Outdoor Tanks Research Articles

Effects of solar ultraviolet radiation exposure on early ocean survival and fry-to-smolt growth of juvenile salmon

Marine survival rates of many juvenile salmon populations have declined in recent decades. Although several potential causes have been proposed, there has been little conclusive evidence for which factors are responsible or not responsible for these declines. We experimen- tally addressed the hypothesis that exposure of coho salmon Oncorhynchus kisutch or sockeye salmon O. nerka to solar ultraviolet-B radiation (UVB) during freshwater rearing of fry and parr life-history stages increases mortality at the time of smoltification and ocean entry. Juvenile coho and sockeye salmon were reared in outdoor hatchery tanks either exposed to full spectrum sun- light or shielded from UVB radiation by plastic screens for up to 9 mo prior to release. Smolts were tagged with acoustic transmitters and detected with hydrophone receivers during their downriver and early ocean migration. Survival of treatment groups was compared using Cormack-Jolly- Seber and Burnham mark-recapture models. While exposure to UVB resulted in decreased growth of juvenile coho salmon, survivorship during the early marine period was unaffected by the UVB treatment for both populations. This first attempt to experimentally address the hypo - thesis of impaired survival resulting from solar UVB radiation has shown that other factors are more likely responsible for observed declines in salmon marine survival rates.

Thicker host tissues moderate light stress in a cnidarian endosymbiont

The susceptibility of algal-cnidarian holobionts to environmental stress is dependent on attributes of both host and symbiont, but the role of the host is often unclear. We examined the influence of the host on symbiont light stress, comparing the photophysiology of the chlorophyte symbiont Elliptochloris marina in two species of sea anemones in the genus Anthopleura. After 3 months of acclimation in outdoor tanks, polyp photoprotective contraction behavior was similar between the two host species, but photochemical efficiency was 1.5 times higher in A. xanthogrammica than in A. elegantissima. Maximum relative electron transport rates, derived from rapid light curves, were 1.5 times higher in A. xanthogrammica than in A. elegantissima when symbionts were inside intact tissues, but were not significantly different between host species upon removal of outer (epidermis and mesoglea) tissue layers from symbiont-containing gastrodermal cells. Tissues of A. xanthogrammica were 1.8 times thicker than those of A. elegantissima, with outer tissue layers attenuating 1.6 times more light. We found no significant differences in light absorption properties per unit volume of tissue, confirming the direct effect of tissue thickness on light attenuation. The thicker tissues of A. xanthogrammica thus provide a favorable environment for E. marina - a relatively stress-susceptible symbiont - and may explain its higher prevalence and expanded range in A. xanthogrammica along the Pacific coast of North America. Our findings also support a photoprotective role for thicker host tissues in reef corals that has long been thought to influence variability in bleaching susceptibility among coral taxa.

Transcriptome analysis of Saccharomyces cerevisiae at the late stage of very high gravity (VHG) fermentation

The effect of culture system on growth and economics performance of Orechromis niloticus (Nile tilapia) in concrete tanks was investigated. Four outdoor concrete tanks measuring 2.5 x 2 m was used for the study for 24 weeks culture period. The culture systems included the use of algae only at the stocking rates of 4 fishes/m2 (T1), algae plus commercial feed at the stocking rate of 10 fishes/m2 (T2), and commercial feed only at the stocking rate of 20 fishes/m2 (T3). The tanks were stocked with O. niloticusfingerlings with mean weight of 1.160, 1.030 and 0.255 g for T1, T2 and T3, respectively. Each treatment was replicated twice. Data collected were analyzed using analysis of variance and mean comparison was carried out using Duncan Multiple Range Test (DMRT). All tests were carried out at 5% probability level. The result on growth performance show that the intensive system (T1) was significantly different in some growth parameters (P < 0.05) such as yield (0.115, 0.830 and 1.260 kg/m3 for T1, T2 and T3, respectively), specific growth (1.975, 2.750 and 3.425% for T1, T2 and T3, respectively), survival rate (90, 80 and 91% for T1, T2 and T3, respectively), and feed conversion ratio (1.150 and1.030 for T2 and T3, respectively). Economically, the intensive system was more profitable with a gross margin of N 122, which was 40% more profitable than the extensive system (T1 with Gross margin of N80), and 269% than commercial feed plus algae (T2 with Gross margin of – N 194). The cost of production (incidence of cost) showed that it cost more (N 447) to produce O. niloticus using commercial feed plus algae (T2 ) in concrete tank than the use of algae only (T1) (N 268) and the use of commercial feed only (T3) (N380). Key words: Culture system, growth performance, economic performance,Oreochromic niloticus.

