Showing papers on "Polyculture published in 2005"
TL;DR: Evaluated impacts of crop sequencing on precipitation use and showed how crop sequencing can accentuate synergistic interactions among crops to take advantage of diversity in space (polyculture).
Abstract: Cropping systems will not be sustainable without change. Broad-scope problems associated with developing sustainable cropping systems are how to choose and sequence crops in cropping systems. Our objectives were twofold: (i) evaluate impacts of crop sequencing on precipitation use and (ii) show how crop sequencing can accentuate synergistic interactions among crops. Crop-fallow systems that developed in the Great Plains resulted in precipitation storage efficiencies of about 20% in the early 1930s to about 40% in the late 1980s. Integrated crop-livestock systems have been developed in the southern Great Plains to take advantage of bimodal annual precipitation pattern to produce high quality pigeonpea [Cajanus cajan (L.) Millsp.] forage during the noncrop period between winter wheat (Triticum aestivum L.) harvest and seeding. Pigeonpea can be grown after a mid-June winter wheat harvest since pigeonpea uses precipitation received from wheat harvest to late September and pigeonpea has a root system that allows it to use soil water below the effective rooting depth of wheat. In the central Great Plains, water-use efficiency of winter wheat was improved 18 to 56% by including broadleaf crop in a grass-based rotation. Cropping systems in the northern Great Plains tend to be more diverse, and research at Mandan, ND, suggests that seed yield of flax (Linum usitatissium L.) can be tripled with a safflower (Carthamus tinctorius L.)-flax crop sequence vs. a flax-flax crop sequence. Great Plains cropping systems of the future will not only need to take advantage of crop sequences through synergism, but also take advantage of the interactions associated with diversity in space (polyculture).
89 citations
TL;DR: The results suggests that small trade-offs in plant fitness due to general functional shifts at the microbial level can be significant for the outcome of competition in plant communities and thus diversity at much larger scales.
Abstract: A gradient of microbial diversity in soil was established by inoculating pasteurized soil with microbial populations of different complexity, which were obtained by a combination of soil fumigation and filtering techniques. Four different soil diversity treatments were planted with six different grass species either in monoculture or in polyculture to test how changes of general microbial functions, such as catabolic diversity and nutrient recycling efficiency would affect the performance of the plant communities. Relatively harsh soil treatments were necessary to elicit visible effects on major soil processes such as decomposition and nitrogen cycling due to the high redundancy and resilience of soil microbial communities. The strongest effects of soil diversity manipulations on plant growth occurred in polycultures where interspecific competition between plants was high. In polycultures, soil diversity reduction led to a gradual, linear decline in biomass production of one subordinate grass species (Bromus hordeaceus), which was compensated by increased growth of two intermediate competitors (Aegilops geniculata, B. madritensis). This negative covariance in growth of competing grass species smoothed the effects of soil diversity manipulations at the plant community level. As a result, total shoot biomass production remained constant. Apparently the effects of soil diversity manipulations were buffered because functional redundancy at both, the microbial and the plant community level complemented each other. The results further suggests that small trade-offs in plant fitness due to general functional shifts at the microbial level can be significant for the outcome of competition in plant communities and thus diversity at much larger scales.
72 citations
TL;DR: Litopenaeus vannamei showed to be a more voracious species and fed mostly on organic detritus and benthos in both culture regimes and had a more restricted sources of feed in the ponds.
