Earthen Ponds Research Articles

Transfer of maternal immunity using a polyvalent vaccine and offspring protection in Nile tilapia, Oreochromis niloticus

Background Vaccination is an effective and alternative means of disease prevention, however, it cannot be conducted on the offspring of fish. For this process to take place, the transfer of maternal immunity should be implemented. This study aims to determine the effectiveness of transferring immunity from the broodstock to the offspring using a polyvalent vaccine against Aeromonas hydrophila, Streptococcus agalactiae, and Pseudomonas fluorescens in Nile tilapia, Oreochromis niloticus. Methods Nile tilapia broodstock with an average weight of 203g (±SD 23) was reared in spawning ponds until mass spawning and harvested one week post-spawning for vaccination. After being vaccinated according to the treatment, each fish broodstock was reared in 3x3 m cages installed in an earthen pond with a density of 20 broodstock, consisting of 15 females and 5 males. The vaccine used was a formalin-killed whole-cell vaccine at a density of 1010 cfu/mL injected intramuscularly (i.m.) at a dose of 0.4 mL/kg fish. Nile tilapia was injected with a vaccine used as a treatment. Example include A. hydrophila monovalent (MA), S. agalactiae monovalent (MS), P. fluorescens monovalent (MP), A. hydrophila and S. agalactiae bivalent (BAS), A. hydrophila and P. fluorescens bivalent (BAP), P. fluorescens and S. agalactiae bivalent (BPS), and A. hydrophila, S. agalactiae, and P. fluorescens polyvalent vaccines (PAPS). While the control was fish that were injected with a PBS solution. The broodstock’s immune response was observed on the 7th, 14th, 21st, and 28th days, while the immune response and challenge test on the offspring was conducted on the 10th, 20th, 30th, and 40th day during the post-hatching period. The parameters observed consisted of total leukocytes, phagocytic activity, antibody titer, lysozyme, and relative survival percentage (RPS). Result The application of PAPS in broodstock could significantly induce the best immune response and immunity to multiple diseases compared to other treatments. The RPS of the PAPS was also higher than the other types of vaccines. This showed that the transfer of immunity from the broodstock to the Nile tilapia offspring could protect it against bacterial diseases such as A. hydrophila, S. agalactiae, and P. fluorescens. Conclusion The application of polyvalent vaccine A. hydrophila, S. agalactiae, P. fluorescens vaccines increased the broodstock’s immune response and it was transferred to their offsprings. Polyvalent vaccines derived from maternal immunity can protect offspring from disease up to 30 days of age. They were able to produce tilapia seeds that are immune to diseases caused by A. hydrophila, S. agalactiae, and P. fluorescens.

Evaluation of the antibacterial activity and protein profiling of Nile tilapia (Oreochromis niloticus) epidermal mucus under different feeds and culture systems (biofloc technology and earthen pond).

The mucus layers of fish serve as the main interface between the organism and the environment. They play an important biological and ecological role. The current study focuses on Nile tilapia epidermal mucus reared under different commercial feeds (coded A and B) and environments (biofloc technology and earthen pond systems). Crude protein levels in feed A and B were 30% and 28%, respectively. Water parameters in all culturing systems were suitable for tilapia throughout the study period. The antimicrobial potency of tilapia (n = 5 from each) epidermal mucus was tested invitro against human and fish pathogenic strains viz. Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Francisella noatunensis, and Aeromonas hydrophila. To determine the antimicrobial activity, zones of inhibition (ZOI) were measured in millimetres and compared with two antibiotics (chloramphenicol and ciprofloxacin). SDS-PAGE analysis was performed on skin mucus samples of tilapia to determine protein quantity and size (molecular weight). Results of tilapia skin mucus (crude and aqueous) revealed a strong antibacterial effect against all the selected pathogenic strains. However, variation has been observed in the mucus potency and ZOI values between the biofloc and pond tilapia mucus. The crude mucus of tilapia fed on feed A and cultured in the pond exhibited strong antibacterial effects and high ZOI values compared to the mucus of biofloc tilapia, aqueous mucus extracts and positive control chloramphenicol (antibiotic). The SDS-PAGE results showed that the high molecular weight proteins were found in the collected epidermal mucus of BFT-B (240 kDa) and EP-B (230 kDa). Several peptides in fish skin mucus may play a crucial role in the protection of fish against disease-causing pathogens. Thus, it can be utilized in the human and veterinary sectors as an 'antimicrobial' for treating various bacterial infections.

