Experimental Ponds Research Articles

Predicting the competitive interactions and trophic niche consequences of a globally invasive fish with threatened native species.

Novel trophic interactions between invasive and native species potentially increase levels of interspecific competition in the receiving environment. However, theory on the trophic impacts of invasive fauna on native competitors is ambiguous, as while increased interspecific competition can result in the species having constricted and diverged trophic niches, the species might instead increase their niche sizes, especially in omnivorous species. The competitive interactions between an omnivorous invasive fish, common carp Cyprinus carpio, and a tropically analogous native and threatened fish, crucian carp Carassius carassius, were tested using comparative functional responses (CFRs). A natural pond experiment then presented the species in allopatry and sympatry, determining the changes in their trophic (isotopic) niche sizes and positions over 4 years. These predictive approaches were complemented by assessing their trophic relationships in wild populations. Comparative functional responses revealed that compared to crucian carp, carp had a significantly higher maximum consumption rate. Coupled with a previous cohabitation growth study, these results predicted that competition between the species is asymmetric, with carp the superior competitor. The pond experiment used stable isotope metrics to quantify shifts in the trophic (isotopic) niche sizes of the fishes. In allopatry, the isotopic niches of the two species were similar sized and diverged. Conversely, in sympatry, carp isotopic niches were always considerably larger than those of crucian carp and were strongly partitioned. Sympatric crucian carp had larger isotopic niches than allopatric conspecifics, a likely response to asymmetric competition from carp. However, carp isotopic niches were also larger in sympatry than allopatry. In the wild populations, the carp isotopic niches were always larger than crucian carp niches, and were highly divergent. The superior competitive abilities of carp predicted in aquaria experiments were considered to be a process involved in sympatric crucian carp having larger isotopic niches than in allopatry. However, as sympatric carp also had larger niches than in allopatry, this suggests other ecological processes were also likely to be involved, such as those relating to fish prey resources. These results highlight the inherent complexity in determining how omnivorous invasive species integrate into food webs and alter their structure.

Effect of initial planting on vegetation establishment in different depth zones of constructed farm ponds

Farm ponds can be constructed and maintained to improve biodiversity and ecosystem functions in agricultural landscapes. Understanding the initial establishment process of vegetation in different water depths and effects of initial planting on this process is important for pond restoration. In the present study, two experimental farm ponds with or without initial planting were monitored for 5 years after their construction. These two ponds maintained high nutrients over 5 years from the beginning. The unplanted pond showed a rapid vegetation establishment and had more species and higher percent vegetation cover in 2–3 years than the reference pond. Planting accelerated this process by 1 year. Most of the early established species appeared to have originated from seed banks and/or seed rains. The species and functional diversity tended to decrease consistently since pond construction in the planted pond but increase initially and then decrease in the unplanted pond. The time when species composition between the unplanted pond and the planted pond became similar was delayed with the increase of water depth. Four years after pond construction, species composition was similar between the two ponds at all water depths. These results suggest that vegetation can establish quickly in farm ponds with fertile conditions and abundant seed sources through natural recolonization. The restoration approach for a farm pond should be decided considering the allowed time to success and the water depth. If the main goal of farm pond restoration is to improve species diversity, management practices may be more important than planting.

Utilization of alternative ingredients as combination feed on the growth of catfish (Clarias sp.)

This study aims to determine the effect of using alternative ingredients as a combination feed on the growth of catfish. This research was conducted in October - November 2020 which took place at the Laboratory of the Experimental Pond of the Departemen of Aquaculture, Sriwijaya University. The test fish used were catfish seeds measuring 5 - 6 cm. The study was designed with an experimental method in the form of a completely randomized design (CRD). The treatment to be used is a combination of commercial feed with alternative feed as many as 5 treatments with 3 replications, P0: commercial feed 100%, P1: combination of commercial feed 25% and alternative feed 75%, P2: combination of commercial feed 50% and alternative feed 50%, P3: combination of 75% commercial feed and alternative feed 25%, and P4: alternative feed 100%. Based on the results obtained, it shows that the use of alternative feed as a combination of feed has no significant effect on growth, feed efficiency and survival of catfish. The use of alternative feed as a combination feed of 50% (P2) has an effect on the growth and feed efficiency which is high in catfish of catfish. The growth of absolute length, absolute weight, and efficiency of fish feed produced were 1.67 cm, 4.20 grams, and 53.25%.