Abstract: Zooplankton, macrozoobenthos and feeding habits of Litopenaeus stylirostris and L. vannamei in monoculture and polyculture semi-intensive experimental ponds were evaluated. Zooplankton was more abundant in monoculture of L. stylirostris (1002 +/- 670 organisms (org.) L(-1)) than in monoculture of L. vannamei (470 +/- 37 org. L(-1)), and polyculture (321 +/- 188 org. L(-1)). The main zooplanktonic groups were polychaeta larvae, nauplii, copepods and polychaeta. Macrozoobenthos was more abundant in polyculture (6898 +/- 11 137 org. m(-2)) compared with monoculture of L. stylirostris (3201 +/- 350 org. m(-2)) and L. vannamei (2384 +/- 3752 org. m(-2)). The main benthic groups were copepods, polychaeta, ostracods, nematodes and insects. Differences in feeding habits were found between species and regimes. Litopenaeus vannamei showed to be a more voracious species and fed mostly on organic detritus and benthos in both culture regimes. Litopenaeus stylirostris had a more restricted sources of feed in the ponds. The major component in the stomach content of both species was detritus. Macroalgae, sand, exuvia, formulated feed, prey and microalgae were minor components for both species (<7%). Ingestion of formulated feed was <4% for L. stylirostris and was not detected for L. vannamei. The stomach repletion rates were larger for L. vannamei (55.6% and 48.8%) than for L. stylirostris (43.75% and 44.89%). Litopenaeus stylirostris grew better in polyculture (10.3 +/- 3.4 g) that in monoculture (9.0 +/- 3.8 g). Litopenaeus vannamei grew better in monoculture (16.1 +/- 4.8 g) than in polyculture (13.4 +/- 4.5 g). For both species, feed conversion ratio was lower in polyculture.
48 citations
TL;DR: The relationship between species diversity and the stability and production of trophic levels continues to receive intense scientific interest, and positive facilitative effects among competing zooplankton increased the size structure of algae, increasing the relative abundance of large, grazer-resistant algae.
Abstract: The relationship between species diversity and the stability and production of trophic levels continues to receive intense scientific interest. Though facilitation is commonly cited as an essential underlying mechanism, few studies have provided evidence of the impact that indirect facilitation may have on diversity/ecosystem functioning relationships. In this laboratory study, we examined the effect of zooplankton species diversity on trophic structure (total algal and zooplankton biomass) and temporal stability of total zooplankton biomass. We utilized four species of pond zooplankton grown in either monoculture or in polyculture. When comparing responses in polycultures with responses averaged across monocultures, a positive effect of diversity on total zooplankton biomass was observed. This occurred as a result of positive facilitative effects among competing zooplankton. Daphnia pulex , a biomass dominant in monoculture, was negatively affected by the presence of interspecific competitors. In contrast, Diaphanosoma brachyurum , a species that performed poorly in monoculture, was strongly and positively affected by the presence of interspecific competitors, driving positive diversity effects on total zooplankton biomass. Positive temporal covariances among zooplankton were detected in several polyculture replicates, increasing temporal variability of total zooplankton biomass. However, this destabilizing effect was weak relative to effects of high biomass yields in polyculture which caused temporal biomass variability (as measured by the coefficient of variation) to be lower in polyculture relative to monocultures. Zooplankton diversity effects on total algal biomass were not detected. However, increased zooplankton diversity significantly altered the size structure of algae, increasing the relative abundance of large, grazer-resistant algae.
37 citations
TL;DR: In this paper, the authors investigated the impact of the rice biomass and the stocking of fish (a polyculture of Nile tilapia and common carp) on ammonium, nitrate and ortho-phosphate levels in the field floodwater and the interstitial water of the oxidised soil layer.
31 citations
TL;DR: The positive effect of common carp on rohu reported in previous experiments is confirmed and a stocking density increase of 10% common carp and 10% rohu would improve rohu growth rate and result in 50% higher rohu harvesting biomass and yield, which may help farmers to select their species stocking ratios.