Performance of catfish (Clarias gariepinus, Burchell, 1822) fed enzyme supplemented dried rumen digesta

The growth response of catfish (Clarias gariepinus) fingerlings fed with varying levels of enzyme supplemented dried rumen digesta meal (EDRD) was conducted for 70 days in Nursery cages (hapa nets) suspended in outdoor concrete tanks. One hundred and fifty (150) fish were randomly assigned to five diets formulated such that EDRD replaces soybean at 0, 10, 20, 30, and 40%, respectively. Thirty fish were assigned to each of the diets in hapa nets and fed at 5% body weight daily. Evaluation of growth parameters and nutrient utilization of fish followed standard methods and were based on feed intake, weight gain, feed conversion ratio, specific growth rate and protein efficiency ratio. Result showed that control (0%) diet gave highest weight gain of 54.25 g followed by 10, 20, 30%, while the least weight gain was obtained from 40% dietary treatment which recorded a value of 36.09 g. This experiment revealed that EDRD can be tolerated by C. gariepinus fingerlings and support growth at 40% with little effect on specific growth rate (SGR) and feed conversion ratio (FCR) (p<0.05). There was no mortality encountered during the experimental period. Key words: Catfish (Clarias gariepinus), enzyme supplemented dried rumen digesta meal (EDRD), fish, shellfish.

Effects of Shading on the Reproductive Output and Embryo Viability of Gulf Killifish

AbstractGulf killifish Fundulus grandis broodstock (7.3 ± 0.2 g [mean ± SE]) were held in static outdoor tanks at a 4:1 (female : male) sex ratio and a density of 20 fish/m3. Shade cloth was used to cover 0, 40, or 80% of the surface area of 12 randomly selected outdoor tanks. Eggs were collected from all tanks twice per week by using spawning mats suspended 15 cm below the water surface. Collected eggs were measured volumetrically and assessed for total number and embryo viability. The use of shade cloth had a significant effect on water temperature, the number of eggs collected, and embryo viability. Specifically, shading affected mean weekly water temperature, and the 80% treatment had significantly lower temperatures than both the 0% and 40% treatments during the months of June through August and than the 0% treatment in September. There was a clear cyclical reproductive pattern across all treatments, in which peaks in egg production occurred between the full and new moon phases for the majority of collection dates. Significant differences in the mean number of eggs collected among shade cloth treatments were present only for the month of September, when the 80% treatment produced significantly fewer eggs. The proportion of viable embryos was significantly higher for the 80% treatment than for the other treatments for the months of June, July, and August. The use of shade cloth during the summer months can increase the number of viable embryos produced during the summer depression of the protracted, bimodal spawning season of cultured Gulf killifish.

Impact of surface conditions on thin sea ice concentration estimate from passive microwave observations

Ice concentration retrieved from spaceborne passive microwave observations is a prime input to operational sea ice monitoring programs, numerical weather prediction and global climate models. However, it is usually underestimated by existing algorithms due to surface conditions, especially in case of young ice types. Evaluation of those algorithms identifies errors in concentration estimates but does not necessarily link them to the adverse surface conditions. The present study is an attempt to establish those links for young ice (<25cm) thick. It uses measurements of microwave emission from artificially grown sea ice in an outdoor tank and calculates ice concentration using five established algorithms: NT, Bootstrap (BSA), NT2, ASI and ECICE. Since the actual concentration is known (100%), then any deviation from this value is considered an error and can be linked to the observed surface conditions, which are usually caused by weather events. Those conditions were acquired on hourly or daily basis. Results identify key conditions that lead to underestimation of ice concentration. They include surface refreezing, slush, snow settling following fresh snowfall, and falling precipitation in different forms. The study shows also that NT and NT2 are most affected by surface processes while BSA performs better. ASI is much less affected because it uses the high frequency channel (e.g. SSM/I 85GHz), which is sensitive only to processes within the top snow layer. ECICE, with its probabilistic and ensemble approach shows also good results under most surface conditions. Dry or wet snow does not lead to significant difference in ice concentration estimate. The study also aims at validation of ECICE.

