Nursery of young Litopenaeus vannamei _2017

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Aquacultural Engineering 78 (2017) 140–145

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Nursery of young Litopenaeus vannamei post-larvae reared in biofloc- and microalgae-based systems

MARK

⁎

Rodrigo Schveitzera, , Marco Antonio de Lorenzob, Felipe do Nascimento Vieirab, Scheila Anelise Pereirab, José Luiz Pedreira Mouriñob, Walter Quadros Seiffertb, Edemar Roberto Andreattab a b

Federal University of São Paulo, Department of Marine Sciences, Santos, SP, Brazil Federal University of Santa Catarina, Department of Aquaculture, Marine Shrimp Laboratory, Florianópolis, SC, Brazil

A R T I C L E I N F O

A B S T R A C T

Keywords: Shrimp BFT Autotrophic Total suspended solids

A 13-day nursery trial was conducted to evaluate the performance of young Litopenaeus vannamei post-larvae (from PL6 to PL18) reared in both biofloc and microalgae-based systems at a stocking density of 67 PLs L−1. The effects of different concentrations of total suspended solids (TSS) on PL performance were also evaluated. One experimental group was reared in a conventional microalgae-based system with daily water exchange and daily addition of microalgae (herein called microalgae treatment). The other two experimental groups were reared using biofloc technology (BFT) with daily dextrose addition and no water exchange, but in the “Biofloc-500” treatment, TSS were maintained at around 500 mg L−1, while in the “Biofloc-700” treatment, TSS were maintained at around 700 mg L−1. Water quality variables remained within the appropriate range for larval culture. In microalgae treatment, ammonia control was likely associated with its assimilation into microalgae biomass and daily water exchange. In biofloc tanks, however, the addition of dextrose stimulated the production of bacterial biomass from ammonia. This system required only 12.9% of the water used by the microalgae treatment since water was not exchanged during the culture. The nursery of young PLs resulted in similar (P > 0.05) performance in all treatments: survival > 94%, PL length ∼ 11.5 mm, and PL dry weight ∼ 1.2 mg. In addition, the salinity stress test (> 90.0%) was not significantly different among treatments. Our results indicate that BFT can be as effective as the microalgae-based system for the nursery of young L. vannamei post-larvae. We also found that post-larvae performance was similar (P > 0.05) between biofloc treatments, indicating that organisms can tolerate environments with large quantities of solids.

1. Introduction A nursery system can be defined as the intermediate step between the early post-larval (PL) stage and the grow-out phase in shrimp culture (Mishra et al., 2008). Strategies for this phase involve holding postlarvae at very high densities in small tanks for 15 − 60 days with precise technical management, feeding and water quality monitoring (Jory and Cabrera, 2012; Samocha, 2010). In some countries, e.g., Brazil and Ecuador, intensive nursery (∼ 60 PLs L−1) of short duration has been used to produce 20- or 25-day-old PLs in a two-phase production system (Rocha et al., 2003; Samocha, 2010). Water management in nursery systems is variable (see review by Samocha, 2010). Nevertheless, a controversial practice associated with nursery systems is the high daily water exchange used during culture to

maintain adequate water quality (Samocha et al., 2003). In the last few years, however, crop losses have forced shrimp farmers to look for more biosecure culture practices, such as zero water exchange, to minimize the risks associated with exposure to pathogens (Browdy et al., 2001). An alternative approach to avoid high rates of water exchange in rearing shrimp larvae relies on biofiltration and water reuse (Juarez et al., 2010). However, this approach can be problematic because the duration of larval rearing is short relative to the time needed to establish a mature biological filter. Therefore, biofloc technology (BFT) can be an interesting option to rear young post-larvae in short duration nursery. Heterotrophic bacteria, which are present in bioflocs and involved in ammonia control, have a growth rate greater than that of nitrifying bacteria (Metcalf and Eddy, 1991) that are present in biological filters.