Abstract: This experiment was carried out in the framework of a project to develop a viable fish polyculture technology under Bangladeshi conditions that allows simultaneous fish production of small indigenous species for the farmers' family consumption and of large carp species as a cash crop. The objectives of this experiment were to assess the effects on fish performance and on the environment of adding 20% large fish to the basic 'cash crop' carp-small fish polyculture consisting of 10 000 fish ha(-1) of the large carp rohu Labeo rohita (Hamilton), catla Catla catla (Hamilton) and common carp Cyprinus carpio (L.) at a species ratio 1:1:1, and 15000 fish ha(-1) of each small indigenous fish punti Puntius sophore (Hamilton) and mola Amblypharyngodon mola (Hamilton) (control). The treatment ponds were stocked with additional 2000 large fish ha(-1), either all rohu, or all catla, or all common carp, or half rohu and half common carp, or half catla and half common carp. The results obtained and the analysis of interactions through the food web that affect food resource availability of the different fish species and account for the trends and differences observed among treatments confirm the positive effect of common carp on rohu reported in previous experiments and show that a 20% increase in large carps stocking neither affect the survival of the large carps nor reduce harvesting biomass of the small fish for the farmer's family consumption. Increased stocking densities of each large carp species did not significantly reduce its own harvesting weight and mean growth rate, while significantly increased rohu and catla (but not common carp) harvesting biomass and yield. The complex relations between species led to inter- and intraspecific competition, which in some treatments increased growth or yield of one species and in other treatments of other species, so that the gains on one species and the losses on the other led to no significant total harvested biomass differences between treatments. Yet, the results herein reported may help farmers to select their species stocking ratios. Thus, if the main target of the farmer is rohu, then a stocking density increase of 10% common carp and 10% rohu would improve rohu growth rate (due to common carp) and result in 50% higher rohu harvesting biomass and yield. If the main target of the farmer is catla, then a 20% increase in catla stocking density would lead to 20% higher catla harvesting biomass.
31 citations
TL;DR: A significant interaction was evident with time between water quality variables such as pH and alkalinity, and other factors, including manure type and fish species composition, which was reflected in the difference between pig and cow manure treatments.
Abstract: One of the most important issues concerning fish-pond fertilization is the determination of the optimal amount of fertilizer to be applied to the pond system. Another important concern is the suitability of fish species for polyculture in order to optimize production. The dynamics of nutrients, phytoplankton, and fish is a complex subject and practitioners are often compelled to formulate solutions without detailed scientific and practical consideration. The primary objective of pond fertilization is to maintain an optimal nutrient concentration for sustained biological production. Current fertilization practices in the Asia-Pacific region include: a fixed rate of fertilization and fertilization based on water color. Individual pond ecology determines how fertilization affects pond productivity, not the pond's physical location in relation to international borders. There is no universal recipe of “maximal” fertilization rates due to pond-specific variability. There is also no clear guide in the l...
18 citations
TL;DR: Results of this study indicated that the fish ratio and manure type significantly influenced fish survival and biomass over time and the interaction between species ratio, pH, and alkalinity was found to be significant.
Abstract: There are questions remaining about many aspects relating to fish food, including, the type of organisms consumed, mechanisms of consumption, and the digestibility and nutritive value of plankton. Common practice has been to divide fish into different types according to foraging in natural habitats, that is, fish are described as feeding on phytoplankton, zooplankton, benthic animals, macrophytes, or detritus. The distinction between the different feeding habits is not always absolute. Although species such as rohu, Labeo rohita, mrigal, Cirrhinus mrigala(Indian major carp), and Nile tilapia, Oreochromis niloticus(African origin) are omnivorous, their adaptability in different climatic conditions varies. A study was carried out to determine the optimal stocking ratio of tilapia and Indian major carp (rohu and mrigal) and with common carp, Cyprinus carpio; silver carp, Hypophthalmichthys molitrix; and big head carp, Aristichthys nobilisin polyculture. Four ratios of Nile tilapia and Indian and Chi...
14 citations
TL;DR: An attempt was made to evaluate the production of grass carp polyculture when N:P were maintained through supplementary organic fertilization, which found the fish production was found to be significantly different for organic fertilizer, grass carp + organic fertilizer and inorganic fertilizer treatments.
Abstract: Efficient usage of fertilizers in organic or inorganic forms show conflicting results in terms of net fish production under various climatic conditions. Manures applied to polyculture ponds as organic fertilizer, require a process of decomposition before the nutritional contents are released, assimilated, and utilized by plankton. On the other hand, inorganic (chemical) fertilizers are granular and concentrated with primary nutrients. Major nutrients such as nitrogen (N) and phosphorus (P) readily dissolve in water in ionic forms of nitrate, ammonium and orthophosphate. The differences in fertilizer solubility (nutrient release rate) and decomposition processes (organic fertilization) make the water quality and biological response distinctively different in inorganic fertilizer applied ponds. Previous research has indicated that one grass carp, Ctenopharyngodon idella, can support the growth of three silver carp. This means the excreta of herbivorous fish can be utilized to fertilize the water an...