Methanoculleus spp. as a biomarker of methanogenic activity in swine manure storage tanks

Greenhouse gas emissions represent a major problem associated with manure management in the livestock industry. A prerequisite to mitigate methane emissions occurring during manure storage is a clearer understanding of how the microbial consortia involved in methanogenesis function. Here, we have examined manure stored in outdoor tanks from two different farms, at different locations and depths. Physico-chemical and microbiological characterization of these samples indicated differences between each tank, as well as differences within each tank dependent on the depth of sampling. The dynamics of both the bacterial and archaeal communities within these samples were monitored over a 150-day period of anaerobic incubation to identify and track emerging microorganisms, which may be temporally important in the methanogenesis process. Analyses based on DNA fingerprinting of microbial communities identified trends common among all samples as well as trends specific to certain samples. All archaeal communities became enriched with Methanoculleus spp. over time, indicating that the hydrogenotrophic pathway of methanogenesis predominated. Although the emerging species differed in samples obtained from shallow depths compared to deep samples, the temporal enrichment of Methanoculleus suggests that this genus may represent a relevant indicator of methanogenic activity in swine manure storage tanks.

The effects of herbivore exclusion and nutrient enrichment on growth and reproduction of Halimeda macroloba

The questions on how Halimeda macroloba allocates resources to growth and sexual reproduction when encountering herbivores and elevated nutrient concentrations were experimentally examined in the natural subtidal zone and in water tanks. The field experimental design comprised 96 plots (50 50 cm 2 ), with and without herbivores, and two nutrient levels. Cages were used to exclude fish herbivores: uncaged plots and fully caged plots; and 2 nutrient levels were manipulated: enriched and ambient levels in order to determine the effect of nutrients. Osmocote slow-release fertilizer was placed in each enriched plot. For the outdoor water tank experiments, mechanical clipping was used to simulate grazing on algae. Nutrient enrichment had a positive effect on the growth and reproduction of H. macroloba both in the field and water tank experiments, and herbivory or simulation of grazing did have a significant effect on the growth of algae in the water tank experiments. H. macroloba produced gametangia within 1-2 weeks after nutrient enrichment, to indicate that enrichment might be the trigger for reproduction of H. macroloba. From the tissue nutrient levels, the C:N, C:P, and N:P (18.9, 639, and 33.7) ratios indicated that the productivity of H. macroloba was phosphorus limited.

Sediment tolerance of Sargassum algae inhabiting sediment-covered rocky reefs

Although sediment deposition has detrimental effects on macroalgal settlement and recruitment, fucoid algae (mainly Sargassum duplicatum) thrive on rocky reefs always overlaid with fine sediments in sheltered sites of Kagoshima, Japan. The aim of the present study was to assess their ability to settle and recruit onto sediment-covered substrata. A transplant experiment using boulders with Sargassum juveniles attached showed that the 30-day survival rate was as high as 50% even for the juvenile stage (<10 mm) on boulders completely buried with sediment. In addition, an outdoor tank experiment testing the effects of different sediment thicknesses (0–4 mm) on already settled 4-day old S. duplicatum germlings indicated significant reductions in growth by the presence of sediment cover even at 0.5 mm but no significant increase in mortality up to 2 mm. Furthermore, an in situ experiment in which sterilized cobbles were placed at a sediment-covered site to allow sediment to settle over them before the embryo release showed a uniformly high recruitment of Sargassum over the cobbles. This suggests the presence of unknown mechanisms to allow the settlement of propagules on substrata thinly but completely covered by fine sediments.