⁎ Corresponding author at: Universidade Federal de São Paulo (UNIFESP), Departamento de Ciências do Mar, Edifício Acadêmico II, Rua Dr. Carvalho de Mendonça, 144, Encruzilhada, Santos, SP, CEP 11070-100, Brazil. E-mail address: [email protected] (R. Schveitzer).

http://dx.doi.org/10.1016/j.aquaeng.2017.07.001 Received 4 November 2016; Received in revised form 30 June 2017; Accepted 2 July 2017 Available online 08 July 2017 0144-8609/ © 2017 Elsevier B.V. All rights reserved.

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2.2. Experimental conditions

BFT is a production system whereby dense microbial communities are managed to control ammonia mainly released by the reared organisms. Ammonia can be assimilated by microalgae or heterotrophic bacteria, or it can be oxidized by nitrifying bacteria (Ebeling et al., 2006). These organisms usually grow in the form of microbial flocs (bioflocs) that can be used as natural food for the cultivated species (De Schryver et al., 2008). The main characteristics of this system are high stocking densities, heavy mixing, intense aeration, low, to no, water exchange, and high organic matter input (Browdy et al., 2001). Although BFT has its advantages, a serious problem can arise when biofloc systems are used to culture young post-larvae. Specifically, a high amount of bioflocs in the water may cause some physical damage to small-sized organisms. Recently, Schveitzer et al. (2013) observed a higher incidence of juvenile Litopenaeus vannamei with obstructed gills in tanks with total suspended solids between 800 and 1000 mg L−1, and shrimp mortality was also higher in these biofloc tanks. Many studies have assessed the use of BFT in intensive shrimp culture. Most studies, however, have been carried out in the nursery phase stocked with late post-larvae stages or in the grow-out rearing phase. Short- (15 days; Emerenciano et al., 2011) and long-term nursery trials (30 − 71 days; Correia et al., 2014; Mishra et al., 2008; Moss and Moss, 2004; Otoshi et al., 2001; Samocha et al., 2007; Suita et al., 2016; Wasielesky et al., 2013) stocked with young post-larvae (PL1 − PL12) are described in the literature. In general, results from these studies demonstrated the importance of bioflocs as a tool to prevent increase in ammonia and as a natural food source for post-larvae shrimp. Although these researches showed the viability of culturing PLs in the biofloc system, no study, to the best of our knowledge, has compared post-larvae performance between BFT and the microalgaebased system, a common practice associated with the nursery phase (Samocha, 2010; Samocha et al., 2002). Microalgae can have two functions in nursery operations: enhancing water quality by absorbing nitrogenous compounds and providing excellent supplemental nutrition (Juarez et al., 2010). These microorganisms have a high nutritional composition (Coutteau, 1996) and are known to be an essential food source during the early stages of shrimp growth (Juarez et al., 2010; Zmora et al., 2013). Therefore, culturing young post-larvae shrimp without the presence of microalgae rich in polyunsaturated fatty acids, as provided by microalgae-based systems, could compromise the animal’s performance. This study aimed to compare a microalgae-based system and the biofloc technology based on the performance of postlarvae L. vannamei reared under intensive nursery conditions. The effects of different concentrations of bioflocs on post-larvae performance were also assessed.