Impact of inclusion of hybrid red tilapia (Oreochromis mossambicus × O. niloticus), on total production in farm pond aquaculture

The present study was conducted to evaluate the impact of inclusion of hybrid red tilapia (Oreochromis mossambicus × O. niloticus) on productivity in carp based pond aquaculture. An experiment for a period of 270 days was conducted in two sets of earthen ponds (each of 0.132 ha size with 1.5 m depth). In Set I, five species viz. Catla catla, Labeo rohita, Cirrhinus mrigala, Ctenopharyngodon idella and Cyprinus carpio) were stocked (@13636 ha-1) in a respective ratio of 1:1:1:1:2. In Set II, hybrid red tilapia was included as additional species to other five carp species and stocked @ 13636 ha-1 in equal numbers. The seeds stocked (initial size 5-6 cm) were fed on commercial pellet feed having 20% protein, by broadcasting over the pond surface. The water quality parameters viz., temperature, pH, dissolved oxygen, alkalinity, nitrogen, phosphate and potassium remained more or less same in both the sets of experimental ponds. However fish growth parameters significantly differed in both the sets of experiments. Highest production of 2575.79±107.08 kg ha-1 was recorded in Set II followed by Set I with a production of 1894.32±428.44 kg ha-1. Tilapia stocked as an additional species provided a net estimated additional yield of 680.64 kg ha-1, which was 36.47% higher than that of Set I. The results of this study have proved significant impact of hybrid red tilapia inclusion on enhancing the net productivity. Keywords: Additional species, Farm ponds, Productivity, Red tilapia, Stocking density, Yield enhancement

Susceptibility of Channel Catfish (Ictalurus punctatus), Blue Catfish (Ictalurus furcatus), and Their Commercially Cultured Hybrid to Metazoan Parasite Infection in Earthen Pond Aquaculture

We herein document the metazoan parasite component communities of channel catfish (Ictalurus punctatus), blue catfish (Ictalurus furcatus), and their commercially cultured hybrid (female I. punctatus × male I. furcatus) communally stocked as parasite-free fingerlings into each of 3 experimental earthen ponds (each pond harbored channel catfish, blue catfish, and hybrid catfish). The fundamental objective of this work was to test the hypothesis that hybrid catfish exhibit less susceptibility to infection by metazoan parasites than do their parental species. Fingerlings of each catfish species from each pond were parasitologically examined monthly for 1 yr. A total of 112 channel catfish, 74 blue catfish, and 209 hybrid catfish were necropsied; collectively resulting in the detection of 14 metazoan parasite species. Channel catfish had the most diverse component community (12 species: 3 myxozoans, 2 monogenoids, 3 cestodes, 1 nematode, 1 unionid, and 2 copepods) followed by hybrid catfish (11 species: 3 myxozoans, 2 monogenoids, 2 cestodes, 1 nematode, 1 unionid, and 2 copepods) and blue catfish (6 species: 1 myxozoan, 2 monogenoids, 2 cestodes, and 1 copepod). These results do not support the assertion that hybrid catfish are demonstrably more resistant to parasitic infection than either parental species. New host–parasite records herein comprise Corallotaenia intermedia (Fritts, 1959) Freze, 1965, and Corallotaenia parafimbriata (Befus and Freeman, 1973) Scholz, de Chambrier, Mariaux, and Kucha, 2011 for channel catfish; Henneguya sp., C. parafimbriata, and Neoergasilus japonicus (Harada, 1930) Yin, 1956 for blue catfish; and Henneguya adiposaMinchew, 1977, Henneguya bulbosusRosser, Griffin, Quiniou, Khoo, and Pote, 2014, Ligictaluridus mirabilis (Mueller, 1937) Beverley-Burton, 1985, Ligictaluridus pricei (Mueller, 1936) Beverley-Burton, 1984, Essexiella fimbriata (Essex, 1928) Scholz, de Chambrier, Mariaux, and Kucha, 2011, C. parafimbriata, Spiroxys sp., Pyganodon sp., N. japonicus, and Achtheres sp. for hybrid catfish. To our knowledge, this is the most extensive parasitological study of this particular hybrid catfish, or any hybrid catfish, published to date.

