lower stocking density (22/m²) and no water exchange. Results indicate that typical water exchange rates used in intensive shrimp farms may be drastically reduced resulting in a cost savings to farms and reduced potential for environmental impact from effluent.     

Growth and Survival of the Australian Red Claw Crayfish Cherax quadricarinatus at Three Densities in Earthen Ponds

Australian red claw crayfish Cherax quadricarinatus were cultured in nine 0.02-ha earthen ponds at densities of l/m², 3/m² and 5/m² for 158 d. Average weight at stocking was 3.2 g. All ponds were provided with a combination of hay and corn silage at a rate of 500 kg/ha per month and a commercial crayfish ration fed at 5%, decreasing to 2% of estimated biomass/d during the growing season. Overall survival rate was 72%, and did not differ among treatments. Final yields and average weights varied significantly with stocking density. Red claw averaged 67 g with an average pond yield of 475 kg/ha at l/m². At 3/m² and 5/m², red claw averaged 48 g and 38 g, respectively, and yielded 1,020 kg/ha and 1,422 kg/ha, respectively.     

The role of chicken manure in the production of Nile tilapia, Oreochromis niloticus (L.)

Abstract. Two grow-out experiments were conducted to evaluate the functional role of chicken manure for Nile tilapia, Oreochromis niloticus (L.). production in central Thailand. Experiment 1 examined the relationship between chicken manure input and net fish yield (NFY). Experiment 2 determined the value of chicken manure in providing tilapia particulate organic carbon, and/or dissolved inorganic carbon (DIC) for stimulating algal productivity. In both experiments supplemental urea and triple superphosphate (TSP) gave all treatments total nitrogen (N) and phosphorus (P) inputs of 28·0kg/ha/week and 7·0kg/ha/week, respectively.
Addition of chicken manure to inorganic fertilization did not enhance production of Nile tilapia. NFY in experiment 1 increased with decreasing manure loading, which corresponded to increasing TSP input. Regression analysis suggested that chicken manure-P was about 10% effective as TSP-P at increasing NFY. NFY was linearly correlated to net primary productivity (r²= 0·62, P < 0·001), which was linearly correlated to total alkalinity (r²= 0·77. P < 0·001).Treatment differences in alkalinity, community respiration or dissolved oxygen concentrations at dawn were not related to manure input. Simple economic comparisons discourage the purchase of chicken manure as a source of soluble N and P for increasing algal productivity in Thailand.     

Production of Nile Tilapia Oreochromis niloticus and Freshwater Prawn Macrobrachium rosenbergii Stocked at Different Densities in Polyculture Systems in Brazil

Abstract.— The effect of stocking prawns Macrobrachium rosenbergii at increasing densities in ponds with Nile tilapia Oreochromis niloticus reared at low density was evaluated. Twelve 0.01-ha earthen ponds were stocked with 1 tilapia/m² and 0, 2, 4, or 6 postlarvae prawn/m². Three replicates were randomly assigned to each prawn density. Postlarval prawns were stocked a week prior to tilapia juveniles and both were harvested 175 d after the beginning of the experiment. Tilapia final average weight, survival, production, and food conversion rates did not differ significantly among treatments ( P > 0.05); the averages were 531 g, 67%. 3,673 kg/ha, and 1.91, respectively. Prawn survival rates did not differ for the three stocking densities (mean 90%). However, final weight and production were significantly different ( P < 0.05) as follows: 34.0, 23.0, and 14.7 g and 639, 909, and 818 kg/ha, respectively for 2. 4, and 6 prawns/m² densities. Stocking densities up to 6 prawn/m² did not affect tilapia production and required neither additional feeding nor significant changes in management. The polyculture system allowed an increase in total production with the same amount of supplied feed, thus improving the system sustainability.     

Hatchery production of Florida red tilapia seed in brackishwater tanks: the influence of broodstock age

Abstract. Production of Florida red tilapia seed (eggs, sacfry and fry) in 34-m² above-ground tanks using recirculated brackishwater (12 ppt) was studied over a 5-month period on Lee Stocking Island (Exuma Cays, Bahamas). Four tanks were stocked with year class 1 (YCI) breeders, while 2 tanks were stocked with year class 2 (YCII) breeders at densities of 200 and 240/tank (5·9 and 7·1/m²), respectively, and at a sex ratio of 3 females to 1 male, beginning in November 1988. Seed production was measured by removing free-swimming fry from tanks and eggs and sacfry from the mouths of brooding females, and assessing the number of each at 15 to 16-day intervals from February to June 1989. Average seed production (seed/m²/day) was significantly higher in YCI (52·3) than in YCII (36·0) broodstock, indicating the advantages of replacing broodstock with yearling breeders each year.     