A comparative Study of Blood Physiological Characteristics in Common Carp Fish Reared in Earthen Ponds in Different Locations at the Tigris and Euphrates Rivers in Central Iraq

This study was conducted with the aim of showing the effect of location and water quality on the blood and physiological characteristics of Common Carp fish. This study was carried out in four different sites in central Iraq for the period from 1/June 2022 to 30/November 2022, where the sites of Dujail and Suwayrah at the Tigris River were used, and the sites of Fallujah and Al-Mahawel at the Euphrates River. 120 fish were collected from the four sites, 30 fish for each site, and some traits were measured. The physiology of fish blood represented by the number of red blood cells, white blood cells, compacted blood volume, and hemoglobin concentration. The findings revealed that there were very substantial changes in the amount of compressed blood, the number of red and white blood cells, and the number of red and white blood cells between the Dujail and Fallujah locations, as it recorded 2.0 cells × 10 6 / mm3 and 32.8 cells × 10 3 / mm3 and 38.4 cells, respectively, in the Dujail site, and it recorded 1.8 cells × 10 6 / mm3. mm 3 and 30.9 cells × 10 3 / mm 3 and 37.3, respectively, in the Fallujah site, while there were no significant differences between the sites of Al-Suwaira and Al-Mahaweel. The results showed that there were highly significant differences in hemoglobin concentration between Dujail, Suwaira and Fallujah, as it recorded 12.0, 11.1 and 9.0, respectively. While there were no significant differences between the site of Al-Suwaira and Al-Mahaweel in hemoglobin concentration.

A small boat for fish feeding

This study focuses on development of a solar-powered Arduino Mega-driven robotic boat designed for efficient fish feeding in aquaculture. By integrating IoT technology and a mobile app, the project aims to reduce labor costs and improve feeding practices while addressing challenges associated with manual feeding, which previously failed to adequately cover the entire pond area. The research specifically centers on Nile tilapia production. Experimental results show that the robot emulates manual feeding with an average response time of 1.82 s for feeding initiation and 2.17 s for movement initiation. It efficiently distributes feed across a 4000 m² area in 9 min, outperforming the manual method, which takes 32 min. Fish fed by robotic boat exhibit an 18.71 % weight gain compared to those fed by hand. The robotic boat farm consumes a total of 11.480 kg of feed to produce 7.6 kg, while the hand-fed farm required 16.185 kg of feed to produce 6.5 kg. This results in feed conversion ratios of 1.51 and 2.49, respectively. The study finds an overall cost reduction of 46.13 % due to decreased labor hours. We strongly recommend adopting this robotic boat for optimizing tilapia feeding in earthen ponds.

Effect of tarpaulin pond on the growth and haematology of catfish (Clarias gariepinus)