TL;DR: A closed recirculating system for shrimp-mollusk polyculture consisted of several shrimp ponds, a mollusk water-purifying pond and a reservoir, and satisfactory results were achieved.
Abstract: This paper deals with a new system of aquaculture, i.e., a closed recirculating system for shrimp-mollusk polyculture. The culture system consisted of several shrimp ponds, a mollusk water-purifying pond and a reservoir. During the production cycle, water circulated between the shrimp and mollusk ponds, and the reservoir compensated for water loss from seepage and evaporation. Constricted tagelus,Sinonovacula constricta, was selected as the cultured mollusk, and Pacific white shrimp,Litopenaeus vannamei, as the cultured shrimp. The main managing measures during the production cycle were: setting and using the aerators; introducting the probiotic products timely into the shrimp ponds; adopting a “pen-closing” method for controlling shrimp viral epidemics; setting the flow diversion barriers in the mollusk pond to keep the circulating water flowing through the pond along a sine-like curve and serve as substrate for biofilm; no direct feeding was necessary for the cultured mollusk until the co-cultured shrimp was harvested; natural foods in the water from the shrimp ponds was used for their foods. Two sets of the system were used in the experiment in 2002 and satisfactory results were achieved. The average yield of the shrimp was 11 943.5 kg/hm2, and that of the mollusk was 16 965 kg/hm2. After converting the mollusk yield into shrimp yield at their market price ratio, the food coefficient of the entire system averaged at as low as 0.81. The water quality in the ponds was maintained at a desirable level and no viral epidemics were discovered during the production cycle.
Journal Article•
TL;DR: The impact of aggressive behaviour of koi carp was conspicuous by the increased level of attack on goldfish in polyculture trials in both experimental batches, and the two species exhibited considerable variation in the extent and type of aggression displayed.
Abstract: Experiments were conducted to document behavioural responses of koi carp, Cyprinus carpio L., and goldfish, Carassius auratus (L.) to monoculture and polyculture conditions in aquaria. Two parallel experiments, otherwise involving similar experimental protocols, were carried out with two batches of fish, fed with live tubifex worm (first batch) and live zooplankton (second batch). Each of the trials, randomized with respect to treatment, yielded data on aggressive encounters (chases, nips), both in presence and absence of food. The two species exhib- ited considerable variation in the extent and type of aggression displayed, koi carp being the more aggressive species. Frequency of attack increased in the presence of food. The impact of aggressive behaviour of koi carp was conspicuous by the increased level of attack on goldfish in polyculture trials in both experimental batches.
Journal Article•
TL;DR: It is observed that if partial harvesting is made, polyculture of Indian major carps with small fish is a better proposition in terms of biological production.
Abstract: The role of small indigenous fish species (SIS) is very important in Bangladesh. These fishes provide food, nutrition, subsistence and supplementary income. Until recently, possibilities of culturing them in combination with the Indian major carps were unexplored. So, an experiment in this regard was carried out in the Field Laboratory pond complex of the Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh during June to November, 1999. Polyculture of Indian major carps with small indigenous fish mola (Amblypharyngodon mola), punti (Puntius sophore) and chela (Chela cachius) was conducted to evaluate the production potential. Five treatments with three replicates were tested. Indian major carps and small indigenous fish were stocked at the rate of 7,500 and 50,000 fish/ha, respectively. The highest production (2103 kg) was obtained in treatment-3 where Indian major carps were cultured with punti. It is observed that if partial harvesting is made, polyculture of Indian major carps with small fish is a better proposition in terms of biological production.
01 Jan 2005
TL;DR: The findings of the present study suggest that though monoculture of pangasiid catfish give higher fish biomass production but polyculture with silver carp is environmentally good and economically profitable.
