A six-week trial was conducted to study the effects of different levels of organic carbon supplementation on biofloc color, structure and density, inorganic nitrogen and phosphorous dynamics, feed ...utilization and growth performance of Litopenaeus vannamei juveniles in an outdoor tank system under high-density and zero-exchange conditions. Organic carbon in the form of molasses was added daily to provide calculated carbon to nitrogen (C/N) ratios of 12:1 (CN-12), 15:1 (CN-15), and 18:1 (CN-18) based on the carbon–nitrogen content of the feed and the carbon content of the molasses during the entire experiment period No molasses was added in the control group which had a C/N ratio of 9 (CN-9). One additional treatment in which molasses supplementation was based on the actual level of total ammonia nitrogen (TAN) in the culture water (6g of carbon was added for each 1g of TAN as measured weekly), was also included and referred to as treatment CN-adjust. Juvenile shrimp (2.21±0.11g) were stocked into 20 experimental tanks filled with 500L of biofloc-rich water. Each treatment had four randomly assigned replicate tanks stocked at a density of 300shrimpm−3. Shrimp were fed a formulated feed with 36% crude protein and cultured for 6weeks. One week after the trial initiation, the color of suspended bioflocs began to differentiate, ranging from green to brown corresponding with the increase in C/N ratios. The higher C/N ratios shifted the predominately autotrophic biofloc to heterotrophic, simultaneously displaying higher levels of volatile suspended solids. The concentrations of TAN, nitrite-nitrogen, nitrate‐nitrogen, total inorganic nitrogen, and reactive phosphorus of all treatments fluctuated, showing a decline in total inorganic nitrogen concentration and an increase in reactive phosphorus concentration with the increase in C/N ratios. All five treatments exhibited survival rates above 95.5% with no significant differences between treatments. Better shrimp final weights and growth rates, with significantly higher yields and lower feed conversion ratio values were found for treatments CN-9, CN-adjust, and CN-12 than the CN-15 and CN-18 treatments. Three significant conclusions can be drawn from the results of this study: (1) VSS and turbidity values were superior quantifying parameters for quantitative determination of biofloc than SS or TSS in a biofloc-based system; (2) once a mature biofloc community is established, TAN and NO2−–N concentrations can be effectively controlled by either heterotrophic assimilation or autotrophic nitrification that helps maintain their concentrations at acceptable ranges for shrimp culture even at high stocking densities; and (3) the mixed type of biofloc dominated by both microalgae and autotrophic bacteria is more beneficial for shrimp performance in high density zero-exchange culture systems than systems dominated by heterotrophic bacteria, and also reduces production costs by reducing organic carbon input and oxygen use.
This paper provides useful info concerning the role of organic carbon supplementations in biofloc-dominated tank system operated with no water exchange and the changes in selected water quality indicators and performance of the Pacific white shrimp, Litopenaeus vannamei under these conditions.
•C/N ratio had effects on the culture of Litopenaeus vannamei in a biofloc-based system.•C/N ratio affected biofloc characteristics, and inorganic nitrogen and phosphorus dynamics.•High C/N ratio reduced growth and increased shrimp FCR.•Manipulating C/N input can serve as a useful management tool in biofloc-dominated systems.
Land-based seaweed ponds can produce 500–700 t of fresh weight (FW) ha
−1
year
−1
, but their profitability can be cut by the cost of pond construction, including ground leveling, infrastructure ...cost, and water agitation. A potentially cost-effective, land-based seaweed culture approach where seaweed grow on substrates by spray culture has been examined. We measured the yield and biomass quality of three intertidal cultivable seaweeds,
Ulva fasciata
,
Ulva compressa
, and
Hypnea musciformis
, in spray (known elsewhere also as film or drip culture) and pond culture approaches, varying surface inclination and nutrient loading. These technical details are necessary for the evaluation of the approach and for upscaling. The best yield (up to 84 g FW m
−2
day
−1
, 44–84% of yield in ponds) and quality (protein content and additional parameters) of spray-grown
U. fasciata
was obtained on 6°-inclined trays with highly fertilized water. The highest protein content (24.5%), but with reduced yield, was obtained on 80°-inclined trays.