The Phytoplankton Nannochloropsis oculata Enhances the Ability of Roseobacter Clade Bacteria to Inhibit the Growth of Fish Pathogen Vibrio anguillarum

BackgroundPhytoplankton cultures are widely used in aquaculture for a variety of applications, especially as feed for fish larvae. Phytoplankton cultures are usually grown in outdoor tanks using natural seawater and contain probiotic or potentially pathogenic bacteria. Some Roseobacter clade isolates suppress growth of the fish pathogen Vibrio anguillarum. However, most published information concerns interactions between probiotic and pathogenic bacteria, and little information is available regarding the importance of phytoplankton in these interactions. The objectives of this study, therefore, were to identify probiotic Roseobacter clade members in phytoplankton cultures used for rearing fish larvae and to investigate their inhibitory activity towards bacterial fish pathogens in the presence of the phytoplankton Nannochloropsis oculata.Methodology/Principal FindingsThe fish pathogen V. anguillarum, was challenged with 6 Roseobacter clade isolates (Sulfitobacter sp. (2 strains), Thalassobius sp., Stappia sp., Rhodobacter sp., and Antarctobacter sp.) from phytoplankton cultures under 3 different nutritional conditions. In an organic nutrient-rich medium (VNSS), 6 Roseobacter clade isolates, as well as V. anguillarum, grew well (109 CFU/ml), even when cocultured. In contrast, in a phytoplankton culture medium (ESM) based on artificial seawater, coculture with the 6 isolates decreased the viability of V. anguillarum by approximately more than 10-fold. Excreted substances in media conditioned by growth of the phytoplankton N. oculata (NCF medium) resulted in the complete eradication of V. anguillarum when cocultured with the roseobacters. Autoclaved NCF had the same inhibitory effect. Furthermore, Sulfitobacter sp. much more efficiently incorporated 14C- photosynthetic metabolites (14C-EPM) excreted by N. oculata than did V. anguillarum.Conclusion/SignificanceCocultures of a phytoplankton species and Roseobacter clade members exhibited a greater antibacterial effect against an important fish pathogen (V. anguillarum) than roseobacters alone. Thus, cooperation of N. oculata, and perhaps other phytoplankton species, with certain roseobacters might provide a powerful tool for eliminating fish pathogens from fish-rearing tanks.

Nitrate uptake and duration of internal nitrogen reserves in the kelp Eisenia arborea

Abstract Eisenia arborea is the kelp species that is distributed furthest south in the northern hemisphere. Although much is known about how the giant kelp, Macrocystis pyrifera, responds to nutrient-poor conditions, very little is known about Eisenia, even though these two kelps share much of their habitat. The response of E. arborea to environmental nitrogen shortage was explored by determining short-term nitrogen uptake in the laboratory, duration of internal nitrogen reserves in nutrient-poor tanks, and recovery of reserves during weekly pulse fertilization with nitrate. Nitrate uptake was linear for at least 3 h at all concentrations and did not exhaust nitrate in the media. In both experiments in nutrient-poor outdoor tank cultures, regardless of initial tissue nitrogen concentrations, tank nitrate fell to undetectable levels after 4 weeks, and internal tissue nitrogen reserves fell to 1.0% of dry weight within 5 weeks. Low internal reserves were replenished in fertilized treatments, which had significantly greater dry weight tissue nitrogen (up to 1.3%) than thalli in non-fertilized tanks, in which algae tissue nitrogen fell to and remained constant at 1%. We conclude that the nitrogen physiology of E. arborea is adapted to survive a maximum of 5 weeks in the field under nutrient-poor conditions, similar to the giant kelp M. pyrifera.

Highly virulent Photobacterium damselae subsp. piscicida isolated from Taiwan paradise fish, Macropodus opercularis (L.), in Taiwan

In Taiwan, a fish conservation farm had about 6,250 Taiwan paradise fishes, Macropodus opercularis (L.), which were separately cultivated in an outdoor tank containing 3,250 fishes, and an indoor tank containing the rest. The water supplying both tanks was the same running water source from the adjacent hills. Following a change in the fish feed (the commercial aquaculture feed became eel’s feed) to all fishes in May 2010, rotten body surfaces were only found in diseased and dead fishes in the outdoor tank. Interestingly, no sick fishes were found in the indoor tank. The clinical findings of the diseased fishes were bleeding at basal fins, peripheral site of genital pore, and bilateral surface of the abdomen. Additionally, we discovered whitish-mucus gills, edema of the intestines, and multi-focal white tubercles in infected fishes during gross examination. The results of the histopathology study showed that there were numerous multi-focal granulomas in the spleen, posterior kidney, and liver. Furthermore, Photobacterium damselae subsp. piscicida was isolated from lesions of the ailing fishes. We conducted an experimental animal virulence test, and our data revealed that P. damselae subsp.piscicida was a highly virulent pathogen. Fortunately, P. damselae subsp. piscicidaappeared to be susceptible to most commonly used antimicrobial agents, according to the results of the antibiotic sensitivity study. We recommended a treatment with oxolinic acid (20 mg/kg/day) in the feed for 7 days for all Taiwan paradise fishes. The fishes’ condition significantly improved and the disease appeared to be controlled. Key words: Conservation, photobacteriosis, Taiwan paradise fish, virulence.

