Pond Conditions Research Articles

Hydraulic performance of mole drains and validation of steady-state drainage spacing equations for Mollisols

Central Santa Fe (Argentina) is a low-gradient region with impaired natural drainage. Extreme rainfall events are increasingly common and cause significant economic losses to agriculture. There is a growing interest in the use of mole drainage as a cost-effective strategy to mitigate such impacts. However, there is no information available that assists with mole drainage design, installation and maintenance, or the field assessment of a system’s hydraulic performance. This work was conducted with the dual objective of evaluating the hydraulic performance of an existing mole drains system and validating Hooghoudt’s steady-state drainage spacing equation for Mollisols. Three treatments representing different hydrologic conditions were tested; namely: (T1) rainfall of 360-min duration and intensity of 23 mm h-1, (T2) surface water ponding achieved through rainfall intensity of 50 mm h-1 and water depths between 50 and 100 mm, and (T3) similar surface water ponding conditions to treatment T2, but achieved through a rainfall intensity of 65 mm h-1 and either one (T3A) or two (T3B) sequential rainfall events. Following application of water, drainage commenced at 270 and 21 min for T1 and T2, and at 40 and 30 min for T3A and T3B, respectively. Mean drained depths were 1 and 3 mm for T1 and T2, respectively. For T3A, the mean drained depth was about one-third that measured for T3B (2.5 vs. 8.5 mm). Under a dry antecedent soil moisture condition, and rainfall intensity of 23 mm h-1, downward water movement was better described by piston flow. As surface water depth and soil water content increased, water flowed preferentially through the fissures and leg slots created by the mole plough implement at installation. Soil fissuring increased field hydraulic conductivity by factors between approximately three and ten. A 4 m mole drains spacing system was considered to be appropriate for managing excess water in the studied soil type. If the contribution of soil fissures to the field hydraulic conductivity can be accounted for, the Hooghoudt’s equation applied to two-layered soils may be used with confidence to help optimise the design of mole drainage systems for Mollisols. Application of this numerical approach, however, will require that the resultant spacing between mole drains be increased by about 30–40 %. Such an allowance will reduce installation costs and will not compromise the hydraulic efficiency of the drainage system.

Spatial variation of Physico-chemical parameters and water quality assessment of urban ponds at Raipur, Chhattisgarh, India

Water bodies, natural or man-made, are under threat due to rapid urbanization. This research paper assesses the water quality of 20 ponds located in the vicinity of urban habitats of Raipur district, Chhattisgarh (India) using the Water Quality Index (WQI). The samples were analyzed for 16 physicochemical parameters in the post-monsoon winter season. The parameters were used to calculate WQI and the ponds were categorized accordingly for end use purposes, that is, drinking, irrigation, industrial, or unfit for use without treatment. The WQI of post-monsoon samples resulted in that 75% of the total pond water samples are in excellent condition, & 25% of the samples are unfit for various activities like drinking, irrigation, industrial & domestic. A high value of nutrients was observed in all the ponds, suggesting that the nutrient entering through surface runoff, solid waste disposal, and wastewater is entering the ponds. Our results conclude that all ponds require interventional steps to restore pond water quality and stop it from further degradation, determining which trophic state of the ponds may change in the future. The spatial monitoring of physical and chemical properties of pond water helps to predict, identify, and assess the natural condition of the urban ponds and their relation with the surrounding (environment) and helps in adopting rejuvenation measures.

PERANCANGAN DAN PEMBUATAN ALAT KENDALI PEMBERIAN PAKAN IKAN NILA OTOMATIS BERBASIS INTERNET OF THINGS (IoT)

Fish farming is a form of animal husbandry that is mostly done by the people of Indonesia, both in ponds, in rivers and in the sea, fish farming in ponds requires maintenance and regular feeding of fish. Pond owners must always monitor fish growth and pond conditions to increase fish yields. By utilizing Internet of Things (IoT) technology and using a microcontroller to assist in feeding then combined with mobile application devices and using Firebase as data storage in real time, to control commands such as feed scheduling, feed conditions and feeding status. This system is expected to facilitate feeding.