The present comparative study investigated the haematological and growth parameters of catfish reared in both earthen and tarpaulin ponds. The growth response of the fish in both ponds such as overall weight gain, production index, survival rate, daily weight gain and length gain in the fish samples were determined. The overall weight gain in the catfish grown in earthen pond was higher (800 – 1000 g) than those from tarpaulin ponds (600 – 800 g). The production index of fish from earthen pond was higher than those of tarpaulin pond. The survival rate was higher in earthen pond (100%) than tarpaulin pond (80%). Moreover, daily weight gain and length gain were higher in earthen pond (12.50 g and 50 cm) than tarpaulin pond (10.00 g and 30 cm) respectively. Also, the haematological parameters such as the packed cell volume (PCV), haemoglobin concentration (HB), Red Blood Cell (RBC), White Blood Cell (WBC) count and other blood parameters of each of the blood sample, were determined using 5-part differential Haematology Auto-analyzer (Mindray BC 5300 model).Catfish from earthen pond recorded the highest haemoglobin value (8.68±0.15 g/dL) than that of tarpaulin pond (7.78±0.03g/dL) this means that the oxygen carrying capacity of blood of catfish from earthen pond is higher than those of tarpaulin pond. Packed cell volume (PCV) value was recorded the highest in earthen pond (25.00%) again than that of tarpaulin pond (23.50%). Earthen pond recorded the least white blood cell (WBC) count (5268.30±54.03 x 103/L) compared to that of tarpaulin pond (6170.50±37.09 x 103/L). Red blood cell (RBC) count was recorded the highest in earthen pond (2.74±0.01 x 106/L) than that of tarpaulin pond (2.18±0.01x 106/L). Blood of catfish from tarpaulin pond recorded the highest neutrophils (60%) than that of earthen pond (53%). Earthen pond recorded the highest leucocytes (40%) than that of tarpaulin pond (37%). Also, monocytes counts are higher in earthen pond (7%) than tarpaulin pond (3%). In conclusion, the results of the present study indicated that the type of pond material used to rear fish can alter growth and haematological parameters.

Physicochemical parameters and plankton diversity in water from selected ponds within Makurdi Metropolis

Physicochemical parameters and plankton diversity in water from five (5) selected ponds was investigated. In the investigation, some physicochemical parameters of water, the composition and abundance of plankton were determined. Some of the parameters include temperature, electrical conductivity, pH, dissolved oxygen, nitrates and phosphate. The samples were collected and transported to the laboratory of the Department of Fisheries and Aquaculture, Joseph Sarwuan Tarka University Makurdi for analysis. The preserved plankton samples were observed using a digital Celestron compound microscope and digital Celestron cosmos dissecting microscope. A combination of keys and guides provided were used for identification of the plankton species. A total of 13 different plankton species, with a total abundance of 308 were observed. The most abundant species was Chlorella vulgaris with an abundance of 85 and was observed in all three pond types. This was followed by Scenedesmus acutus (45) which was observed only in the concrete and liner ponds. Paramecium was next and was observed only in the earthen and concrete ponds. The rest of the plankton species were observed in only one pond type. The physicochemical parameters for the selected earthen, concrete and liner ponds were also selected. The pH and dissolved oxygen were observed to be higher in the concrete pond and lowering the liner pond. The electrical conductivity and total dissolved solid were however lower in the concrete pond and higher in the earthen pond, both the temperature and turbidity were higher in the liner pond and lower in the earthen pond. The phosphate concentration was also higher in the linear pond and lower in the earthen pond, while the concentration of Nitrite was equal in both earthen and concrete pond with no amount observed in the liner pond.

“Sea rice”: From traditional culinary customs to sustainable crop for high-end gastronomy?

Seaweed cuisine is booming in Western countries, but the nutritional and culinary potential of seagrasses remains largely unexplored. Seagrasses, unlike seaweeds, produce seeds. In the case of Zostera marina its seeds (commonly known as “sea rice”) have historically been used an as staple food by indigenous cultures, such as Seri Indians. Very recently, great expectations have been raised, with worldwide media coverage, about the use of the seeds as a new ingredient in some avant-garde restaurant. This article provides basic information on the biology of Z. marina, especially with regard to reproduction by seeds (the valuable gastronomic ingredient). It is important to know what are the main bottlenecks for seed production and meadow growth if seeds are to be used as novel and sustainable ingredients. One way to achieve enough seed production for gastronomic purposes may be throughout the “domestication” (farming) in natural earthen ponds near coastal areas where meadows are currently very scarce, such as in the Bay of Cadiz. This domestication not only opens up gastronomic possibilities, but part of the seed production can be used to meadow restoration, boosting the local economy, sustainability and blue carbon removal, and making the binomial gastronomy-sustainability a reality.