The effect of combining shading and continuous lighting on the suppression of sexual maturation in outdoor-reared Atlantic cod, Gadus morhua

Sexual maturation of Atlantic cod, Gadus morhua, is a major problem during commercial on growing as fish divert energy away from growth into gonadal development. While the photoperiod regimes that inhibit maturation are well described, when manipulations are applied in a commercial cage setting, using standard lighting technology, maturation is not completely inhibited. This has led to the hypothesis that the enhanced light sensitivity of cod allows it to perceive ambient illumination over the artificial lighting. A 13 month trial was conducted to determine the effectiveness of net shading ambient photoperiod in addition to constant lighting to suppress maturation of cod in outdoor conditions. By reducing the relative difference between day and night light intensities, it was hypothesised that maturation in cod could be inhibited as fish could not perceive, and thus use the ‘ambient daylength’ signal to entrain their reproductive cycle. Two outdoor tanks were covered in either a low density (70% reduction in ambient illumination) or a high density (90% reduction in ambient illumination) shade netting and then illuminated continuously by cathode lighting. These were compared to two indoor tanks in which ambient light was excluded and instead they were illuminated by similar lighting running either under a simulated natural photoperiod or continuous illumination. The work demonstrated that the shade netting could improve the relative performance of the artificial lighting outdoors from < 2% in a non-shaded system to 6.6% (low shade treatment) and 31.3% (high shade treatment) of the day light intensity. Importantly, both shading treatments were effective at suppressing sexual development as confirmed through histology and reduced GSI (female mean ≤ 2.18%, male mean ≤ 1.39%), oocyte diameter (mean < 400 μm) and sex steroid profiles (female 17β-estradiol mean ≤ 0.24 ng.ml − 1 , male 11-ketotestosterone mean ≤ 3.35 ng.ml − 1 ) as well as enhanced growth. These results are a promising demonstration of the potential value of shading systems to enhance the efficacy of photoperiod control.

Use of soy protein concentrate in practical diets for Pacific white shrimp (Litopenaeus vannamei) reared under field conditions

The objective of this study was to evaluate the production response of Litopenaeus vannamei fed with production diets containing increasing percentages (0, 4, 8, and 12%) of soy protein concentrate (SPC). The diets were commercially produced and evaluated in outdoor tanks and 0.1-ha production ponds. In the outdoor green water tank system, the four test diets and a commercial reference diets were offered to juvenile shrimp (1.0 g initial weight) reared over a 10-week period at a stocking density of 30 shrimp per tank. At the conclusion of the tank trial, there were differences in final weight (13.5–15.0) biomass (399 g–432 g), and FCR (1.17–1.28) with the reference diet generally producing significantly better results than the test diets albeit there were no significant differences among the SPC test diets. In addition, the test diets were evaluated in 0.1-ha ponds using four replicates per diet. Nursed juvenile shrimps (0.013 g initial weight) were stocked at 35 shrimp m−2 and were cultured under standardized pond production conditions for 18 weeks. At the conclusions, net yield (4,190–5,051 kg/ha), final mean weight (13.5–15.7 g), survival (86.7–93.3%), and FCR (1.3–1.59) were evaluated with no significant differences between dietary treatments. The results from this study demonstrated that SPC inclusion up to 12% SPC in soybean-based diet can be used in commercial feed formulations for L. vannamei without causing negative effect on growth, feed conversion, survival and net yield.