Direct effects of elevated dissolved CO2 can alter the life history of freshwater zooplankton

Dissolved CO2 levels (pCO2) are increasing in lentic freshwaters across the globe. Recent studies have shown that this will impact the nutritional quality of phytoplankton as primary producers. However, the extent to which freshwater zooplankton may also be directly affected remains unclear. We test this in three model species representative of the main functional groups of primary consumers in freshwaters; the water flea Daphnia magna, the seed shrimp Heterocypris incongruens and the rotifer Brachionus calyciflorus. We experimentally exposed individuals to three pCO2 levels (1,500; 25,500 and 83,000 ppm) to monitor changes in life history in response to current, elevated and extreme future pCO2 conditions in ponds and shallow lakes. All species had reduced survival under the extreme pCO2 treatment, but the water flea was most sensitive. Body size and reproduction were reduced at 25,500 ppm in the water flea and the seed shrimp and population growth was delayed in the rotifer. Overall, our results show that direct effects of pCO2 could impact the population dynamics of freshwater zooplankton. By differentially modulating the life history of functional groups of primary consumers, elevated pCO2 has the potential to change the evolutionary trajectories of populations as well as the ecological functioning of freshwater communities.

Analisis Resiko Usaha Pembesaran Lele Sangkuriang Probiotik Dan Non Probiotik (Study Kasus Usaha Lele Bapak Wahyu) Di Desa Karang Binangun II BMR OKU Timur

The catfish farming business is a fairly developed business in the fisheries sector of East OKU district. Enlargement of catfish on limited land with high stocking density and poor feed management will worsen pond water conditions due to accumulation of organic matter that is toxic to catfish which causes stress and causes various diseases. Currently, probiotics are being used in fisheries for disease prevention efforts. The probiotic application itself gave birth to different attitudes and opinions for sangkuriang catfish rearing actors in Karang Binangun II Village, a stronghold that responded positively to revealing that real results had been obtained, in fact reducing production costs and boosting productivity. Meanwhile, from the camps that disagree, arguing is only wasteful and detrimental.
 The average cost incurred for probiotic sangkuriang catfish enlargement per 100 m² in one production cycle is Rp. 16,017,705 with an average total receipt of Rp. 21,098,500 so that the average income of probiotic sangkuriang catfish enlargement is Rp. 5,080,795. while the average cost incurred on non-probiotic sangkuriang catfish enlargement per 100 m² in one production cycle is Rp. 16,228,200 with an average total revenue received of Rp. 19,239,500 so that the average income for raising sangkuriang catfish non probiotics is Rp. 3,011,300.
 The cost risk of probiotic sangkuriang catfish rearing the coefficient of variance is 0.0063 while nonprobiotic sangkuriang catfish rearing the coefficient of variance is 0.0277, this is due to the large production costs that must be incurred by non-probiotic sangkuriang catfish rearing farmers, such as fertilization costs, liming costs , the cost of immunostimulants, and the cost of feed.
 For the production risk of probiotic sangkuriang catfish rearing with a coefficient of variance of 0.0048, while the non-probiotic sangkuriang catfish rearing with a variance coefficient of 0.0729 The results of the analysis show that the production risk of probiotic sangkuriang catfish rearing is smaller than that of nonprobiotic sangkuriang catfish rearing. this is due to the large production obtained on the enlargement of probiotic sangkuriang catfish.
 On the income risk of probiotic sangkuriang catfish rearing the coefficient of variance is 0.14 while on non-probiotic sangkuriang catfish rearing the coefficient of variance is 0.31. The results of the analysis show that the income risk of probiotic sangkuriang catfish enlargement is smaller than non-probiotic sangkuriang catfish enlargement, this is due to the low production cost of probiotic sangkuriang catfish with high production yields so that the income obtained on probiotic sangkuriang catfish enlargement is high.