Post feeding protection from Bilimbi to Motile Aeromonas Septicemia disease in African Catfish

Bilimbi (Averrhoa bilimbi) is plant medicinal used to control fish diseases both prevention and treatment. This study aims to determine the protection period of bilimbi-fed which different duration in catfish to enhance catfish (Clarias sp.) immunity in order to protect fish from Aeromonas hydrophila infection. The Randomized Block Design Factorial (RBDF) with 2 factors was used in this experimental. The first factor (A) was the period of feeding containing bilimbi juice consisting of 3 treatments, namely 0 days (P0), 7 days (P1), and 14 days (P2). The second factor (B) was the protection period after the administration of bilimbi juice to the infection of A. hydrophila bacteria consisting of 3 treatment, 5 days (T5), 10 days (T10), and (T15). This research was conducted at the Laboratory of Aquaculture Experiment Pond, Faculty of Agriculture, Sriwijaya University in October-December 2018. The parameters observed included prevalence of infection, growth, survival, feed efficiency and water quality. The result revealed that by giving 300 mL.kg-1 of bilimbi juice with different periods significantly affected the period of fish protection for A. hydrophila infection. The best prevalence value was 3,33% (P2T5), and the best survival of the fish before infection was 94,17% (P2), while the best fish survival post infection was 100% (P2T5), the best feed efficiency value was 56,47% (P2), water quality under experiment were 26-29,70C for temperature, pH 6.8-7.7, dissolved oxygen 4.35-5.37 mg/L and ammonia 0.09-0.21 mg/L.Keywords:Averrhoa bilimbiAeromonas hydrophilaEthnomedicinal plantFish immunityMotile Aeromonas Septicemia

Characterisation of myxozoan fauna of western mosquitofish, Gambusia affinis (Baird and Gerard) (Cyprinodontiformes: Poeciliidae), inhabiting experimental catfish ponds in Mississippi, USA.

Characterising myxozoan taxa parasitising fish hosts in catfish aquaculture ponds is crucial to understanding myxozoan community dynamics in these diverse and complex ecological systems. This work investigated the myxozoan fauna of the western mosquitofish, Gambusia affinis, a common, incidental species found in catfish aquaculture ponds in the southeastern United States. 598 fish were sampled in May of 2018 and 2019 from the pond facility of the Thad Cochran National Warmwater Aquaculture Center in Stoneville, Mississippi, USA. Fish were examined microscopically using wet mount preparations of fresh tissue and histology for myxozoans. 18S rRNA gene sequences were amplified from myxospores obtained at necropsy. Updated morphologic, histologic, and 18S rRNA gene sequence features are provided for Henneguya gambusi, Myxobolus pharyngeus, and Myxidium phyllium. Two potentially novel myxozoans were observed during this survey, an undocumented Myxobolus sp. associated with chondrolysis of bones throughout the body and a putative Myxobilatus sp. observed histologically in the renal tubules, ureters, and urinary bladder. However, inadequate samples were obtained for proper species descriptions. Lastly, the life cycle of M. pharyngeus, which is thought to utilize the oligochaete worm Dero digitata as their definitive host, was putatively confirmed by 18S rRNA sequence matching to actinospore stages from oligochaetes in catfish ponds in Mississippi. This work provides novel and expanded morphologic, histologic, molecular and biologic data of five myxozoan parasites of G. affinis, expanding our knowledge of myxozoan diversity in catfish aquaculture ponds.

Non-additive effects of foundation species determine the response of aquatic ecosystems to nutrient perturbation.