Effect of population density on the growth, feed and protein conversion efficiency and biochemical composition of a tropical freshwater catfish, Mystus nemurus (Cuvier & Valenciennes)

Abstract. Six groups of tropical freshwater catfish, Mystus nemurus (Cuvier & Valenciennes)(mean weight. 20·45 ± l·5g), were reared in 0·34m³ fibreglass tanks at different stocking densities (105, 195, 285, 375, 465 and 555 specimens/m³ water) for 84 days. The objective of the study was to determine the effect of various stocking densities on the growth, nutrition, biochemical composition and survival of M. nemurus. The lowest growth rate appeared in fish at the highest density and the highest was observed in fish stocked in moderate density of 285 and 375 fish/m³ water. Fish production was also lower at relatively low stocking densities of 105 and 195 fish/m³. Food conversion ratio (FCR), protein efficiency ratio (PER) and biochemical composition of M. nemurus indicate that there exists an optimum stocking density which lies between 285 and 375 fish/m³.     

Paddlewheel Effects on Shrimp Growth, Production and Crop Value in Commercial Earthen Ponds

The effects of continuous paddlewheel operation on shrimp growth, yield and crop value were studied in Hawaii. Six 0.4 ha earthen ponds were stocked with Penaeus vannamei at 25 postlarvae/m². Three ponds served as controls with no mechanical aeration or mixing. Each of the other three ponds had two 1 hp paddlewheel aerators (3.7 kw/ha) running continuously throughout the five month trial (29 April-8 October 1986). All other management factors were applied uniformly.
Daily water temperature and use were significantly different between treatments. Paddlewheel ponds had lower water temperatures (28.3 vs. 28.5 C) and lower water use (0.8% exchange per day vs. 2.2% exchange per day) than control ponds.
Faster shrimp growth in paddlewheel ponds was evident in week 8. At week 14, mean shrimp body weights and growth rates were significantly greater. Shrimp at harvest were 21.2 ± 2.6 g in paddlewheel ponds versus 15.3 ± 2.6 g in control ponds. Mean shrimp production was 2,852 ± 222 kg/ha in paddlewheel ponds compared to only 2,061 ± 558 kg/ha in controls. Mean crop value was $13,719 per pond per crop for paddlewheel ponds versus $9,111 for control ponds. Hence, paddlewheels afforded an increase of 42% in net crop value after subtracting purchase and operating costs.     

Use of night-lights to attract food organisms into tropical marine fish cages

Abstract. A 91-day cage trial was conducted with juvenile seabass, Lates calcarifer (Bloch), and grouper, Epinephelus tauvina (Forskal), to ascertain the capacity of kerosene pressure lamps and fluorescent electric lamps as night-lights above the cages to attract pelagic food organisms into the cage and consequently sustain the survival and growth of the cultured fish. The experiment was conducted using 1×1×1·5m floating cages with three different net mesh sizes (1, 13, and 19mm) and four fish stocking densities (seabass—10, 20,30 and 40/m³; grouper —10/m³). A positive growth response and survival was observed with seabass and to a lesser extent with grouper with increasing net mesh size and decreasing fish stocking density. At the lowest tested density of 10 fish/m³ seabass survival increased from 5·0 to 95·0% and total cage fish biomass increased from −95·1% to +56·9% with an increase in net mesh size from 1 to 19mm over the 91-day culture trial, respectively. The results are discussed in relation to the current commercial marine finfish cage farming practices employed in Indonesia.     

Growth and body composition of juveniles of Pterophyllum scalare (Lichtenstein) (Pisces; Cichlidae) at different densities and diets

Abstract. The effect on the growth of freshwater angelfish, Pterophyllum scalare (Lichtenstein) (Pisces; Cichlidae), of different densities of population and diet compositions was studied. The results show that increasing the population density from 50 fish/m² to 200/m² significantly decreased the rate of growth of fingerlings, and that this effect is correlated to the size of fish. No significant differences were observed in growth between diets containing 37%, 41% or 47% protein. However, the addition of live food (artemia) to the diet significantly raised the growth rate, especially in the higher protein diets.
Body composition shows no changes during the growth periods, with a mean of 64·68% body protein, 35·47% dry weight fat and no significant differences in the percentage of residual ash through the growth period.
The food conversion rate was very low, ranging from 1·15 to 1·31. Total production increased with density, from 4·0g/m²/day (50 fish) to 13·7g/m²/day (200 fish) over a period of 60 days.     