Impact of Diethylstilbestrol on the Growth Characteristics of White Prawn, <i>Penaeus indicus (M. edwards)</i>

The effect of dietary diethylstibestrol (DES) on the growth performance of white prawn, Penaeus indicus, was investigated for a period of 85 days in earthen ponds. DES at 4 mg/kg produced significantly superior growth (p < 0.01), high feed converson efficiency and nutrient digestibility. The total and specific digestive enzyme activities were maximum in the prawns fed with 4 mg/kg DES. Carcass protein content was increasd due to DES treatment. Residual DES content of the treated prawns on the final day of the experiment had been metabolised and reduced to that of the normal level of the control groups on the 20th day after cessation of hormone diets. DES had stimulated the growth of P. indicus through enhanced feed intake, high digestive enzymes activity, better nutrient digestibility and protein synthesis.

Nursery-Rearing Trials of Giant Freshwater Prawn, <i>Macrobrachium rosenbergii</i>, in Earthen Ponds

Nursery-rearing trials of the giant freshwater prawn Macrobrachium rosenbergii were carried out in five newly-excavated earthen ponds of 400 m2 each wit stocking densities ranging from 16 to 28/m2. The prawns were fed daily with pelleted feed (30% crude protein) at 10% body weight. The juvenile prawns reached an average weight of 0.655 - 1.290 g after 46-50 days of rearing. The individual daily weight increments varied from 12.8 to 23.6 mg in different trials. Per cent survival in different ponds ranged from 52.80 to 85.20 with an average of 68.79.

Comprehensive analysis of Vibrio alginolyticus: Environmental risk factors in the cultured Gilthead seabream (Sparus aurata) under seasonal fluctuations and water parameter alterations.

This study aimed to investigate the relationship between seasonal variations, water parameters and the prevalence of Vibriosis in Gilthead seabream. A total of 160 Gilthead seabream fish were sampled over the course of 1 year from private earthen pond farms in the Suez Canal area and examined for abnormalities and internal lesions. Vibrio alginolyticus, the causative agent of Vibriosis, was isolated and characterized from the sampled Gilthead seabream fish. The study revealed a significant correlation between different seasons and the prevalence of V. alginolyticus, with lower occurrence during autumn. Analysis of water parameters showed that toxic ammonia concentration was not effective in distinguishing between positive and negative cases of V. alginolyticus. Dissolved oxygen showed weak predictive ability for the occurrence of V. alginolyticus, while temperature demonstrated moderate potential as a predictor of its prevalence. pH values, organic matter concentrations and salinity showed no significant association with the occurrence of V. alginolyticus. Experimental challenges highlighted the vulnerability of Gilthead seabream to V. alginolyticus and emphasized the impact of environmental factors, such as pH and toxic ammonia, on their mortality and survival. The study emphasizes the importance of considering seasonal changes and water quality parameters in managing V. alginolyticus in mariculture. It underscores the need for careful monitoring and control of environmental factors to ensure the health and well-being of cultured fish populations. The findings contribute to our understanding of Vibriosis management and provide valuable insights for developing effective strategies in the aquaculture industry.

The effect of novel aquaculture mode on phosphorus sorption-release in pond sediment

The emergence of aquaculture modes has brought considerable changes to the aquaculture landscape and profoundly influenced environmental processes. However, there is limited research on nutrient cycling in emerging aquaculture modes. This study investigated the characteristics and mechanisms of sediment phosphorus (P) sorption-release in traditional earthen pond culture (TEP) and pond-tank culture mode (PTC), which represents novel aquaculture modes. The results showed that under higher nutrient load, the PTC did not show significant differences in nutrient concentration in water and sediments compared to TEP. Although there are no significant differences in overlying water P concentration between the modes throughout the entire aquaculture period, the trends of its variation over time are different, which significantly affected the P sorption-release characteristics of sediment. Additionally, correlation analysis suggested that calcium-bound P and hot NaOH-extractable organic P may affect the sorption-release characteristics of sediment as active P fractions. The change in redox condition caused by enzyme-mediated organic matter decomposition (such as protein and lipids) is also an important reason for sediment P release. However, the P fractions and organic matter content showed no significant differences between the two modes. Sediment microbial analysis showed that TEP exhibited a significant dominance of inorganic P-solubilizing bacteria, especially Actinobacteria and Bacilli classes. PTC had a higher proportion of organic P-solubilizing bacteria, primarily in the Bacteroidia class. The quantitative results of the key functional gene phoD in organic P decomposition also showed that the abundance in PTC was significantly higher than that in TEP. This suggested that microbial differences may be another reason for differences in P sorption-release behavior. This study revealed the differences in P sorption-release characteristics and mechanisms between the TEP and PTC, which holds positive implications for water quality and pollution management in novel aquaculture modes.