Ефективність використання «Бровадазолу-20» для лікування та профілактики постодиплостомозу

Purpose. To investigate the efficacy of the prevention and treatment of post-diplostomatosis in carp using Brovadazole-20 and to provide recommendations for its use in aquaculture. Methodology. The study was conducted during 2015-2021 in pond farms of Vinnytsia region. The object of the study were age-1+ carps. The disinvasive properties of different concentrations of Brovadazole-20 were studied at the Research Laboratory of Ichthyopathology of Vasyl Stus Donetsk National University. Brovadazole-20 was used in 10 experimental groups as a part of a medicated feed mixture (MFM) containing from 0.1% to 1.0% of the product by making a granular feed. The daily dose of MFM for treatment was 2.5% by weight of fish. Subjects were clinically observed for 56 days after drug administration with an interval of two weeks. On the 14th day, samples were taken again and examined, as in the diagnosis. Examinations of skin scrapings for postodiplostomosis metacercariae in age-0+ fish were performed until the disappearance of clinical signs of the disease. The efficacy of Brovadazole-20 was determined as changes in black spots of different sizes on the body and the results of microscopy of skin scrapings for metacercariae in age-0+ fish. Findings. The study showed that administration of Brovadazole-20 at low concentrations as a part of a therapeutic feed mixture for fish in the spring and summer did not affect the presence of detected metacercariae in the study objects. The highest content of metacercariae (68.7%) was observed on the 56th day of the experiment at a concentration of 0.1%. At the same exposure regime, but at a concentration of 0.5%, the content of metacercariae of digenean trematode Posthodiplostomum cuticola in the sample was only 18.7%, and clinical signs of the disease were absent at a concentration of 0.6%. Originality. For the first time in the Vinnytsia region, a study was conducted on the use of prophylactic and therapeutic product Brovadazole-20 in postdiplostomosis in carp reared in pond conditions. Practical value. The results of this work provide recommendations on the use of prophylactic and therapeutic product Brovadazole-20 for the treatment and prevention of postodiplostomosis in carp. Key words: parasites, water bodies, monitoring, Posthodiplostomum cuticola, Brovadazole-20

Optimization of stocking density of Gulsha (Mystus cavasius) in circular shaped net cages in pond conditions

Influence of stocking density on growth and production of Mystus cavasius (local name: gulsha) in circular shaped cages was studied in earthen pond conditions for a period of 90 days. The cages were uniform in size of 1.80 m3 and were stocked with gulsha fry at the rate of (i) 200 fry/ m3 (T1), ii) 300 fry/ m3 (T2), and (iii) 400 fry/ m3 (T3). No significant differences were observed among the treatments in weight gain {11.46±0.16g (T1); 11.40±0.14g (T2); 11.48±0.04g (T3)}, SGR {2.77±0.06 (T1); 2.70±0.10 (T2); 2.71±0.09 (T3) day-1}, and survival rates {87.3±6.6 (T1); 85.7±4.7 (T2); 84.9±5.4 (T3) %}. A significantly higher (p<0.05) gross production of 4.29±0.32 kg/ m3 in 90 days was obtained in T3 (400 fry/ m3) treatment compared to T2 and T1. The coefficient of determination values (r2) of length-weight relationship (LWR) was 0.95, 0.94, and 0.94 in T1, T2, and T3 treatments, respectively indicating a good linear regression between length and weight. The results demonstrate that the cage culture of gulsha in pond condition is possible where 400 fry/ m3 stocking density in circular shaped cages may be suitable for higher growth, survival and production.

Effects of a Popular Aquatic Pest Control Agent among Carp Aqua-culturists on Aquatic Microfauna Dynamics

Cypermethrin is gaining popularity among fish farmers community to control aquatic insect pests and ectoparasites. Effect of cypermethrin application at farmer select dose (@0.003 ppm) on aquaculture pests (Notonecta & small prawn) commonly found in tropical ponds along with fish fry was assessed. Effect of cypermethrin application on the composition and survivability dynamics of aquatic microfauna namely rotifer, copepod and cladocera for 8 days was studied in tropical pond conditions. Cypermethrin cause significantly higher mortality to notonecta and prawn compared to fish fry within 24 h of exposure (P<0.05).