H. musciformis
and
U. compressa
, apparently thanks to their stringy morphologies, yielded in spray culture up to 286 g FW m
−2
day
−1
and 172 g FW m
−2
day
−1
, respectively. The overall quality and resilience of spray-grown algae profited from nutrient enrichment, and the best yields were achieved with enrichment of 10 g N and 1 g P m
−2
day
−1
in
H. musciformis
and 15 g N and 1.5 g P m
−2
day
−1
in both
Ulva
species. Biomass growth occurred in layers, which visibly differed in color and consistency. A thin bleached top thalli layer protected the biomass below from dehydration and bleaching and allowed there a high photosynthetic rate. A spray culture of
Ulva
sp. on seawater-sprayed cement tiles, with minimal maintenance, yielded up to 50 g FW m
−2
of tile day
−1
. Economically, spray culture appears to be particularly suitable to the stringy algae.
►
Salicornia and
Sarcocornia leafy vegetable crops can be grown on full-strength seawater. ► Harvest schedule has a strong impact on the yield of
Salicornia and
Sarcocornia. ► Full-strength seawater ...improves the nutritional value of
Salicornia and
Sarcocornia leafy vegetables. ►
Salicornia and
Sarcocornia shoots contain high levels of omega-3 polyunsaturated fatty acids.
The halophyte
Salicornia was recently introduced as a fresh vegetable crop that thrives in extreme salt conditions. Two annual
Salicornia and two perennial
Sarcocornia ecotypes were investigated for yield production and nutritional value in response to different seawater concentrations in the irrigation solution. A harvest schedule based on a three-week cycle gave better productivity than a two-week or a four-week cycle. Total yield declined with increasing percentage of seawater above 50% in the irrigation water, however annual plants had always ca 2–3-fold higher fresh biomass in comparison to their perennial counterparts. Increased percentages of seawater in the irrigation solution had the following effects on ion concentrations in the shoots: no change in Ca
2+ and Mg
2+, a slight increase in K
+, and marked elevations in Na
+ and Cl
−. Importantly, total polyphenol, β-carotene and ureides, all known for their antioxidant capacities, rose with increasing seawater percentage, findings that indicated improved nutritional values for
Salicornia and
Sarcocornia irrigated with high concentrations of seawater. Impressively, both the annual
Salicornia and the perennial
Sarcocornia ecotypes exhibited high total shoot lipid contents of up to 2.41 and 2.06
mg
g
−1 fresh weight, respectively, which included an omega-3 fraction of 47.6 and 41.2% of the total fatty acid content. Moreover, the high fatty acid content of the annual
Salicornia ecotype was not significantly affected by increasing seawater concentrations. In this study, we thus demonstrated the feasibility of cultivating
Salicornia and
Sarcocornia by applying a multiple harvest system and 100% percentages of seawater in the irrigation water generating economic yields with high nutritional value. The findings also showed that
Salicornia and
Sarcocornia leafy vegetables may attract additional interest as an alternative source of omega-3 polyunsaturated fatty acids for human consumption, even when the crop irrigated solely with seawater.
•Litopenaeus vannamei PL were fed low (LP30) and high (HP40) protein diets in limited exchange nursery raceways.•Molasses prevented significant accumulation of NH3 but not NO2 in the culture ...medium.•The HP40 treatment had higher NO2, NO3 and PO4 than the LP30 treatment.•Shrimp fed HP40 had higher growth than those fed LP30, with no difference in survival or PER.•Lower protein feed may improve water quality, reduce feed cost and environmental impact.