Carbon footprint values as a climate change assessment criterion of the partial harvests of European seabass and meagre in earthen pond aquaculture

Abstract Turkey's Mediterranean aquaculture industry is the world leader in European seabass aquaculture and the European leader in meagre aquaculture. In this study, carbon footprint (CF) values of four partial harvests of European seabass in earthen pond aquaculture (EPES) and meagre in earthen pond aquaculture (EPM) were determined. The average values of total CF expended for EPES and EPM, which reached a final harvest weight of approximately 1,500 g in 1,061 and 633 days were 3.38 and 2.26 kg CO2e kg−1, respectively. The lowest and highest rates of CF expended on consumed compound diet (CFCD) were 63.92 and 65.59% in EPES, and 62.44 and 66.70% in EPM, respectively. The rates of CF general management were 32.0 and 33.57% in EPES and 30.98 and 34.98% in EPM, respectively. Against this high proportion of the compound diet, the second highest value was the lowest and highest proportion of partial harvests of electricity, 28.20 and 29.59% in EPES and 27.09 and 30.51% in EPM, respectively. CF input and CF output per kg values of meagre were decreased with increasing weight, therefore meagre can be defined as a species with high global food security and resilience against climate change.

Would dependency on fossil fuels affect food security and sustainable production in aquaculture? Cultural energy use and energy use efficiency for earthen pond European seabass (Dicentrarchus labrax L., 1758) production

Would dependency on fossil fuels affect food security and sustainable production in aquaculture? Cultural energy use and energy use efficiency for earthen pond European seabass (Dicentrarchus labrax L., 1758) production

Response of Different Fish Species to Highly Saline Water under Desert Climate Condition - Finding Options for Local Food Security

Fresh water shortage is indeed a global issue that affects many areas of the world, including desert regions like the Thar Desert of Pakistan. Recurring droughts have badly affected the marginal communities of these areas. The desert has wide spread lenses of saline groundwater. There is a pressing need for exploring ways to use saline groundwater and identifying alternative sources of livelihood under the prevailing conditions. Therefore, a research study on saline aquaculture was conducted. Twenty fish fingerlings (40-50 g) of the varieties namely rahu labeo (locally kurh’rho), silver carp, mrigal carp (morakhi) and grass carp were stocked into the earthen fish pond. Saline groundwater having electrical conductivity (EC) between 8.5 - 9.0 dS/m was used to fill the pond. The overall yield of silver carp was the highest (1275 g/fish) followed by grass (1093 g/fish), mrigal carp (965 g/fish) and rahu labeo (610 g/fish). However, meal yield of grass variety was the highest followed by mrigal carp, silver and lowest of rahu labeo. Silver carp varieties had 330 g/fish of egg in their bodies. Hence, for the massive fingerling development, silver carp is recommended for saline aquaculture. However, for meal production and high economic return, grass carp should be selected for saline aqua-culturing.

Assessment of Tilapia (Oreochromis spp.) Welfare in the Semi-Intensive and Intensive Culture Systems in Thailand.

Welfare assessments have risen to prominence in the aquaculture industry, with increasing awareness of their significance among stakeholders in Thailand. In this study, we conducted a welfare assessment of tilapia (Oreochromis spp.) farms in Thailand, focusing on health, environmental, behavioural, and nutritional indicators. Comparing semi-intensive (earthen ponds) and intensive farming practices (cage culture), we found significant differences in the overall health score, particularly at farm F due to a disease outbreak (Kruskal-Wallis, p = 0.01). Skin and fin scores varied across farms, indicating their potential as indicators of tilapia health. Environmental assessments revealed differences in transparency between the two culturing systems (Mann-Whitney, p = 0.02). During the harvesting process, tilapia behaviours indicated poor welfare across all farms. However, no statistically significant difference in overall welfare scores was found between the two culturing systems. Correlations were observed between nutritional, environmental, and health indicators, with negative correlations between fish density and water transparency (r = -0.87, p = 0.02), presence of inhabitants (r = -0.78, p = 0.04), feeding behaviours (r = -0.78, p = 0.04), and swimming behaviours during capture (r = -0.98, p = 0.001). These findings provide valuable insights to enhance tilapia-farming practices and welfare in Thailand.