Eutrophication is a persistent threat to aquatic ecosystems worldwide. Foundation species, namely those that play a central role in the structuring of communities and functioning of ecosystems, are likely important for the resilience of aquatic ecosystems in the face of disturbance. However, little is known about how interactions among such species influence ecosystem responses to nutrient perturbation. Here, using an array (N=20) of outdoor experimental pond ecosystems (15,000L), we manipulated the presence of two foundation species, the macrophyte Myriophyllum spicatum and the mussel Dreissena polymorpha, and quantified ecosystem responses to multiple nutrient disturbances, spread over two years. In the first year, we added five nutrient pulses, ramping up from 10 to 50μg P/L over a 10-week period from mid-July to mid-October, and in the second year, we added a single large pulse of 50μg P/L in mid-October. We used automated sondes to measure multiple ecosystems properties at high frequency (15-minute intervals), including phytoplankton and dissolved organic matter fluorescence, and to model whole-ecosystem metabolism. Overall, both foundation species strongly affected the ecosystem responses to nutrient perturbation, and, as expected, initially suppressed the increase in phytoplankton abundance following nutrient additions. However, when both species were present, phytoplankton biomass increased substantially relative to other treatment combinations: non-additivity was evident for multiple ecosystem metrics following the nutrient perturbations in both years but was diminished in the intervening months between our perturbations. Overall, these results demonstrate how interactions between foundation species can cause surprisingly strong deviations from the expected responses of aquatic ecosystems to perturbations such as nutrient additions.

EFFECT OF COMMERCIAL FEEDS ON GROWTH AND PRODUCTION PERFORMANCE OF SHRIMP (PENAEUS MONODON) IN BAGERHAT COASTAL PONDS OF BANGLADESH

The experiment was conducted over 120 days from March to June 2019 in Bagerhat sadar upazila, Bagerhat. The study was categorized into four treatments indicated as T1 (ACI feed), T2 (Quality feed), T3 (Mega feed) and T4 (control) with three replicates. The experimental ponds were stocked with shrimp PL at same density of 4 nos./m2. Ponds were treated with agricultural lime based on soil and water pH and fertilized with urea and Triple Super Phosphate depending on water transparency and depth. Different water quality parameters were determined at ten-day intervals. Parameters of water were within acceptable ranges of shrimp culture. Higher growth (30.36 g) of shrimp was achieved in T2 compared to T1 (28.53 g), T3 (27.43 g) and T4 (22.85 g). Growth and survival rate of shrimp were comparatively lower in T4 at the same stocking density. Significantly (p<0.05) higher production of shrimp was obtained in T2 (971.52 kg/ha) than those of T1 (855.90 kg/ha), T3 (757.07 kg/ha) and T4 (566.68 kg/ha). Highest net profit (US$ 2570.2/ha) of shrimp farming was found in T2 than that of T1 (US$ 2105.7), T3 (US$ 1786.6) and T4 (US$ 1298.1). Results of the study indicate that among different commercial feeds Quality feed (T2) is better than other feeds in respect of survival rate, growth, production and net profit. So, farmers may be encouraged to use Quality feed for getting higher production and significant return in a short period of time.

High density aquaculture of white shrimp (Litopenaeus vannamei) in controlled tank

The study was aimed to evaluate the growth, survival rate and production of white shrimp (L. vannamei) culture under different stocking density in controlled tank. This research was conducted at Experimental Pond Installation. Research Institute for Coastal Aquaculture and Fisheries Extension in Maros Regency, South Sulawesi. Indonesia. Juveniles of white shrimp size in weight 0.14 g/ind were cultured for 70 days in three different stocking densities: 100, 200 and 300 ind/m3 in a total of nine fibre tanks sized of 2 m3. The study used Completely Randomized Design (CRD). with three replications for each treatment. The parameters observed were growth rate, survival rate, production, feed conversion ratio of white shrimp and water quality condition. The results showed that the different stocking density had a significant effect (P <0.05) on growth, survival rate and production of white shrimp. The final weight and absolute weight of vaname shrimp decreased as density increased to 300 ind/ m3. The final weight of vaname shrimp in treatments A. B and C were 13.70 g/ind, 12.27 g/ind and 10.90 g/ind respectively. Survival rate and production of white shrimp in this study ranged from 80-95% and 1.24-2.42 kg/m3 respectively. Water quality measured during the experiment was suitable for the growth of white shrimp.