The experiment consisted of rearing post-larvae shrimp in three indoor nursery systems. One experimental group was reared in a conventional autotrophic system with daily water exchange and the addition of microalgae (herein called microalgae treatment). The other two experimental groups were reared using the biofloc system with dextrose (C6H12O6, Sigma–Aldrich®) addition and no water exchange. However, in the “Biofloc-500” treatment, the total suspended solids (TSS) were maintained at around 500 mg L−1, and in the “Biofloc-700” treatment, TSS were maintained at around 700 mg L−1. The experimental groups were randomly distributed in a unifactorial experimental design. Semi-cylindrical plastic tanks (92 cm × 68 cm × 25 cm) with a useful volume of 60 L constituted the experimental units. Three tanks were prepared for each experimental condition, resulting in nine experimental units. All tanks were equipped with linear aeration supplied by a perforated PVC pipe (90 cm long, 20 mm diameter with 36 holes of 1 mm) to maintain the solids in suspension and the oxygen concentration at appropriate levels for L. vannamei post-larvae rearing (> 5 mg L−1). Water temperature was kept constant, between 29 and 30 ∘C, using 100-W submersible heaters connected to a thermostat. At the beginning of the experiment, the microalgae treatment tanks were supplied with natural seawater (salinity of 35 g L−1) and the microalgae C. muelleri at a density of 10 × 104 cells mL−1. For biofloc treatments, the tanks were initially filled with natural seawater fertilized with a mixture of 35% protein shrimp feed and dextrose (15.3 g of feed + 23.7 g of dextrose). The water was prepared in a 390 L tank during the four consecutive days prior to the start of the experiment. TSS concentration on the last day of fertilization period was close to 100 mg L−1, and the estimated carbon:nitrogen (C:N) of the mixture of feed + dextrose was 20:1. C:N ratio was calculated according to Avnimelech (1999), considering 40% of carbon in the dextrose and 50% of carbon in the shrimp feed. For all treatments, the water was transferred to the experimental units on the first day of the experiment. Each experimental unit was stocked with 4000 post-larvae 6 (PL6) (length: 6.4 ± 0.3 mm; wet weight: 0.713 ± 0.002 mg; dry weight: 0.244 ± 0.020 mg), representing a stocking density of 67 PL L−1. The experiment was conducted until the post-larvae reached PL18 stage at 13 days after stocking. Water in the biofloc experimental units was not exchanged during the experimental period, but evaporated water was replaced with fresh water in order to maintain salinity. Furthermore, suspended solids were removed by filtering water through a 5-μm pore cartridge filter to maintain the required TSS levels for each biofloc treatment. The water of the microalgae treatment units was exchanged at rates of 100% per day. Subsequently, C. muelleri was counted in the water samples. To provide food for post-larvae and maintain water quality, microalgae were added as needed to maintain a concentration of 10 × 104 cells mL−1 (Juarez et al., 2010), The post-larvae shrimp were fed microencapsulated commercial diets (INVE™), and each tank received the same amount of feed. From PL6 up to PL18, Stresspak (40% crude protein) and Flake (48% crude protein) diets were fed twice and once a day, respectively. The PL Epac diet (45% crude protein) was fed six times a day from PL6 to PL10. Following this period and up to harvesting, post-larvae shrimp were fed the XL Epac diet six times a day (45% crude protein). Post-larvae were fed nine times a day (08:00, 10:00, 12:00, 14:00, 16:00, 18:00, 21:00, 23:00, and 03:00) and were provided feed quantities according to the manufacturer’s recommendations for each post-larval stage, as follows: PL6-8: 49 − 55 g/million PLs/feeding period; PL9-13: 65 − 73 g/million PLs/feeding period; PL14-18: 77 − 81 g/million PLs/feeding period.

2. Materials and methods 2.1. Biological material Nauplii of L. vannamei free of any pathogens that would require notification of the International Organization of Epizootics were acquired from Aquatec LTDA, Canguaratema, Rio Grande do Norte, Brazil. Nauplii were raised at a stocking density of 100 larvae L−1 in a 20 m3 semi-cylindrical hatchery tank in salinity of 35 g L−1 until reaching post-larvae (PL) stage 5 (PL5 = five-day-old). The microalgae Chaetoceros muelleri (5 × 104 cells mL−1) was added daily to the culture water. The larval and post-larval shrimp were fed nine times a day with microencapsulated commercial diets (INVE™). Artemia nauplii were also provided to the larvae at a rate of six nauplii for each mysis, or post-larvae, five times each day. Daily water exchange started at mysis stage (50% per day) and increased in the post-larvae stage (100% per day). When the larvae reached PL5, they were transferred to the experimental units.