Abstract: The production of fish and net economic return in pangasiid catfish (Pangasius hypophthalmus) monoculture and polyculture with silver carp (Hypophthalmichthys molitrix) in farmers' ponds were assessed. The experiment was arranged in three treatments each with three replications. The ponds were stocked with 30,000 fishes per hectare. In treatment 1 (T1) pangasiid catfish only, in treatment 2 (T2) pangasiid catfish and silver carp at the ratio of 1:1, and in treatment 3 (T3) pangasiid catfish and silver carp at the ratio of 2:1 were stocked. At harvest, production of fish was found significantly (p<0.05) different among the treatments, highest in T1 and lowest in T2. Though the total biomass production and total economic return was significantly highest in T1 than in T2 and T3, the net economic return was lowest because of the required highest input costs especially for supplemental feed and fingerlings, resulted the highest cost per unit yield (CPY in Tk/kg) in T1. Highest cost for supplemental feed required in T1 was due to highest quantity of feed required for the highest number of pangasiid catfish stocked in that treatment. The findings of the present study suggest that though monoculture of pangasiid catfish give higher fish biomass production but polyculture with silver carp is environmentally good and economically profitable.
01 Jan 2005
TL;DR: A closed recirculating system for shrimp-mollusk polyculture consisted of several shrimp ponds, a mollusk water-purifying pond and a reservoir, and satisfactory results were achieved.
Abstract: This paper deals with a new system of aquaculture, i.e., a closed recirculating system for shrimp-mollusk polyculture. The culture system consisted of several shrimp ponds, a mollusk water-purifying pond and a reservoir. During the production cycle, water circulated between the shrimp and mollusk ponds, and the reservoir compensated for water loss from seepage and evaporation. Constricted tagelus, Sinonovacula constricta, was selected as the cultured mollusk, and Pacific white shrimp, Litopenaeus vannamei, as the cultured shrimp. The main managing measures during the production cycle were: setting and using the aerators; introducing the probiotic products timely into the shrimp ponds; adopting a 'pen-closing' method for controlling shrimp viral epidemics; setting the flow diversion barriers in the mollusk pond to keep the circulating water flowing through the pond along a sine-like curve and serve as substrate for biofilm; no direct feeding was necessary for the cultured mollusk until the co-cultured shrimp was harvested; natural foods in the water from the shrimp ponds was used for their foods. Two sets of the system were used in the experiment in 2002 and satisfactory results were achieved. The average yield of the shrimp was 11 943.5 kg/hm2, and that of the mollusk was 16 965kg/hm2. After converting the mollusk yield into shrimp yield at their market price ratio, the food coefficient of the entire system averaged at as low as 0.81. The water quality in the ponds was maintained at a desirable level and no viral epidemics were discovered during the production cycle.
Journal Article•
TL;DR: Experiments were carried out to assess the growth of tiger shrimp (Penaeus monodon) and carps under polyculture practice particularly in hardwater seasonal ponds.
Abstract: Experiments were carried out to assess the growth of tiger shrimp (Penaeus monodon) and carps under polyculture practice particularly in hardwater seasonal ponds. The growth of tiger shrimp and carps were recorded for a period of 110 and 180 days respectively during December, 2002 to May, 2003. The growth rate of Penaeus monodon and carps under polyculture practice were 32g and 298g respectively. The production of shrimp and carps registered under polyculture practice were 25.750 kg/0.1 ha/110 days (a low stocking density of 1.5 nos/m2 ) and 135.450 kg/0.1 ha/180 days respectively.
01 Jan 2005
TL;DR: In this paper, an attempt was made to study the input-output relationships and economics of pangas monoculture and carp-pangas polyculture in Bangladesh, where the authors analyzed the production systems of two technologies and the effects of fingerling stocking and applications of feed and fertilizer on fisheries income.