Diurnal courses of net photosynthesis and photosystem II quantum efficiency of submerged Lagarosiphon major under natural light conditions

An optode device for net-photosynthesis measurements, based on oxygen-depending quenching of fluorescence from O2-specific sensors, and PAM fluorometry have been used to study diurnal courses of net-photosynthesis and the Fv/Fm ratio of the submerged plant Lagarosiphon major. Plants were pre-cultivated and studied in large mesocosm flow-through outdoor tanks under 50% and 80% shade cloth, respectively. Growth under the different shade cloths resulted in similar light compensation points (∼20μmol photonsm−2s−1), but strongly different light saturation levels, with about 150μmolm−2s−1 for plants grown under 80% shade cloth and about 350μmolm−2s−1 for plants grown under 50% shade cloth. Plants under both growth conditions showed a transient reduction of the maximum Fv/Fm value in the afternoon (down to 70% of the morning control values under 80% shade cloth and down to 85% under 50% shade cloth), which was not accompanied by a reduction of the net photosynthetic rate. This indicated that the fluorescence parameter Fv/Fm must not be a reliable indicator of the rate of photosynthesis under all conditions. The new photo-optical device became evidenced as a valuable tool not only for laboratory experiments, but also for field studies of gas exchange of submerged plants.

Can biotic resistance be utilized to reduce establishment rates of non-indigenous species in constructed waters?

Understanding the mechanisms that facilitate establishment of non-indigenous species is imperative for devising techniques to reduce invasion rates. Passively dispersing non-indigenous organisms, including zooplankton, seemingly invade constructed waters (e.g., ornamental ponds, dams and reservoirs) at faster rates than natural lakes. A common attribute of these invaded water bodies is their relatively young age, leading to the assertion that low biotic resistance may lead to their higher vulnerability. Our aim was to determine if seeding of young water bodies with sediments containing diapausing stages of native zooplankton could accelerate community development, leading to greater biotic resistance to the establishment of new species. Twenty outdoor tanks were filled with water (1,400 L) and nutrients added to attain eutrophic conditions. Ten treatment tanks had sediments added, sourced from local water bodies. In the remaining ten, sediments were autoclaved, and received zooplankton via natural dispersal only. In an initial 12 month monitoring period, species richness increased at a greater rate in the treatment tanks (at 12 months average standing richness per tank = 3.8, accumulated richness = 8.2) than control tanks (2.6 and 5.0, P < 0.05). Treatment tanks developed assemblages with greater proportions of species adapted to pelagic conditions, such as planktonic cladocerans and copepods, while control tanks generally comprised of smaller, littoral dwelling, rotifers. Analysis of similarities indicated community composition differed between the control and treatment groups at 12 months (P < 0.01). Two copepod, four rotifer and one cladoceran species were intentionally added to tanks at 12 months. In the 3 month post-introduction period, five of these species established populations in the control tanks, while only two species established in the treatment tanks. The calanoid copepod Skistodiaptomus pallidus, for example, a non-indigenous species confined to constructed waters in New Zealand, established exclusively in tanks where native calanoid copepod species were absent (primarily control tanks). Our study suggests that biotic resistance could play an important role in reducing the establishment rate of non-indigenous zooplankton. It also provides evidence that seeding constructed water bodies with sediments containing diapausing eggs of native species may provide an effective management tool to reduce establishment rates of non-indigenous zooplankton.

Pond production of Pacific white shrimp ( Litopenaeus vannamei) fed high levels of soybean meal in various combinations

The objective of this study was to demonstrate the feasibility of four diets formulated to contain high levels of soybean meal in combination with either poultry by-product, fish meal, distiller's dried grains with solubles, or pea meal in production diets for L. vannamei. Outdoor ponds and tanks were utilized to evaluate the response of the shrimp over the culture period. The pond production trial was conducted in 0.1-ha ponds stocked with juvenile shrimps (mean weight ± S.D., 0.038 ± 0.004 g) at 35 shrimp m −2 and cultured under standardized pond production conditions for 18 weeks. The same dietary treatments plus a commercial reference diet were offered to shrimp (initial weight of 2.1 g) maintained in outdoor tanks (800 L) over a 12-week period. The results for the pond study demonstrated that final production ranged between 5054 and 5265 kg ha −1, mean final weight varied from 15.98 to 16.28 g, survival ranging from 86.6 to 93.7%, and FCR was between 1.32 and 1.37. There were no differences (P ≥ 0.05) or notable trends in shrimp production variables among different test diets. Shrimp reared in the outdoor tanks confirmed these findings. Average final weights ranged between 18.53 and 19.00 g, survival varied from 97.3 to 98.7%, and FCR was between 1.30 and 1.33. The results from the outdoor tank study also showed no differences (P ≥ 0.05) in final weight, survival, or FCR among test diets. Diet containing partial fishmeal showed no benefit on growth performance of L. vannamei comparing with diets containing high levels of soybean meal in combinations with poultry by-product, distiller's dried grains with solubles or pea meal. Therefore, these studies demonstrated that practical shrimp feeds containing no fish meal had no negative impact on growth performances of L. vannamei.