2.3. Addition of carbohydrates Dextrose with 100% of carbohydrate was added daily (divided into four times per day) to the biofloc tanks to avoid accumulation of 141

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TSS and VSS were assessed using 0.6-μm fiberglass microfilters (GF6, Macherey-Nagel, Düren, Germany). TAN and nitrite analyses were carried out using a spectrophotometer and analyzed according to Strickland and Parsons (1972), following the guidelines contained in APHA (2005). Concentrations of chlorophyll a (Chl a) were used as a measure of phytoplankton biomass, and analyses followed EPA 445.0 methodology (Arar and Collins, 1997). Samples of known volume were filtered onto fiberglass microfilters (GF/F Whatman) until filter clogging. Chl a was evaluated after extraction of the pigment by submersion of filtered samples in 90% acetone solution for 24 h in the dark and cold (−15 ∘C). The pigment concentration was determined by a fluorometer (Turner Trilogy©, Sunnyvale, CA, USA), using a Chlorophyll NonAcidification kit (Turner 7200-046). The calibration of equipment was performed using a pure extract of Chl a, and for the extraction, the same solvent of the samples was used. 2.5. Post-larvae performance Performance parameters used to evaluate treatments included survival (%), post-larvae length (mm), and post-larvae dry weight (mg). Total length was measured from tip of the rostrum to the end of the telson (n = 15 for each tank). For analysis of dry weight, post-larvae were dried in an oven (45 °C) until constant weight (n = 150 each tank). At the end of the experiment, it was also examined survival (%) during a salinity stress test according to the methodology of FAO (2003). Salinity tests consisted of transferring 100 post-larvae abruptly from each replicate to cylinders containing 20 L of tap water for 30 min, then back to 35 g L−1 seawater for another 30 min. After that time, post-larvae survival was assessed by considering organisms that did not respond to mechanical stimulus as dead. In both salinities, the test water temperature was kept constant between 29 and 30 °C.

Fig. 1. Daily mean total (A) and un-ionized ammonia (B) in tanks of Litopenaeus vannamei post-larvae cultivated during 13 days (PL6–PL18) at a stocking density of 67 PLs L−1 in three nursery systems: conventional water-exchange system with daily addition of microalgae (Microalgae); biofloc system supplemented with dextrose and total suspended solids (TSS) at around 500 mg L−1 (Biofloc-500); and biofloc system supplemented with dextrose and TSS at around 700 mg L−1 (Biofloc-700). Values are means ± standard deviation.

2.6. Water consumption The final amount of water used by the experimental group was expressed in liters per thousand of post-larvae produced. This includes the initial water used to fill the experimental units and the water for daily water exchange in the microalgae group or fresh water used to replace evaporation losses in the biofloc groups.

nitrogenous wastes within the system. The daily input of carbohydrate required to neutralize ammonium excreted by shrimp was estimated by assuming that shrimp assimilate about 25% of the nitrogen added in the feed and that 75% of added nitrogen is transformed into ammonia dissolved in water (Avnimelech, 1999; Ebeling et al., 2006). From the 6th day, however, the estimated percentage of nitrogen assimilated by shrimp was reduced from 25% to 10% (90% of added nitrogen transformed into ammonia) as a result of accumulating ammonia in the water (Fig. 1A). For these calculations, the percentage of protein feed was considered to be the average of all types of feed used. The amount of dextrose added was calculated based on Avnimelech (1999) and Ebeling et al. (2006), assuming that 20 g of carbohydrate are needed to convert 1 g of total ammonia nitrogen (TAN) generated from feed into bacterial biomass. Even with a daily addition of dextrose, TAN increased beyond 1 mg L−1 in both biofloc treatments. This increase occurred four times during the experiment, and additional dextrose was added to the tanks to maintain TAN at 1 mg L−1 (carbohydrate:TAN ratio of 20:1).