Assessing the impacts of zeolite on water quality, growth performance, heavy metal content and health condition of farmed tilapia (Oreochromis niloticus)

The rapid expansion and intensification of tilapia (Oreochromis niloticus) aquaculture in Bangladesh results in an increasing tendency of administering more pharmaceuticals in fish health management. Hence, with the aim of investigating the effects of zeolite (a water and sediment treatment compound) on water quality, growth performance, hematology, gut microbial content, and heavy metal content of Oreochromis niloticus, an experiment was performed for 126 days in six experimental earthen ponds (each pond size is one decimal). The stocking density was 300 fry/decimal. Zeolite was applied directly into the water in treatment ponds at a rate of 200 g/decimal during pond preparation and 100 g/decimal/15 days intervals during the culture period as recommended by the manufacturing company. The results indicated that zeolite had a significant effect (p < 0.05) on all growth indices assessed in all three experimental stages (0–42 days, 43–84 days, 85–126 days) in treatment ponds compared to control ones, except condition factor (CF) at the first stage. Hematological results implied that the application of zeolite in treatment pond water had no significant effect on the red blood cell (RBC) and white blood cell (WBC) of experimental fish blood compared to the control. However, a significant effect on the blood glucose level and total viable count (TVC) of the experimental fish gut was observed due to the addition of zeolite in the treatment ponds. Zeolite supplementation in treatment pond water significantly reduced the concentrations of different heavy metals in pond sediment, water and fish flesh compared to the control. Therefore, zeolite could be recommended for administration in aquaculture. Further research is required to find out whether a higher or lower dose of zeolite improves the water quality, growth performance and health condition, and decreases the heavy metal content of fish or not.

Lipid profile and metabolic parameters of tilapia in the finishing phase in earth ponds or using biofloc technology

Tilapia is a species with great growth potential. Its production comes from a semi-intensive system, such as earthen ponds (EP). Recently, biofloc technology (BFT) appears as an option to intensify fish production. The objective of this work was to compare the organosomatic indices, biochemical parameters, and chemical composition of tilapia reared in EP and BFT. Fish were grown for 150 days, with an initial weight of ≅ 2 g and a final weight of ≅ 780 g. Thereafter, tissues and organs were collected to determine organosomatic indices and analyze biochemical parameters, fatty acid, and proximate composition. The carcass yield was higher for tilapia reared in EP than BFT. The production system did not affect the fish fillet yield. The other organosomatic parameters were higher for tilapia reared in BFT. Tilapia reared in EP showed higher content of crude protein and lipids in the fillet. In both production systems, there was no difference in the body lipid profile. Fish in BFT showed a higher concentration of glucose and ammonia in the muscle and amino acids in the liver. Fish reared in EP showed a higher concentration of lactate in the liver compared to those in BFT. In conclusion, the production system alters the metabolism of fish. The biofloc has a considerable amount of fatty acids, which can be considered in the formulation of diets for tilapia in this system.

Hydrogen peroxide as a mitigation against Microcystis sp. bloom

Microcystis sp. is a harmful cyanobacterial species commonly seen in earthen ponds. The overgrowth of these algae can lead to fluctuations in water parameters, including DO and pH. Also, the microcystins produced by these algae are toxic to aquatic animals. This study applied hydrogen peroxide (7 mg/L) to treat Microcystis sp. in a laboratory setting and in three earthen pond trials. In the lab we observed a 64.7% decline in Microcystis sp. And in our earthen pond field experiments we measured, on average, 43% reductions in Microcystis sp. cell counts within one hour. The treatment was found to eliminate specifically Microcystis sp. and did not reduce the cell count of the other algae species in the pond. A shift of the algae community towards the beneficial algae was also found post-treatment. Lastly, during the pond trials, the gill status of Tilapia and Giant tiger prawn were not affected by the H2O2 treatment suggesting this may be a good mitigation strategy for reducing cyanobacteria in pond aquaculture.