Effect of mixed leaf litter of four mangrove species on shrimp post larvae (Penaeus monodon, Fabricius, 1798) performance in tank and mesocosm conditions in Bangladesh

Mangrove leaf litter is a potential source of nutrients for shrimp post larvae. To introduce mangrove trees in shrimp farms it is necessary to identify the combination of trees which is most beneficial for shrimp. The present study evaluated the effects of mixed leaf litter of four mangrove species (Avicennia officinalis (Ao), Sonneratia apetala (Sa), S. caseolaris (Sc) and Heritiera fomes (Hf) on shrimp post larvae performance and water and soil quality. Leaf litter with and without supplemental feed was applied to shrimp culture tanks according to a 4 × 2 factorial design and followed by testing a subset of treatments in mesocosm pond conditions. Shrimp post larvae of 15-days old (PL15) with an average weight of 0.01 g were used for both experiments, each with a 4-week duration without water exchange. Under controlled conditions in the tanks, leaf litter and feed resulted in 22 to 32% higher weight gain of PL shrimp than combined weight gain realized when receiving only leaf litter or only feed, indicating synergism. Based on this, the pond experiment was designed with combined application of leaf litter and feed. The pond experiment resulted in higher shrimp weight gain than realized in the tanks. In tanks, the highest average individual weight gain of PL was observed for the leaf litter mixture SaAoHf (0.23 g)followed by SaScHf (0.21 g), ScAoHf (0.21 g) andSaScAoHf (0.20 g). Paralleling the results of the tank experiment, SaAoHf leaf litter also gave the highest average individual weight gain (1.2 g) of PL shrimpin the ponds but other leaf litter treatments followed by SaScAoHf (0.95 g), ScAoHf (0.84 g) and SaScHf (0.69 g) leaf litter. The different mixtures of mangrove leaf litter also resulted in significant differences in biological oxygen demand (BOD5), phytoplankton and zooplankton concentrations in pond water and organic carbon in soil. Both phytoplankton (P < 0.01, Pearson correlation r = 0.910)and zooplankton (P < 0.05, r = 0.535) abundance was positively correlated to shrimp weight gain. The low feed conversion ratio (FCR) in the treatments combining leaf litter and supplemental feed as compared to treatments using only feed indicated extra food benefits for shrimp PL from decomposing leaf litter. Overall, mixed mangrove leaf litter had a positive effect on shrimp performance and this effect was highest for SaAoHf leaf litter.

The effectiveness of using the synbiotic drug “ProStor” as additives in compound feed when growing carp fingerlings in pond conditions

The stimulating effect of the synbiotic drug “ProStor” on the body weight gain of fish and their physiological state was previously considered in various scientific sources when growing various fish species in swimming pools, cages and experimental aquariums. With the intensification of pond fish cultivation with compacted carp plantings, the percentage of natural forage organisms in the food lump is minimized, and, accordingly, the main weight gain of fish is carried out by feeding with compound feeds. In such conditions, the importance of using probiotic supplements in carp feeding becomes relevant. For a more complete description of the stimulating effect of probiotics, studies were conducted on feeding carp fingerlings in pond conditions of the Saratov region using the synbiotic drug “ProStor”. As a result of the conducted studies, it was revealed that the fish productivity of the outgrowth pond, where young carp were fed mixed feed with the drug “ProStor”, was 20% higher than in the control pond. Higher fish productivity was accompanied by better indicators of carp fingerlings by their average weight, which was 29.6 g and 26.4 g, respectively, in the experimental and control outgrowth ponds. In addition, the use of the developed drug by the company “STC BIO” LLC allowed to reduce feed costs when growing carp fingerlings, which indicates an increasing factor on the quality of compound feed of the synbiotic drug used. On average, the economic efficiency of the use of “ProStor” additives allows you to get an additional profit from one hectare of pond area compared to the control up to 22.5 thousand rubles.