The efficiency of shrimp production in limited exchange systems can be improved by optimizing the protein content of the feed. Therefore, a 62-d nursery study was conducted with 10-day-old Litopenaeus vannamei postlarvae stocked (5000PL10m−3) in four 40m3 raceways to evaluate the effect of high (40%) and low (30%) crude-protein (HP40 and LP30, respectively) diets and molasses supplementation on selected water quality indicators and shrimp performance under limited water exchange. Each raceway was equipped with a real-time dissolved oxygen monitoring system and a foam fractionator to control particulate matter. The level of molasses used in this study was effective in preventing significant ammonia accumulation in the culture medium. However, these supplementation levels were not effective in preventing nitrite accumulation. The HP40 treatment had significantly higher nitrite, nitrate and phosphate concentrations than the LP30 treatment. Shrimp mean final weight (0.94 vs. 1.03g) and specific growth rate (SGR) (11.03 vs. 11.19% day−1) were significantly different between treatments (P<0.05) LP30 and HP40, respectively, while mean survival (∼82% vs. 84%) and protein efficiency ratio (PER) (3.89 vs. 3.28) were not (P>0.05). The data suggest that substituting high-protein (40%) with low-protein (30%) feed in the nursery phase in a biofloc dominated system operated with minimal discharge may provide an alternative to improve shrimp biofloc technology, through improved water quality, cheaper (lower protein) feed and reduced environmental impact.
Superintensive shrimp culture in zero‐exchange, biofloc‐dominated production systems is more biosecure and sustainable than traditional shrimp farming practices. However, successful application of ...this technology depends upon optimizing dietary formulations, controlling Vibrio outbreaks, and managing accumulative changes in water quality and composition. A 49‐d study investigated the effect of two commercial feeds of differing protein content and an indoor limited‐exchange, biofloc‐dominated culture environment on Litopenaeus vannamei performance and tissue composition, water quality and ionic composition, and Vibrio dynamics. Juveniles (5.3 g) were stocked at 457/m3 into four 40 m3 shallow raceways containing biofloc‐dominated water and fed one of two commercial feeds with differing protein content, 35 or 40%. Shrimp performance, Vibrio populations, and changes in shrimp and culture water composition were monitored. There were no significant differences (P > 0.05) in shrimp performance (survival, weight, growth, specific growth rate, total biomass, yield, feed conversion ratio, and protein efficiency ratio) or proximate composition between feed types. The 40% protein feed resulted in higher culture water nitrate and phosphate concentrations, alkalinity consumption and bicarbonate use, and higher phytoplankton density. The presence of Vibrio, specifically Vibrio parahaemolyticus, reduced shrimp survival. This survival decrease corresponded with increased culture water Vibrio concentrations. Culture water K+ and Mg2+ increased significantly (P < 0.05), and Sr2+, Br−, and Cl− decreased significantly (P < 0.05) over time. While Cu2+ and Zn2+ did increase in shrimp tissue, no heavy metals accumulated to problematic levels in culture water or shrimp tissue. These results demonstrate the importance of monitoring Vibrio populations and ionic composition in limited‐exchange shrimp culture systems.
Increased environmental regulations and loss of crops due to viral disease outbreaks have created a demand for productive, pathogen-free, efficient and sustainable shrimp production practices. These ...methods, for the most part, call for raising shrimp under limited, minimal, water exchange with careful monitoring of water quality. Two studies were conducted using the Pacific white shrimp Litopenaeus vannamei to evaluate the effect of carbon supplementation on selected water quality indicators and shrimp performance in the nursery and the grow-out phases using the limited water discharge practice with molasses as carbon addition.
A preliminary nursery study was conducted in four 40m3 greenhouse-enclosed raceways stocked with 12-day old postlarvae at a density of 1800m−3 and were fed 45% crude protein feed. Molasses (24% carbon, w/w) was used for carbon supplementation to provide 6g of carbon for each 1g of total ammonia nitrogen (TAN) as measured in the water, and started 32 d after stocking, shortly after the TAN level has risen over 3mgL−1. The data suggest that molasses addition resulted in rapid reduction of TAN and nitrite-nitrogen and could be used to prevent buildup of these compounds.