The influence of ecological conditions on the growing of fingerlings carp hybrids of different origin

The article presents an analysis of the ecological condition of reservoirs of the cultivation system of the State Enterprise «Lviv Research Station of the Institute of Fisheries NAAS» to create optimal conditions in ponds for growing carp hybrids of different genesis. It was found that the hydrochemical regime in the experimental ponds did not differ much because it mainly depended on the chemical composition of the water source of their water supply. In general, the main hydrochemical parameters that characterize the quality of pond water meet the standards for fishery reservoirs. According to OO Alokin’s classification, the water corresponded to a weakly alkaline or alkaline medium (7.0–9.1) and belonged to the hydrocarbonate class (HCO3 — 152.5–222.0 mg/dm3), with a predominance of SO42–, (69.2–72.8 mg/dm3), with an average mineralization in the range of 319.0–402.5 mg/dm3. Temperature indicators corresponded to seasonal dynamics and were in the range of 15–26°C, with the maximum value in July, while the content of dissolved oxygen in water did not fall below 2.43 mg·O/l. Phytoplankton of experimental ponds was represented by freshwater species (from 62 to 80) belonging to 7 systematic divisions. Chlorophyta 10450 dominated in number — 2836.79 thousand cells/dm3. Quantitative indicators of phytoplankton development were at the level of 2773.59–18496.62 thousand cells/dm3 by number and from 0.78 to 3.32 mg/dm3 by biomass. Zooplankton of experimental ponds was mainly represented by organisms of three systematic groups: Rotifera, Cladocera and Copepoda. At the time of the research, the quantitative indicators of zooplankton development in growing ponds ranged from 22.0 to 257.0 thousand specimens/m3 in number, and 0.36–19.1 g/m3 in biomass. The main role in the formation of zooplankton biomass was win back by young forms of branched crustaceans. The obtained indicators of the ecological condition of fish ponds will create optimal conditions for fish farming. Accordingly, they contribute to the positive physiological development of this year’s carp hybrids.

Polyculture seaweed Gracilaria sp. and milkfish in the pond

Seaweed Gracilaria sp. and milkfish are euryhaline fishery commodities. Both of these commodities can be cultivated by polyculture in ponds. Polyculture is a mixed cultivation technology between two or more commodities that can increase aquaculture production and provide value added cultivators as it can harvest several products in one season. Polyculture seaweed Gracilaria sp. and milkfish are done at Marana Experimental Pond Installation, Research Institute for Coastal Aquaculture, Maros South Sulawesi with extensive technology system, using 1 plot of pond size 10,000 m2. Preparation of the pond begins with the repair of dikes, patching leaks and repair of sluices. Next is draining ponds, eradicating pests with 20 ppm saponin, pond flushing, subsequent fertilizing and preparation of water for dispersal. Initial fertilization is done by using Urea and TSP fertilizers with doses of 100 and 50 kg/ha. Seaweed seed stocking in ponds as much as 2,000 kg/ha was done in March using a broadcast method, i.e., seed stocked in all parts of ponds. The milkfish seeds are also stocked with a dense stocking of 1,000 tails/ha. The first harvest of seaweed can be done after the maintenance period of 3.5 months. The next harvest can be done every 30-45 days. Total production of dried seaweed reached 8,284 kg/ha (5 times harvest/year) and milkfish harvest reached 375 kg/ha.