Influence of pH on Water Hyacinth Ponds Treating and Recycling Wastewater

This work has examined the effects of pH on the treatment efficiency and biomass production rate of water hyacinth ponds (WHP) treating domestic wastewater. Experiments were carried out outdoor in WHP, working under batch and subtropical environmental conditions, using pre-treated sewage with pH varying from 5 to 9. It was observed that the plants regulated the pH of the medium to within 6.4 to 7.1 during the treatment processes independently of influent wastewater pH ranges. This adjustment reduced the treatment performances and the biomass production in ponds, the alkaline conditions in ponds being less favorable to the activities of the plants. The optimal removal and biomass production was achieved with influent pH of 7 lying in the above interval. So the optimum influent pH for the growth of plants and the removal of nutrients and organic matters in WHP is within pH 6.4 to pH 7.1.

Ecological assessment of the condition of fish ponds in the growing of carp fish in Kherson region

Ecological assessment of the condition of fish ponds in the growing of carp fish in Kherson region

Effect of Different Dietary Protein Levels on Physio-metabolic Response during Stunting of Milkfish, Chanos chanos (Forsskal, 1775) Reared under Pond Conditions

Background: Stunting is a process of suppressing growth from unfavourable conditions. The protein supplementation during stunting gives scope to maintain the nutrient reserves of fish and its quality. Methods: A feeding trial was conducted for eight months to study the effect of three hetero-nitrogenous diets with 25% (control), 30% (T1) and 35% (T2) crude protein (CP) levels on growth and physio-metabolic responses of Chanos chanos fingerlings during stunting. Milk fish fingerlings with a mean body weight of 11.71±0.18 g were stocked in earthen ponds @ 20 no/m2 in each replicate (n=3) was fed @ 2% biomass throughout the experiment. Result: Fish fed with T1 diet showed better specific growth rate (0.64±0.01% d-1), weight gain percentage (362.56±14.95) and protease activity (7.53±0.25 U/mg protein). Whereas, lower activity was observed for the enzyme assay, namely superoxide dismutase (45.41±2.50 U/min/mg protein), aspartate aminotransferase (34.01±1.88 U/min/mg protein) and alanine aminotransferase (39.64±0.64 U/min/mg protein). Hence, it may be concluded that the dietary protein inclusion level of 30% CP showed better growth performance and lower physio-metabolic response in milkfish fingerlings during the stunting.

Does Fish Conditioning in Aquaculture Increase Survival Success in the Wild? A Case Study on a Cyprinid Fish

Many endangered fish species in the wild are artificially bred, and their populations are strengthened by the stocking of aquaculture-raised juveniles. Because fish from aquaculture are generally not well prepared for the challenging life in the wild, we tested whether training for selected challenges could improve fish survival after stocking. We chose conditioning on predation pressure (by learning predator image of northern pike Esox lucius using predator chemical cues and visual stimuli), increased rearing water velocity 20 cm × s−1, and direct exposure to predation. The juvenile cyprinid fish asp (Leuciscus aspius) was used as a model prey species. A total of 7949 asp were reared in four groups using a combination of high flow, predation, and control treatments (low flow, no predation; 2018, 2149, 1929, and 1856 individuals, respectively). Of these, 1800 individuals were released into three ponds with pike, and their mortality rates were monitored in relation to predation for two months after stocking using passive telemetry arrays. The remaining 6149 aquaculture-reared individuals were released directly into a large reservoir, while 1426 individuals that survived pike predation for two months were released after the pond experiment ended. Fish survival in a reservoir was monitored in 2020 and 2021 by boat electrofishing and passive telemetry. The effect of training in aquaculture was not detected in pond conditions, but the fish that survived direct predation from pike for two months in the semi-natural treatment were more likely to survive in the wild than their aquaculture-reared counterparts. In the laboratory environment, asp responded to predator chemical cues with an increase in shoal cohesion and swimming activity, which demonstrate their ability to detect chemical cues. However, exposure to more fluvial conditions did not result in increased critical swimming speed. The study suggests that conditioning tested in aquaculture may not be sufficient to prepare fish for the wild, while exposing fish to direct predation could increase fish survival.