The grow-out study was carried out using twenty 7.8m3 tanks stocked with juvenile shrimp at a density of 81m−3. Shrimp were fed a commercial diet (30% crude protein, Rangen Inc., Buhl, ID). Feed rations were determined based on assumed growth of 1gweek−1, FCR of 1.5 and weekly mortality rate of 0.5%. Molasses additions, at five levels, were started 26 days post stocking, to provide 0%, 50%, 100%, and 150% of the theoretical carbon level needed for bacteria to assimilate the TAN provided in the feed. The fifth treatment was based on the actual level of TAN in the tanks and was adjusted daily on as needed basis. The data suggest that under the condition of this study, addition of molasses did not result in a significant effect on water quality or on shrimp performance.
► Day length manipulations prevent flowering and allow year-round cultivation of the annual
Salicornia. ► Repetitive harvest prevents flowering and allows year-round cultivation of the perennial
...Sarcocornia. ► Light source gradient is a suitable tool to study day length effects on flowering. ► Short day flower induction is still evident in
Salicornia types growing during increasing day length. ► Seawater salinity does not affect the flowering pattern of Salicornieae.
Salicornia is a new vegetable crop that can be irrigated with highly saline water, even at salt concentrations equivalent to full-strength seawater. During leafy vegetable cultivation, the onset of the reproductive phase is an undesired phenomenon that reduces yield and quality and prevents year-round cultivation. Knowledge about the regulation of floral induction in the members of the tribe Salicornieae, however, is lacking. To establish year-round cultivation, we studied the flower induction of five
Salicornia and two
Sarcocornia varieties. Plants were grown under two day lengths, 13.5
h and 18
h, and harvested by a repetitive harvest regime. A 13.5-h day length prevented flower induction in the Israeli
Salicornia varieties, but a longer day length was required to prevent flower induction in two species originating from more northern latitudes. The onset of the reproductive phase under suboptimal short day length conditions severely reduced vegetative growth and yields in
Salicornia. In
Sarcocornia, the repetitive harvest regime prevented flowering, making it a promising candidate for year-round cultivation. Irrigating the plants with full-strength seawater (electrical conductivity 48
dS
m
−1) vs. water with moderate salinity (electrical conductivity 10
dS
m
−1) did not change the general flowering pattern of the studied Salicornieae members.
The considerable impact of disease outbreaks on commercial shrimp farming during the last two decades has significantly affected the operational management of shrimp farms worldwide. Crop losses ...forced shrimp producers to look for more sustainable culture practices and facility designs to minimize the risk associated with exposure to viral pathogens. Shrimp culture under limited discharge can increase biosecurity and minimize losses to disease outbreaks while reducing negative environmental impact. A 71-day nursery study was conducted in greenhouse-enclosed raceways to evaluate the effect of two water exchange regimes and the use of foam fractionators on selected water quality indicators, growth, survival, and health of Litopenaeus vannamei postlarvae (PL). Four 40m3 raceways were stocked with 4–5-day-old PL at a density of 4050PLm−3. All raceways were equipped with high pressure rapid sand filter, a pump, a center longitudinal partition over a 5.1cm PVC pipe with nozzles, eighteen 5.1cm airlift pumps, six 1m long air diffusers and a 5.1cm Venturi injector. Two out of the four raceways were each equipped with a home-made foam fractionator (FF). Average water usage in the two raceways operated with FF was 3.35%d−1 compared to the 9.37%d−1 used in the other two. Shrimp in the raceways operated with FF and the lower water exchange had greater mean final weight (1.91 and 2.0g vs. 1.73 and 1.43g), survival (100 and 92.4% vs. 55.9 and 81.8%), yield (7.64 and 6.89kgm−3 vs. 3.92 and 4.74kgm−3) and FCR (0.97 and 1.06 vs. 1.36 and 1.64) values than those operated without FF and with higher water exchange rate. Disease diagnostic results showed no signs of viral pathogen infection. Histological observations of samples collected at the study termination suggest that the shrimp raised in the higher water exchange raceways had greater external fouling and higher intestinal bacterial load than those maintained at lower water exchange. Nitrite–nitrogen was significantly lower in the reduced water exchange than the higher exchange raceways, whereas reactive phosphorus, turbidity, and algal density were significantly higher. No other differences in water quality were found between treatments. This study demonstrated the feasibility of producing healthy juveniles of the Pacific white shrimp under limited discharge conditions in tanks operated with foam fractionators with good growth, survival, yield and FCR results.