2.7. Statistical analysis A one-way ANOVA, followed by the Student-Newman-Keuls (SNK) multiple-range test for mean separation (Zar, 2010) when necessary, was used for the comparison of treatments at the significance level of 0.05. Normality and homoscedasticity were assessed by the Shapiro–Wilk and Levene tests, respectively (Zar, 2010). Data expressed as a percentage underwent angular transformation before analysis. All statistical analyses were performed using the software package STATISTICA version 13.0 (Statsoft Inc., Tulsa, Oklahoma, USA). 3. Results Temperature, salinity, and nitrite were not significantly different among treatments (Table 1). Dissolved oxygen, pH, TAN, un-ionized ammonia (NH3eN) and chlorophyll a were significantly higher in microalgae treatment tanks, while alkalinity was higher in biofloc tanks (Table 1, Fig. 1). TSS, VSS and turbidity were significantly different among all treatments, with higher values occurring in the Biofloc-700 treatment (Table 1). No significant differences were observed in any post-larvae performance parameters, nor was salinity stress survival significantly different among treatments (Table 2). In contrast, water consumption during culture was significantly higher in microalgae treatment tanks (Table 2).

2.4. Water quality variables and chlorophyll a Dissolved oxygen and temperature (YSI 55, YSI Incorporated, Yellow Springs, OH, USA) were measured twice a day. Salinity (YSI 30, YSI Incorporated), pH (YSI 100, YSI Incorporated), TAN, and TSS (APHA, 2005 − 2540 D) were analyzed daily. Alkalinity (APHA, 2005 − 2320 B), nitrite and volatile suspended solids (VSS) (APHA, 2005 − 2540 E) were measured every 2 days, whereas turbidity (Turbidity meter 2171, ALFAKIT, Florianópolis, SC, Brazil) and chlorophyll a were analyzed every 3 days. 142

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performance in biofloc tanks was the same (P > 0.05) in tanks with mean TSS values of 500 or 700 mg L−1, indicating the tolerance of PLs to environments with large quantities of solids. Statistical differences among treatments were observed for some water quality variables, but the values remained within the appropriate range for larval culture of L. vannamei (Juarez et al., 2010). In microalgae treatment tanks, un-ionized ammonia (NH3eN) reached average values of 0.09 mg L−1 (Fig. 1B), which can be considered a safe level for rearing L. vannamei at PL1 (0.19 mg L−1; Cobo et al., 2014). As postlarvae survival was high in all treatments, it may be concluded that water quality did not interfere with post-larvae performance. Ammonia was controlled by different pathways in the experimental units. In microalgae treatment tanks, ammonia reduction was likely associated with its assimilation into microalgae biomass and daily water exchange. On the other hand, the concentration of chlorophyll a in biofloc tanks was close to zero, indicating a bacteria-dominated biofloc. In these tanks, the addition of dextrose stimulated the production of bacterial biomass from ammonia (Avnimelech, 1999), as represented by the increase in VSS (Schneider et al., 2006). In entirely heterotrophic systems, Ebeling et al. (2006) reported the absence of nitrite or nitrate production. In the present experiment, nitrite remained low during culture in biofloc tanks, suggesting that heterotrophic bacteria played a key role in the control of ammonia. In addition, alkalinity was not consumed, indicating that nitrification was not established during the course of the experiment. Since water was not exchanged in biofloc tanks, this system required only 12.9% of the water used by the microalgae treatment, thus conserving this resource. As expected, the mean values of TSS (∼ 700 mg L−1) and turbidity (∼ 60 NTU) were higher in Biofloc-700 tanks than in the other treatments. Considering the small size of post-larvae tested in this experiment, a higher amount of suspended solids in the water could be expected to cause some physical damage to organisms. For example, debris attached on appendices could affect the swimming or feeding activity of post-larvae, or even clog the gills. Regarding this latter point, Schveitzer et al. (2013) observed a higher incidence of juvenile L. vannamei with obstructed gills in biofloc tanks with TSS between 800 and 1000 mg L−1. Mortality was also higher in these tanks. In the present experiment, however, the post-larvae performance was similar in both Biofloc-500 and Biofloc-700 treatments, indicating that early post-larvae stages of L. vannamei can tolerate environments with large quantities of solids. TSS values tested in the present experiment are close to those suggested as adequate for L. vannamei juvenile culture in a biofloc system (Gaona et al., 2016; Schveitzer et al., 2013). Although not measured, it is reasonable to assume that post-larvae benefited from the natural food present in the culture tanks. Both microalgae and bioflocs are a source of natural food for cultured shrimp (Emerenciano et al., 2012; Juarez et al., 2010; Kent et al., 2011; Moss, 1994; Otoshi et al., 2011). Nevertheless, microalgae-based systems are more commonly used in the culture of larval and early post-larval stages of shrimp. This preference is justified by the high nutritional composition of microalgae (Coutteau, 1996). Diatoms, which were added daily to the microalgae treatment tanks, are readily digestible by shrimp (Jaime-Ceballos et al., 2006; Phillips, 1984). They have high protein quality and generally contain high levels of polyunsaturated fatty acids (PUFAs) (Brown et al., 1997; Phillips, 1984). Bioflocs also represent an important quality food source for shrimp (Avnimelech, 2012), but their composition and, hence, nutrient content may vary (see review in Martínez-Córdova et al., 2014). According to these authors, protein content of bioflocs may range from 14 to 50% (dry basis). Although it is reasonable to assume that bioflocs are a source of protein for shrimp, bacteria, which form the bioflocs, can be deficient in some important nutrients for shrimp (e.g., PUFAs) (Parkes and Taylor, 1983). In fact, the lipid content of bioflocs is generally low, ranging from 1.2 to 9.0%, but in most cases, it is closer to the lowest value (Martínez-Córdova et al., 2014). Therefore, considering nutritional differences between bioflocs and microalgae, a better post-larvae