Use of Bagasse as a Feed Input to Semi-Intensive Shrimp Growout Ponds

Efforts to reduce the cost of growout feeds for aquaculture have traditionally focused on the use of agricultural wastes as direct or indirect nutritional supplements to support semi-intensive production levels. The merits of a low cost, sugar cane bagasse-based feed for semi-intensive production of Penaeus vannarnei were evaluated. Shrimp averaging 0.24 g each were stocked into 200 m² earthen ponds at 20/m² and cultured for a 12 week period. Two bagasse-based feed treatments, a manure-based treatment and a no-feed input control, were compared in replicate ponds. One bagasse treatment (artificial manure) was designed to mimic manure and stimulate autotrophic and heterotrophic growth. The other bagasse treatment (bagasse alone plus inorganics) was designed to stimulate primarily autotrophic growth. Both bagasse treatments produced average growth rates of 0.78 g/wk, which were significantly greater than that of the manure treatment (0.57 g/wk). Lack of difference between the two bagasse treatments suggests that additional supplements used in making artificial manure probably were unnecessary to the nutrition of the shrimp. At harvest, bottom organics in the bagasse-fed ponds were at least twice as great as manure-fed ponds, and may have contributed to the lower survival associated with these treatments.     

Effects of three dietary protein levels on the growth of pacu, Colossoma mitrei Berg, in cages

Abstract. Artificially reproduced pacu, Colossoma mitrei Berg, fingerlings (initial weight 41 g) were stocked (100/m³) in plastic cages (1·0m³) within a freshwater reservoir. Three diets containing 30, 35 and 40% protein were tested in quadruplicate over a 76-day experimental feeding period. Fish were fed 7 days a week, twice daily at a feeding regime of 4% body weight/day from stock to 100g and thereafter at 3% until harvest. Mean water temperature over the trial was 26·7°C. Significant differences were observed in total and daily gain and in protein efficiency ratio, while no differences were obtained in the feed conversion ratio between treatments. Based on this study a 35% protein ration is recommended for pacu within floating cages.     

Economic Feasibility and Risk Analysis of Australian Red Claw Crayfish Cherax quadricarinatus Aquaculture in the Southeastern United States

Australian red claw crayfish Cherar guudricurinutus are receiving increased attention from aqua-culturists, but have not been extensively investigated in terms of economic feasibility. In this study, research data from small pond experiments were combined with cost and return data to evaluate prospects for commercial production (50 ha scale) in the southeastern United States. Production data were derived from density experiments involving three initial stocking rates: "low" (l/m²), "medium" (3/m²) and "high" (5/m²). Experiments were conducted in nine 0.02 ha earthen ponds.
Risk analysis was used to simulate the range of potential outcomes that might be faced by producers. Results indicate that economic potential is most sensitive to the cost of juveniles, the percentage of the harvest biomass in the larger size classes, the price these classes receive, and the length of the growing season.     

Water Quality and Microbial Dynamics in Shrimp Ponds Receiving Bagasse-Based Feed

Pond water quality and associated microbial biomass were studied in relation to the type of feed applied during the culture of the marine shrimp Penaeus vannamei . The feeds tested included conventional feedlot manure as well as two feeds based on bagasse, a sugarcane waste product. Physical and chemical parameters were studied during a 100 day trial in 200 m² earthen ponds. Both bagasse-based feeds supported a significantly larger microbial community as measured by specific biomass numbers ( P < 0.01), ATP content ( P < 0.001) and amount of the particulate organic matter present on pond bottoms ( P < 0.025). For both bagasse-based treatments, the estimated bacterial cell number in the flocculent layer was 3.11 ± 10¹²/m², compared to the much lower cell number of 7.53 ± 10¹⁰/m² for control ponds. Harvest data suggest that bagasse forms a potential base for feeds when applied to extensive shrimp cultures.     

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.     