Infiltration under Ponded Conditions

Ponded infiltration processes occur in agricultural lands irrigated by flooding of their soil surface or under insufficient drainage conditions. The existing equations describing the phenomenon of vertical infiltration under ponded conditions have not considered the actual contribution of the pressure head gradient to the flow. In this study, simple equations are proposed to describe the horizontal and vertical infiltration under various ponding heads incorporating the actual contribution of the pressure head gradient to the flow. Six soils with known hydraulic properties, covering a wide range of soil textures, were used. Horizontal and vertical infiltration data are obtained by numerical simulation for all soils studied using the Hydrus-1D code. To validate the accuracy of the proposed equations, the solutions of horizontal and vertical infiltrations provided by the proposed equations were compared with numerically simulated ones provided by the Hydrus 1-D. The analysis of the results showed a very good agreement in all soils studied. The proposed vertical infiltration equation was also compared to a simple and accurate equation which does not incorporate the actual contribution of the pressure head gradient to the flow and differences between them were observed in all soils studied.

On the issue of Australian crayfish cultivation in ponds to ensure sustainable aquaculture development

The authors of this article describe the experience of biotechnology for growing Australian crayfish in conditions of pond cultivation in a group of ponds, operating in an intensive mode, used in an isolated area close by a natural water source in the Astrakhan region. In the presented article, research is aimed to clarify the main biotechnological indicators that increase the efficiency of cultivation in pond conditions. The conditions of transportation, the duration of transportation, and the density of crayfish in ponds with an area of 1 hectare have been clarified. The presented food recipe with the specification of the percentage of nutrients as additional feeding, organized when growing in ponds according to the food recipe itself, increases not only the growth rate but also the hemolymph protein concentration, which indirectly proves the satisfactory conditions for keeping aquaculture objects. Monitoring for the biotechnology of growing Australian crayfish in pond conditions: own developed food recipe, biological and physiological testing of key indicators such as hydrochemical indicators of water, hydrobiological indicators of the concentration of, and physiological indicators for determining the so-called biotechnological norm, which will add additional missing information on this aquaculture object.

Composition of Plankton in Water and Stomach Milkfish at Brackish Water Ponds

Abstract- Milkfish which cultivated in brackish water ponds utilize plankton as their natural feed. This study aimed to compare the abundance and type of phytoplankton, zooplankton in waterand stomach milkfish also the water quality of brackish water ponds. This research uses survey method, samples were taken in 3 brackish water ponds. The composition of phytoplankton wasfound in three brackish water ponds with 4 divisions, in the fish stomach 6 divisions, zooplankton composition was founded 2 divisions and fish stomach 2 divisions. Milkfish consumed allcomposition of plankton in water. Based similarity index of plankton composition in water and stomach milkfish about 73%-80%. The water quality of the three brackish water ponds is classified as oligotrophic, abundance of phytoplankton in the range of 630 - 1122 cell/ ml and zooplankton 0-30 ind/ml. Water qualities are classified as good for milkfish cultivation. Therefore, it is recommended to keep the good condition of brackish water ponds.

Application of sludge collector in super-intensive Vannamei shrimp farms

The solid organic waste load that is formed during the vannamei shrimp cultivation process is a problem that must be overcome because it triggers water quality deterioration and the emergence of shrimp disease. The sludge collector is designed to accommodate a load of the solid waste easily removed from the pond environment during the cultivation process. This study evaluates the performance of two types of pond outlets on water quality and shrimp production performance. Two concrete pond plots with an area of 1000 m2 each were used in this study. The treatments applied are the Sludge Collector and Central Drain solar model as outlet facilities located in the middle of the pond. The stocking density of the fry is 500 PL/m2 and is maintained for 92 days. According to the feeding program, 38-36% crude protein content is given eight times daily. The water exchange was carried out in the morning and evening. The application of additives in the form of lime, molasses, and probiotics into the ponds was adjusted to the needs and development of pond water quality conditions. The parameters measured consisted of water quality, total bacteria, total hematocyte count, prophenoloxidase (proPO), growth, survival rate, production, feed conversion ratio, and analysis of shrimp production costs. Data is analyzed using descriptive statistics. The study results show that the Sludge Collector application in super-intensive ponds has better water quality (total ammonia nitrogen, nitrite, nitrate, and total suspended solid performance due to the cleaner sludge disposal system to maintain water quality conditions suitable for the life of vannamei shrimp. This response is in line with the performance of THC and proPO in shrimp in Sludge Collector ponds that have a lower stress level than in Central Drain ponds. The sludge Collector application resulted in an 8.25% higher gain than the Sludge Collector treatment with a larger shrimp size.