Abstract: An attempt was made to study the input-output relationships and economics of pangas monoculture and carp-pangas polyculture in Bangladesh. By analyzing the data collected from 50 pangas farms and 55 carp-pangas farms, the study has investigated the production systems of two technologies and the effects of fingerling stocking and applications of feed and fertilizer on fisheries income. The data were collected from the fishermen of Trishal and Bhaluka of Mymensingh district, and Kahaloo and Adamdighee of Bogra district during 2001-02. For pangas monoculture, the stocking density was 31,561 per ha while it was 55,017 per ha in carp-pangas polyculture. Most of the farmers used urea, TSP and lime before stocking. Rice and wheat bran happened to be the most common feed ingredients for both types of culture in general. Other important ingredients used were mustard oil-cakes, rice polish, wheat flour, fish meal, bone meal, soybean meal and poultry litter. In terms of quantities, rice bran and wheat bran dominated the farmers list. Rice and wheat bran together constituted about 60% of all studied feeds. Feed cost constituted 59.13% of total costs for pangas monoculture and 67.44% for carp-pangas polyculture. Per ha productions of pangas and carp-pangas in a single culture cycle were 15,508 kg and 19,745 kg, respectively. Per ha gross profits were estimated to be Tk 310,311 and Tk 464,418 for pangas monoculture and carp-pangas polyculture, respectively. Net profit appeared to be Tk 264,216 per ha for pangas monoculture and Tk 416,509 per ha for carp-pangas polyculture. The BCRs calculated were 1.46 and 1.68 for monoculture and polyculture, respectively. The break-even costs per kg of fish were estimated at Tk 36.93 for pangas and Tk 30.93 for mixed species which was much lower than the prices the producers received. Break-even productions were estimated at 10,702 kg per ha for pangas monoculture and 11,784 kg per ha for carp-pangas polyculture. Fingerling and feed cost, and pond size significantly explained the variation of income from pangas monoculture. These factors have significantly influenced the income from the crop. Functional analysis shows that 1% increase in the feed cost might increase 0.51% of pangas income and 0.41% in carp-pangas income. No other inputs had shown this much of responses to increasing income from a fish.
01 Jan 2005
TL;DR: Results show that weed biomass, species richness and diversity of the weed community are significantly reduced by inter-cropping, but are not affected by the type of fertilization.
Abstract: This paper aims to evaluate the effects of the cover crop type (Vicia villosa monoculture vs. V. villosa and Hodeum vulgare polyculture) and the type of fertilization (organic vs. chemical) on the structure of the weed community (biomass, number of species, diversity and evenness) and its invasibility through the experimental introduction of Brassica sp. seeds as a target invader species. Results show that weed biomass, species richness and diversity of the weed community are significantly reduced by inter-cropping, but are not affected by the type of fertilization. In organic plots, the density increases and the complementary pattern of polyculture resource use reduces weed abundance and Brassica sp. invasion, while the rapid emergence and fast growth of weeds can explain the Brassica sp. invasion resistance in monoculture. In contrast, chemical fertilization favours Brassica growth.
01 Jan 2005
TL;DR: A study was conducted to determine the factors affecting adoption of pond polyculture in six villages of three districts namely Mymensingh, Bogra and Narshingdi in Bangladesh.
Abstract: A study was conducted to determine the factors affecting adoption of pond polyculture in six villages of three districts namely Mymensingh, Bogra and Narshingdi in Bangladesh. In Mymensingh, 75% pond owners adopted carp polyculture technology whereas in Bogra and Narshingdi only 16% and 25% pond owners, respectively adopted this technology for fish production. The production of fish per unit area was found to be 5 to 10 times higher in Mymensingh compared to that of Bogra and Narshingdi. Fish farmers identified three main problems affecting the adoption of pond polyculture viz. lack of input used in aquaculture, low fish yield and lack of credit facilities for pond polyculture. The technological awareness of the farmers directly contributed towards use of inputs in culture ponds. The positive impact of technological dissemination found on input use, fish yield and uplifted socioeconomic condition.
TL;DR: In this paper, the economic viability of implementing a Nile tilapia with Australian redclaw crayfish polyculture was analyzed using profitability indicators such as internal rate of return (IRR) and net present value of the investment (NPV).