A 12-wk feeding trial was conducted with juvenile (0.6
±
0.3
g) Pacific white shrimp,
Litopenaeus vannamei, to evaluate the need for cholesterol supplements in plant based diets for shrimp reared in ...an outdoor system in the presence of natural foods. The basal diet was formulated with no fish meal and targeted crude protein levels of 35%. Five levels of supplemented cholesterol (0, 0.02, 0.04, 0.06, and 0.08%) resulted in diets analyzed to contain 0.061, 0.076, 0.110, 0.125, and 0.155% cholesterol. In addition, two levels of phytosterol supplements (0.05, 0.1%) were evaluated. Mean final weights and growth ranged from 19.13 to 20.20
g and 1.52 to 1.61
g/week, respectively. One-way ANOVA showed a significant difference (
P
≤
0.05) among shrimp fed diets containing the various levels of cholesterol, with diets containing ≤
0.076% total cholesterol producing smaller shrimp. No significant differences were detected among treatments with respect to survival, yields or FCR. Performance did not significantly improve when shrimp were offered diets supplemented with 0.06% (0.125% total cholesterol) or higher levels of cholesterol. This would suggest that the cholesterol requirement for
L. vannamei grow-out lies somewhere between 0.076 and 0.11%, however, a regression analysis predicted the cholesterol requirement for maximum growth to be 0.15% of the diet. Performance of shrimp fed the diets with two levels of phytosterol supplementation was compared to those fed the basal diet (no cholesterol supplementation) and the highest level of cholesterol (0.08%) supplementation. Mean final weight and growth rates were significantly different (
P
≤
0.05) with the mean final weights of the lowest phytosterol inclusion (0.05%) and the 0% cholesterol supplementation being similar, 19.03 and 19.13
g, respectively and the highest levels of phytosterol (0.1%) and cholesterol (0.08%) supplementation being similar, 20.18 and 20.20
g respectively. Likewise, the growth per week showed a similar trend, with the two lower levels of ingredient inclusion resulting in a growth rate of 1.52
g/week and the higher levels achieving a growth rate of 1.61
g/week. Survival, yield, and FCR were not significantly different between treatments.
The use of a co-extruded soybean poultry by-product meal with egg supplement was evaluated as a substitute for fish meal in a practical diet formulated to contain 32% crude protein and 8% lipid. The ...co-extruded product was substituted for menhaden fish meal on an iso-nitrogenous basis and offered to juvenile
Litopenaeus vannamei (mean initial weight±standard deviation, 1.13±0.06 g) over a 6-week period. Inclusion levels ranged from 0% (30 g fish meal/100 g diet) to 100% replacement (0 g fish meal/100 g diet). A fifth diet was formulated to contain no fish meal and 1 g krill meal/100 g diet. Furthermore, a commercial shrimp feed was included in the study to allow for a commercial reference. At the conclusion of the growth trial, survival, final weight, percent weight gain and feed efficiency (FE) were not significantly different among treatments. The inclusion of krill meal did not appear to improve attractability or palatability of the diet. Co-extruded soybean poultry by-product meal with egg supplement appears suitable as a substitute for fish meal in
L. vannamei diets.