Продуктивність та ефективність вирощування дволіток коропа (Cyprinus carpio (Linnaeus, 1758)) за використання в складі корму пребіотичної добавки

Purpose. The aim of the work was to assess the effectiveness and feasibility of using the prebiotic "Actigen" in the process of commercial cultivation of carp taking into account productive and economic indicators. Methodology. The study was conducted in 2019, using three ponds, two of which were experimental and one control, which were stocked with age-1 scaly carp with an average weight of 55 - 56 g at a stocking density of 1000 specimens/ha. Carp of the experimental groups were fed during 90 days of the growing season with a feed with supplemented with the prebiotic "Actigen" at the amount of 0.025% (Experiment 1) and 0.05% (Experiment 2). Optimal conditions for carp keeping were provided during the study with the control of oxygen, temperature, hydro-chemical and hydro-biological regimes of the aquatic environment and analysis of the efficiency of cultivation at the end of the growing season according to generally accepted methods in aquaculture. Piscicultural and economic indicators of age-1+ carp cultivation were determined at the end of the growing season. Findings. Conditions for growing carp in experimental and control ponds were satisfactory. No dependence of the hydro-chemical regime of experimental ponds on the composition of the diet was found. The average seasonal biomass of food organisms of zooplankton and zoobenthos during the growing season was 10.81 – 20.64 g/m3 and 0.47 – 0.73 g/m2, respectively, and served as an additional source of food for carp. It was found that the average weight of age-1+ carp, which was fed with the feed with the addition of 0.025% and 0.05% of prebiotic supplements, was higher by 11.9% and 22.2%, respectively, fish productivity – by 12.1% and 23.1%. The feed conversion rate was lower by 9.5% and 19.1% relative to the control. The cost of additionally obtained fish products when fish were fed with a feed supplemented with the prebiotic at the amount of 0.025% was 4290 UAH/ha, 0.05% - 8190 UAH/ ha. The contingent income, including costs for feeds and fish seeds using 0.025% and 0.05% prebiotic, was 20.9% and 33.6% higher, respectively, than in the control group. Originality. The effect of prebiotic "Actigen" on productivity and economic indicators in the process of growing age-1+ carp was studied for the first time. The implementation of this task provided an opportunity to increase the fish productivity of ponds by feeding fish with an artificial feed of improved composition. Practical value. The obtained results testify to the expediency and efficiency of using prebiotic "Actigen" in fish farming. Reducing the cost and obtaining additional gains in the cultivation of fish products is provided by improving the quality characteristics of feed. Key words: carp, prebiotic, "Actigen", hydro-chemical and hydro-biological parameters, fish productivity, feed conversion factor, efficiency, profit.

Performance of small Saltless Solar Pond Augmented by Planar Mirror.(Dept.M)

In the present study, the performance of a small saltless solar pond augmented by planar reflector is presented. Experiments are carried out in the Faculty of Engineering, Mansoura University, Egypt (31O N). The experimental pond has a surface of 1.23 m x 1.23 m and 0.83 m water depth. A glass mirror with 1.6 m height and 2.5 m width is supported in a common edge with the pond surface. The glass reflector is south facing and vertical in position. Plastic films are used as a top covers for the pond surface. Measurements of solar radiation, ambient temperature and water temperatures at different heights in the pond are carried out. Measured augmented solar radiation is compared with that predicted by the radiation enhancement model. The comparison has shown a good agreement between the measured and the predicted data. The temperature gradient through the storage zone of the pond ranges around 5 Co and the upper layer of water is highly dependent on the ambient conditions. Temperatures of the plastie layers are presented during the day time, and also during 1!ie build-up period. Water temperature on the pond surface of more than 60 °C could be attained in October, with a pond efficiency ranges from about 50 up to 66%.

Ontogenetic diversity buffers communities against consequences of species loss.