Research verification of four commercial scale split-pond designs

Split ponds are earthen ponds divided into two sections: a small fish-confinement basin and a larger water-treatment basin. Water is circulated between the two basins using a high-volume pump. Although split ponds have proven their potential to increase the productivity of earthen catfish ponds, various pumping systems have been used in commercial settings. Choice of the best pumping system requires systematic verification of production and economic performance at commercial scale. In this study, we evaluated four commercial-scale design variants of split-pond systems. These four designs were primarily differentiated by the mechanism of water circulation between the fish-confinement and the waste-treatment sections. The water-moving devices include the slow-rotating paddlewheel, modified-paddlewheel aerator, screw pump, and axial-flow pump. This study investigated the production, economic, and investment feasibility of these four split-pond designs under controlled conditions over multiple years. An economic engineering approach using standard enterprise budget analysis was used to develop estimates of annual costs and returns for producing foodsize hybrid catfish from four split-pond systems. The additional investment capital required for converting a traditional open pond to any of the four split-pond designs ranged from $54,400 to $71,150 per 4-ha pond. The cost of production of the four split-pond designs ranged from $2.02/kg to $2.37/kg and was less than the 3-year average fish price. Higher breakeven yields are required to cover total costs, indicating increased financial risk associated with these intensive-production systems. Net present value (NPV) was highest for the modified-paddlewheel aerator design ($223,893/4-ha pond) and lowest for the screw-pump design ($74,621/4-ha pond). Similarly, the modified-paddlewheel aerator design had the highest modified internal rate of return (31%) while the screw-pump design had the lowest returns (27%). The economic and investment feasibilities of the four split-pond designs were sensitive to the prices of fish and feed. All four designs were economically feasible under current economic conditions with the modified-paddlewheel design showing greater economic potential for adoption.

Dynamic of active microbial diversity in rhizosphere sediments of halophytes used for bioremediation of earthen shrimp ponds

BackgroundIn New-Caledonia, at the end of each shrimp production cycle, earthen ponds are drained and dried to enhance microbial decomposition of nutrient-rich waste trapped in the sediment during the rearing. However, excessive ponds drying may not be suitable for the decomposition activities of microorganisms. Halophytes, salt tolerant plants, naturally grow at vicinity of shrimp ponds; due to their specificity, we explored whether halophytes cultivation during the pond drying period may be suitable for pond bioremediation. In addition, plants are closely associated with microorganisms, which may play a significant role in organic matter decomposition and therefore in bioremediation. Thus, in this study we aimed to determine the impact of 3 halophyte species (Suaeda australis, Sarcocornia quinqueflora and Atriplex jubata) on active sediment microbial communities and their implications on organic matter degradation.ResultsDrying significantly decreased the microbial diversity index compared to those of wet sediment or sediment with halophytes. Microbial profiles varied significantly over time and according to the experimental conditions (wet, dry sediment or sediment with halophyte species). Halophytes species seemed to promote putative microbial metabolism activities in the sediment. Taxa related to nitrogen removal, carbon mineralisation, sulphur reduction and sulphide oxidation were significant biomarkers in sediment harbouring halophytes and may be relevant for bioremediation. Whereas microbial communities of dry sediment were marked by soil limited-moisture taxa with no identification of microbial metabolic functions. Nitrogen reduction in sediments was evidenced in wet sediment and in sediments with halophytes cultures, along with putative microbial denitrification activities. The greatest nitrogen reduction was observed in halophytes culture.ConclusionThe efficiency of sediment bioremediation by halophytes appears to be the result of both rhizosphere microbial communities and plant nutrition. Their cultures during the pond drying period may be used as aquaculture diversification by being a sustainable system.