Abstract: Tilapia culture in rural communities of the state of Yucatan, Mexico, has been increasing in recent decades. Polyculture of tilapia with other more commercially valuable species is an opportunity to substantially improve the economic yields of rural producers. The economic viability of implementing a Nile tilapia with Australian redclaw crayfish polyculture was analyzed using profitability indicators such as internal rate of return (IRR) and net present value of the investment (NPV). A bioeconomic model was developed to simulate three production densities (33/0, 33/20, tilapia and crayfish, respectively), accounting for investment recuperation in time horizons of 5, 10 and 15 years. The model includes a biological sub-model describing the growth of both organisms, a management sub-model that influences organism development and an economic sub-model describing the main input and output variables of the economic setting of tilapia producers in the state of Yucatan. The biological sub-model was parameterized using published experimental polyculture data from Israel. A thermal correction function was integrated into Von Bertalanffy’s growth model to include the effect of temperature of Yucatan on growth in both organisms. The simulations showed a notable improvement in profitability when farms adopt the polyculture strategy, particularly over the 5-year horizon. The NPV of this horizon was -$4,855.06, $7,923.33 and $1,519.88, Mexican pesos, to the tilapia monoculture, medium crayfish density polyculture and high crayfish density polyculture, respectively. The Nile tilapia with Australian redclaw crayfish polyculture shortens investment recuperation time and it inhibits the risk related to changes in tilapia sale price. The best of the three studied combinations was the medium crayfish density polyculture (33/10) in all time horizons.
01 Jan 2005
TL;DR: A quaculture is the farming and caring of aquatic organisms including fish, mollusks, crustaceans and aquatic plants under individual or corporate ownership.
Abstract: A quaculture is the farming and caring of aquatic organisms including fish, mollusks, crustaceans and aquatic plants under individual or corporate ownership. Aquaculture has been almost entirely responsible for the expansion of available food fish since 1988, with production doubling in inland waters over the last decade. However, the majority of the expansion in aquaculture production is from Asian countries, largely from China.
01 Jan 2005
TL;DR: Polyculture trials were conducted under semi-intensive conditions in earthen ponds in Trinidad using the following combinations of species: red hybrid tilapia and armoured catfish (Hoplosternum littorale), freshwater prawn (Macrobrachium rosenbergii), and tilapio and prawn.
Abstract: Polyculture trials were conducted under semi-intensive conditions in earthen ponds in Trinidad using the following combinations of species: (i) red hybrid tilapia and armoured catfish (Hoplosternum littorale); (ii) freshwater prawn (Macrobrachium rosenbergii) and armoured catfish; and (iii) tilapia and prawn. Stocking densities were: tilapia 25 000 ha-1; catfish 30 000 50 000 ha-1; and prawn 10 000 100 000 h-1. A 35% protein diet of pelleted ration in floating (for tilapia) and sinking (for catfish and prawn) forms were fed as a percentage of estimated biomass. Growout times approximated 5.5 months. Average maximum yields were as follows: tilapia and catfish 27 614 kg ha-1 yr-1; prawn and catfish 12 622 kg ha-1 yr-1; and tilapia and prawn 24 176 kg ha-1 yr-
01 Jan 2005
TL;DR: The efficiency of two floating aquatic macrophytes (water hyacinth and water lettuce) to improve the water quality of pig fann wastewater was studied in this article, where experiments were conducted by using pig faann wastewater at different dilutions (1: 1, 1:5 and 1 :9) as well as undiluted wastewater.
Abstract: The efficiency of the two floating aquatic macrophytes (water hyacinth and water lettuce) to improve the water quality of pig fann wastewater was studied. Experiments were · conducted by using pig fann wastewater at different dilution (1: 1, 1:5 and 1 :9) as well as undiluted wastewater. Water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes) grew well in the 1:5 dilution and 1:9 dilution wastewater. Hence, wastewater with 1:5 dilution was selected for the subsequent experiments for evaluating the nutrient removal efficiency of the plants in monoculture and polyculture. The water parameters evaluated in this experiment were water tempemture, pH, dissolved oxygen, ammonia-N, and total phosphorus. For plant contents, total nitrogen and total phosphorus were studied. Throughout the experiments, solar mdiation and surrounding tempemture were continuously monitored. The reduction mte for ammonia-N and total phosphorus followed first-order kinetics. In terms of percent reduction of total phosphorus, water hyacinth monoculture has the greatest perfonnance (62.98%), followed by polyculture system (54.45%). Whereas for percent reduction of ammonia-N, all the plant systems have similar efficiency whereby reducing the ammonia-N up to 99%. Moreover, water hyacinth monoculture could also improve the pig fann wastewater quality in tenns of the pH (pH 7.33) and dissolved oxygen (DO = 7.94mgIL). Therefore, water hyacinth monoculture would serve to be a better floating aquatic macrophytebased wastewater treatment system in nutrient reduction followed by polyculture and water lettuce monoculture.