Biodiversity can be measured at multiple organizational scales. While traditional studies have focused at taxonomic diversity, recent studies have emphasized the ecological importance of diversity within populations. However, it is unclear how these different scales of diversity interact to determine the consequence of species loss. Here we asked how predator diversity and presence of ontogenetic diversity within predator populations influences community structure. Ontogenetic diversity arises from shifts in the traits and ecology of individuals during ontogeny and it is one of the biggest sources of intraspecific diversity. However, whether it dampens or strengthens the negative consequences of with species loss is poorly understood. To study the interaction of species diversity and ontogenetic diversity, we experimentally manipulated predator species diversity and diversity of developmental stages within focal predator species and analysed their joint effect on predator and prey survival, biomass and prey community structure in experimental pond systems. While individual effects of ontogenetic diversity were often species specific, losing predator species from the community often had a much smaller or no effect on prey survival, biomass or community structure when all predator populations had high ontogenetic diversity. Thus, ontogenetic diversity within populations buffered against some of the consequences of biodiversity loss at higher organizational levels. Because the experiment controlled mean per capita size and biomass across structured versus unstructured populations, this pattern was not driven by differences in biomass of predators. Instead, results suggest that effects were driven by changes in the functional roles and indirect interactions across and within species. This indicates that even if all environmental conditions are similar, differences in the intrinsic structure of populations can modify the consequences of biodiversity loss. Together, these results revealed the importance of ontogenetic diversity within species for strengthening the resilience of natural communities to consequences of biodiversity loss and emphasize the need to integrate biodiversity patterns across organizational scales.

Bioaccumulation and health risk assessment of phthalate esters in cultured low trophic level fish feded with food waste-based diets

The present study aimed at using different types of food waste as a protein source for the fish feeds to produce safe and quality fish. The results showed the concentrations of ∑PAEs in grass crap (0.24 μg g−1 ww) and bighead carp (0.15 μg g−1 ww) fed with Food waste B feeds (mainly containing fruit, vegetable and cereal waste) was significantly lower than those fed Food waste A feeds (mainly containing meat waste) and control feeds (p<0.05), and the highest ∑PAEs concentration (1.75 μg g−1 ww) was found in the mud carp fed with control feeds in experimental ponds (p<0.05). In addition, there was no biomagnification of PAEs in the food chains within the ponds. The health risk assessment results showed no non-carcinogenic and carcinogenic risks from the PAEs via ingestion of the fish fed with food waste feeds for the local residents.

Assessment of food intensity and growth rate young sevryuga (Acipenser stellatus Pallas, 1771) depending on from the terms of fishing of growing ponds

Artificial reproduction of sturgeon fish in the Volga-Caspian basin in modern conditions is the only real opportunity to replenish natural populations with juveniles, therefore, increasing its efficiency is the key to restoring the stocks of these relict fish species. Improving the technological processes of growing juvenile sturgeon fish, including the Caspian stellate sturgeon, the number of which has been rapidly decreasing in recent years, is one of the main tasks at present. We studied the conditions for growing stellate sturgeon larvae in the nursery ponds for artificial reproduction at different periods of their watering. It is known that the stocking of ponds with larvae that have switched to exogenous feeding occurs at the end of June or the beginning of July, this coincides with the time of maximum water heating in nursery ponds to extreme (26–28 °C) values and with a depletion of the food supply in them. Hydrobiological studies were carried out to assess the food supply in water bodies that were watered in the traditional (June 12–14) terms (control option) and earlier (May 28) 2 weeks earlier than usual (experimental option). In addition, the intensity of feeding and the growth rate of juvenile starred sturgeon in the indicated ponds was studied for 20–24 days. The results of the studies performed showed that the food supply in the experimental pond was higher, so the zooplankton was represented by four orders, the biomass on average ranged from 2,8 to 4,6 g/m³, and in the control variant, planktonic organisms were represented by three orders, total biomass from 0,3 to 2,5 g/m³. The same tendency can be traced for zoobenthos. The feeding intensity of stellate sturgeon fry reared in ponds of early watering had indicators in terms of the gastrointestinal tract filling index, fatness coefficient and growth rates higher than the juveniles kept in water bodies of traditional watering periods.