Growth Response of &lt;I&gt;Catla Catla&lt;/I&gt; (Actinopterygii: Cypriniformes: Cyprinidae) to Soya and Maize Supplemented Traditional Feed Mixture

Background. In Indian carp culture, a 1 : 1 mixture of rice bran and oil cake is traditionally used as feed in powder form; it is nutritionally inadequate and also a large part of it goes unutilized as the fish cannot feed on the powder effectively. With a view to improve its nutritional quality and reduce the wastage, the mixture was supplemented with soya and maize flours and converted into pellet form. The performance of the supplemented diets was evaluated by feeding them to catla, Catla catla, one of the popular Indian major carps. Materials and methods. Two test diets were formulated supplementing the feed mixture with soya flour (10% and 20%) and maize flour (39%), replacing equal quantities of rice bran and oilcake. These diets along with the control diet were fed to triplicate groups of catla fry maintained in outdoor cement tanks for 120 days. Results. The test diets enhanced growth and net fish production significantly (P &lt; 0.05). This resulted in higher economic returns under the two test treatments. Survival of fish ranged from 74% to 76%.&nbsp; Carcass of fish receiving the test diets had significantly (P &lt; 0.05) higher lipid and lower moisture levels. Digestive enzyme activity was affected positively (P &lt; 0.05) by the test diets. Conclusion. Replacing rice bran and oilcake from the traditional feed mixture with soya and maize flours proved economically viable.

Effects of stocking density on the performance of Pacific white shrimp Litopenaeus vannamei cultured under pond and outdoor tank conditions using a high soybean meal diet

The objective of this study was to evaluate the effect of stocking density on the growth performance and economic feasibility for the culture of Litopenaeus vannamei fed plant based diets and cultured in production ponds and an outdoor tank system. Juvenile shrimps (0.015 g initial weight) were stocked in sixteen 0.1 ha ponds with stocking densities of 17, 26, 35, and 45 shrimp m − 2 and cultured under standardized pond production conditions for 16 weeks. Daily feed rates were predetermined using expected growth per week of 1.3 g, a feed conversion ratio (FCR) of 1.2, and an estimated survival rate of 78%. Additionally, juvenile L. vannamei (2.8 g initial weight) were stocked into 24,800-L tanks at the densities of 15, 25, 35, 45, 55, and 65 shrimp m − 2 with 4 replicates per treatment and cultured for 10 weeks. Daily feed inputs were calculated based upon an expected weekly weight gain of 1.3 g and an expected FCR of 1.2. At the conclusion of the trials, final production, final mean weight, FCR, size distribution and survival were determined. The results for the pond study demonstrated that there was a trend of negative correlation between stocking density and growth. Mean final weight (± SD) of shrimp across treatments ranged from 20.70 to 25.25 g. Survival ranged from 58.0 to 65.1%, and FCR was between 1.17 and 1.54. These differences were not significant (P ≥ 0.10) among treatments, however, higher stocking density resulted in significantly greater yield. Final production was between 2660 and 6149 kg ha − 1 . There were no significant differences in partial returns among different densities for the pond study. The results for the outdoor tanks showed that shrimp growth were inversely related to stocking density, with mean final weight ranged from 13.42 to 16.13 g. Final biomass ranged between 286.15 and 637.20 g tank − 1 . There was a negative correlation between stocking density and FCR with FCR ranging from 1.15 to 1.54. Survival ranged from 93.4 ± 5.6 to 100.0 ± 0.0%, however, there was no significant effect of stocking density on survival rate. Additionally, there were no significant differences in production value and partial income data among treatments under pond production study.

Bioreactors in out-door plastic tanks: the effects of microbial protein on the growth, feed utilization and haematology in Oreochromis niloticus (linnaeus) fingerlings

Bioreactors in out-door plastic tanks: the effects of microbial protein on the growth, feed utilization and haematology in Oreochromis niloticus (linnaeus) fingerlings