Growth and survival response of Penaeus stylirostris (Stimpson) to fertilization, pelleted feed and stocking density in earthen ponds

Abstract. Growth and survival response of Penaeus stylirostris (Stimpson) to fertilization, pelleted feeding and stocking density were analysed for the conditions prevailing on the Baja California peninsula (Mexico). Three 0·25-ha earthen ponds were longitudinally divided in half with mesh structures. One half received inorganic fertilization (trial F) and the other supplementary feeding using a pelletized ration (trial PF). The initial stocking rates were approximately 5, 10 and 15 PL5/m² in both trials. After 210 days, final mean weights ranged from 15·0 to 5·3g and survival from 48·6 to 17·8%. Growth and survival were analysed by means of a reparameterization of the von Bertalanffy's growth model and the exponential mortality equation. Results indicated that: (1) final mean weight was dependent on density in both trials ( P < 0·01) although growth rate was only affected in trial PF ( P < 0·01); (2) pelleted feeding produced both greater final mean weight and increased growth rate at densities higher than 5 PL/m² ( P < 0·005); (3) the ratio tail weight/total weight was influenced by density in trial F ( P < 0·015); (4) the mortality equation served to explain differences in survival to a limited extent. An increase in growth rate after 170 days occurring at the intermediate density in trial PF was attributed to an increase in mortality, which allowed the remaining individuals to attain larger sizes. Further research to increase biomass yields should focus on the optimization of pond depth, the supply of vigorous post-larvae and on the possible influences of seasonal variations of planktonic communities of the lagoons on the productivity of ponds.     

Effect of rearing density on the early growth and variation in growth of juvenile Arctic charr, Salvelinus alpinus (L.)

Abstract. Arctic charr, Salvelinus alpinus (L.), from the same full-sib family were reared under two different densities for 97days at 10°C. In one treatment density was adjusted every 2 weeks by means of a tank enclosure to a density of 50kg/m³. In the other treatment the density was allowed to increase as fish biomass increased to 50kg/m³. Density had no significant effect on the variation observed in individual fish weights over the course of the growth trial. Density had a significant effect on the relationship between fish weight and specific growth rate. The increasing density treatment had an overall higher mean specific growth rate of 0·1%/day.     

Disinfection, Microbial Community Establishment and Shrimp Production in a Prototype Biosecure Pond

Plankton community establishment and shrimp production in a prototype biosecure pond were compared to three control ponds. The biosecure pond was enclosed and intake water was disinfected, while control ponds were neither enclosed nor disinfected. All ponds were managed with no water exchange and stocked with 100 postlarvae/m², Litopenaeus vannamei . Residual oxidant concentrations in the biosecure pond dropped rapidly after cessation of chlorinated water addition. This was followed by a sharp increase in water column bacterial abundance, after which the pond was fertilized and inoculated with cultured Chaetocerous gracilis . After crash of the initial C. gracilis bloom in the biosecure pond, this species was not observed again. Following initial large fluctuations in biosecure pond bacterial abundance, phytoplankton biomass, oxygen consumption and nitrification rates, these parameters appeared to stabilize at levels similar to the control ponds. Early season compositional differences in phytoplankton, zooplankton, and bacterial communities were observed. No differences were seen in late-season phytoplankton and bacteria; however, zooplankton biomass tended to be lower in the biosecure pond than in the control ponds throughout the season. Shrimp production in all ponds was greater than 9,000 kg/ha. Production in the single biosecure pond was not a significant outlier compared to production in the triplicate control ponds.     

Effects of Stocking Density and Monosex Culture of Freshwater Prawn Macrobrachium rosenbergii on Growth and Production in Concrete Tanks in Saudi Arabia

Abstract This study was conducted to evaluate the effects of stocking density and monosex culture on growth, survival, yield and feed conversion ratio of freshwater prawn Macrobrachium rosenbergii in concrete tanks. Juvenile prawns with an average weight of 1.8 g were stocked into triplicate tanks at densities of 5, 10, 15 and 20 prawns/m², grown for 168 d and fed a 34% tilapia diet. Stocking density had significant effect on prawns. Final mean body weight decreased with the increasing density, being highest at 5 prawns/m² (29.6 9). and lowest at 20 prawns/m² (17.4 g). Total yield increased from 135 g/m² (1,350 kg/ha) at a density of 5 prawns/m² to 261 g/m² (2,610 kg/ha) at density 15/m^z to 245 g/m² (2,450 kg/ha) at 20/m^z. Feed conversion ratios were high and ranged from 3.7 (5 prawns/m²) to 5.6 (20 prawns/m²).
In monosex culture of freshwater prawns stocked in triplicate tanks at a density of 5 prawns/m² for 112 d, the all-male population had the best growth performance and feed conversion ratio, followed by the mixed-sex and all-female populations. The all-male population had 99% marketable prawns (>20 g) with an average yield of 159 g/m² (1,590 kg/ha); the mixed-sex population had 90% marketable prawns and the yield was 135 g/m^z (1,350 kg/ha); and the all-female population had 75% marketable prawns with an average yield of 108 g/m² (1,080 kgha).