Potential applicability of a cyanobacterium as a biofertilizer and biopesticide in rice fields

This study aimed to evaluate the potential applicability of Anabaena variabilis SCAU30 as a biofertilizer and biopesticide in rice fields. The effects of A. variabilis SCAU30 inoculation on disease severity, plant growth, rice yield, and soil nutrients were investigated by microchamber, micro-area, and field experiments. The nitrogen fixation ability was estimated by acetylene reduction activity. Hormones were analyzed using liquid chromatography-tandem mass spectrometry. In microchamber experiments, the control efficacies of A. variabilis SCAU30 against rice sheath blight and bacterial blight were 62.3 ± 8.9% and 45.3 ± 5.6%, respectively. The cell extracts of A. variabilis SCAU30 exhibited high antagonistic effects on corresponding pathogens, whereas volatile compounds only showed inhibition on Xanthomonas oryzae. The results of pond experiments showed that inoculation with A. variabilis SCAU30 could promote the growth of rice plants, increase yield, control diseases, and decrease chemical nitrogen fertilizer input. Moreover, in field experiments, the combined treatment of A. variabilis SCAU30 and 50% topdressing fertilizer increased rice yields by 13.9%–22% compared with the conventional fertilizer treatment. This potentially represents economic gains of 26,753 ~ 38,987 Chinese Yuan ha−1 season−1 if sold as a green food. The present study suggests that A. variabilis SCAU30 may act as a fertilizer and pesticide in developing green rice in South China.

Review on Solar Ponds in Libya

Solar and renewable energies applications got a great interest and attention in the last few decades. Problems related to CO2 emissions, air pollution, Ozone layer depletion, global warming and environment issues raise the necessity for getting a clean and safe energy. For this purpose, the Center for Solar Energy Studies (CSERS) in Libya conducted a huge research work in different applications for solar and renewable energies. One of these important activities is the Solar Gradient Solar Pond technology. It is an effective solar energy collection and storage system which presents a relatively simple and economic method of providing low grade energy with the advantage of annual storage cycle.This paper presents a general review on researches and studies on solar ponds that were conducted by CSERS research team. Tajoura’s Experimental Solar Pond (TESP) is designed as an experimental facility enabling the investigation of various aspects of pond performance. It is constructed by the Center for Solar Energy Studies, in joint cooperation with a Swiss company, with a surface area of about 830 m2, and a depth of 2.5 m, coupled with an evaporative pond of 105 m2 area and 1.5 m deep, equipped with all necessary equipments and measuring control system.The paper also shows the experience of operating MSF desalination unit coupled with TESP solar pond. Finally, other factors affecting the solar pond’s thermal stability were also discussed.

БИОХИМИЧЕСКИЕ ПОКАЗАТЕЛИ СЫВОРОТКИ КРОВИ КРАСНУХОУСТОЙЧИВОЙ ПОРОДЫ КАРПА В КОНЦЕ НАГУЛЬНОГО ПЕРИОДА

Biochemical parameters of blood serum in resistant and susceptible to rubella pathogens groups of carp at the end of the feeding period are studied. The material was taken from 6 individuals of the Angelina scaly rubella-resistant breed kept at the experimental pond base "Sunoga" of the Papanin Institute for Biology of Inland Waters RAS, Yaroslavl oblast. For comparison, we used same-age carps from the fish farm "Kirya", Chuvash Republic, susceptible to rubella pathogens: 8 specimens of scaly and 8 mirror carps. Blood samples were taken from the caudal vein of the fish under study. The tube with blood was left at room temperature. After coagulation, the serum was taken with a fine needle syringe and transferred to an Eppendorf tube. Serum samples were frozen prior to testing. The analyzed individuals of the Angelina rubella-resistant breed differ from the scaly and mirror carp in high levels of total protein, albumins, glucose, urea, alkaline phosphatase, triglycerides, cholesterol and low levels of lipids and alanine aminotransferase. A comparative analysis with previously obtained data after wintering shows differences between the autumn and spring data. In the Angelina breed, the levels of most indicators significantly increase during the fattening period. The content of total protein increases several times, mainly due to globulins, glucose, urea, alkaline phosphatase, triglycerides. Thus, the metabolic processes aimed at the accumulation of proteins, stored lipids and carbohydrates increase in the organism of rubella-resistant carps. This is probably due to some specific characteristics of the Angelina breed, which allows the fish organism to successfully resist an infection with rubella pathogens in spring. The results of this study can be used in breeding for immunity resistance and for assessing the health status of fish in aquaculture.