Influence of Cage Shapes on Growth and Production of Silurid Catfish (Mystus cavasius) in Earthen Pond

Influence of three cage shapes viz (i) rectangular ii) square, and (iii) circular on growth and production of Mystus cavasius (local name: gulsha) was studied in earthen pond conditions for a period of 120 days. Each of nine cages, which were made of polyethylene nets, had same internal area (1.80 m3) and stocked with M. cavasius fry at the rate of 300 m-3, following a completely randomized design. Fishes were fed with a commercial floating pellet feed (Mega 002) initially at the rate of 25% of average body weight, with a gradual reduction to 8%. Significantly higher (P&lt;0.05) average weight gain (AWG) of 13.49 ± 0.14 g, with specific growth rate (SGR) of 1.87% day-1, and the survival rate of 89.41% were recorded for gulsha reared in the circular cage compared to the other shapes. Rectangular and square cages resulted in a similar (P&gt;0.05) AWG of 10.29 ± 0.10 and 10.43 ± 0.25 g with survival rate of 80 and 83.61%, respectively. A significantly higher (P&lt;0.05) average total production of 4.05 ± 0.21 kg/m3 was obtained with circular cage compared to a similar production of 2.72 ± 0.28 and 3.08 ±0.29 kg/m3 (P&gt;0.05) in rectangular and square cages, respectively. In case of lengthweight relationship (LWR), the coefficient of determination values (r2) was 0.86, 0.90, and 0.85 in square, circular and rectangular cages, respectively indicating a good linear regression between length and weight in circular cages than square and rectangular cages. Taken together, these results indicate that circular cage is the best for growth, survival and production of gulsha culture in pond condition. Ann. Bangladesh Agric. (2020) 24(2): 59-68

Soil greenhouse gas fluxes from tropical coastal wetlands and alternative agricultural land uses

Abstract. Coastal wetlands are essential for regulating the global carbon budget through soil carbon sequestration and greenhouse gas (GHG – CO2, CH4, and N2O) fluxes. The conversion of coastal wetlands to agricultural land alters these fluxes' magnitude and direction (uptake/release). However, the extent and drivers of change of GHG fluxes are still unknown for many tropical regions. We measured soil GHG fluxes from three natural coastal wetlands – mangroves, salt marsh, and freshwater tidal forests – and two alternative agricultural land uses – sugarcane farming and pastures for cattle grazing (ponded and dry conditions). We assessed variations throughout different climatic conditions (dry–cool, dry–hot, and wet–hot) within 2 years of measurements (2018–2020) in tropical Australia. The wet pasture had by far the highest CH4 emissions with 1231±386 mgm-2d-1, which were 200-fold higher than any other site. Dry pastures and sugarcane were the highest emitters of N2O with 55±9 mgm-2d-1 (wet–hot period) and 11±3 mgm-2d-1 (hot-dry period, coinciding with fertilisation), respectively. Dry pastures were also the highest emitters of CO2 with 20±1 gm-2d-1 (wet–hot period). The three coastal wetlands measured had lower emissions, with salt marsh uptake of -0.55±0.23 and -1.19±0.08 gm-2d-1 of N2O and CO2, respectively, during the dry–hot period. During the sampled period, sugarcane and pastures had higher total cumulative soil GHG emissions (CH4+N2O) of 7142 and 56 124 CO2-eqkgha-1yr-1 compared to coastal wetlands with 144 to 884 CO2-eqkgha-1yr-1 (where CO2-eq is CO2 equivalent). Restoring unproductive sugarcane land or pastures (especially ponded ones) to coastal wetlands could provide significant GHG mitigation.