01 Jan 2005
TL;DR: Results suggest that resource complementarity was partly responsible for the positive effect of species diversity on productivity, and four analytic methods were used for estimating the net outcome of complementary effects and the different levels of ecological interaction in a community.
Abstract: A number of observational, theoretical and experimental studies have indicated that local plant species diversity can have positive effects on ecosystem productivity; however, little is known about the ecological mechanisms that regulate this relationship. To investigate the relationship between plant species diversity and ecosystem productivity and the effect of resource complementarity on productivity, we established experimental communities containing different levels of diversity using nine cultivated annual plant species. To address questions of complementary resource use, we planted each species in monocultures as well as in different polycultures, which allowed us to evaluate complementary effects. Complementarity was assessed by using four analytical methods. The first two methods were tested for an absolute increase in productivity with increasing diversity. The hypothesis was that a polyculture would outperform the most productive monoculture of a component species, defined as overyielding effect 1 (OV_1), and a polyculture would perform better than the average yield of monocultures of the component species, defined as overyielding effect 2 (OV_2). The third method measured the relative yield of the polyculture, Relative Yield Totals (RYTs), and the last method measured the D value, the proportional deviation of the productivity of a polyculture from its expected value. The results indicated that, to a certain extent, species diversity showed a positive effect on community productivity. The relationship between species richness and community productivity could be represented by a quadratic equation y = -98.449x2 + 1 039.2x - 42.407 (R2 = 0.423). Large differences in productivity were found among treatments with similar levels of diversity indicating that species composition had an important impact on community productivity. Calculation of a complementarity index indicated that about 40% of the polycultures outperformed its most productive component monoculture, more than 95% of the polycultures performed better than the average yield of its component monocultures, and more than 50% of the polycultures had significant RYTs 1 and D 0. These results suggest that resource complementarity was partly responsible for the positive effect of species diversity on productivity. Complementarity, however, was not significantly related to species diversity. Four analytic methods were used for estimating the net outcome of complementary effects and the different levels of ecological interaction in a community. Each method had its advantages and disadvantages. Therefore, in assessing how complementarity influences ecosystem productivity, different methods should be integrated.
Journal Article•
TL;DR: The results showed that Ulva lactuca can effectively purify water, improve water quality and reduce effluent discharge by reducing nutrition level and replenishing dissolved oxygen into the fishpond.
Abstract: Total 150 juveniles of red sea bream Pagrosomus major and some of seaweed Ulva lactuca were cultivated in a fishpond with a volume of 10.0m×9.0m×1.6m for a one-year polyculture experiment. The results showed that Ulva lactuca can effectively purify water, improve water quality and reduce effluent discharge by reducing nutrition level and replenishing dissolved oxygen into the fishpond. The annual variation of dissolved oxygen was from 4.75 to 6.50mg·L~(-1), and ammonia-N was 0.017—0.093mg·L~(-1).The parameters remained relatively stable, within safe limits for the fish during the experimental period. Red sea bream can tolerate a high water temperature of 34.5℃ and lower seawater specific gravity of 1.0120. The survival rate was 87.3% and food coefficient was 5.1. The variation of body weight was 355—529g·ind~(-1), with an average of 427g·ind~(-1) at the end of the experiment. Total yields of red sea bream and Ulva lactuca were 55900g and 358000g respectively. Both the fish and the seaweed were healthy during polyculture experiment, without any diseases. Ulva lactuca is an excellent macro-alga as a regulator of water quality.