Table 1 Water quality variables and chlorophyll a in tanks of Litopenaeus vannamei post-larvae cultivated during 13 days (PL6–PL18) at a stocking density of 67 PLs L−1 in three nursery systems: conventional water-exchange system with daily addition of microalgae (Microalgae); biofloc system supplemented with dextrose and total suspended solids (TSS) at around 500 mg L−1 (Biofloc-500); and biofloc system supplemented with dextrose and TSS at around 700 mg L−1 (Biofloc-700). Variables

Microalgae

Temperature (morning) (°C) 28.8 ± 0.3 Temperature (afternoon) (°C) 29.6 ± 0.7 Dissolved oxygen (morning) (mg L−1) 5.7 ± 0.1 a Dissolved oxygen (afternoon) (mg L−1) 5.8 ± 0.2 a Salinity (g L−1) 35.6 ± 0.0 pH 8.0 ± 0.0 a Alkalinity (mg CaCO3 L−1) 124.9 ± 5.8a Total ammonia nitrogen (mg TAN L−1) 1.00 ± 0.12 a NH3 − N (mg L−1) 0.06 ± 0.00 a Nitrite (mg NO3− − N L−1) 0.02 ± 0.00 Total suspended solids (mg L−1) 307.9 ± 5.8 a Volatile suspended solids (mg L−1) 76.5 ± 3.1 a Turbidity (NTU) 11.4 ± 1.4 a Chlorophyll a (μg L−1) 1.83 ± 0.08 a

Biofloc-500

Biofloc-700

28.5 ± 0.2

29.2 ± 0.6

30.3 ± 0.0

30.3 ± 0.5

5.4 ± 0.1

b

5.2 ± 0.2

b

5.2 ± 0.1

b

5.1 ± 0.1

b

35.7 ± 0.0 7.7 ± 0.0

35.9 ± 0.3

b

7.7 ± 0.0

141.6 ± 3.5b

b

134.7 ± 1.2b

0.52 ± 0.02

b

0.70 ± 0.04

b

0.02 ± 0.00

b

0.02 ± 0.00

b

0.01 ± 0.00

0.02 ± 0.01

536.5 ± 15.6 175.4 ± 8.8 45.1 ± 1.3

b

b

b

0.08 ± 0.03

681.0 ± 17.8

c

212.6 ± 17.1

c

59.5 ± 4.4 b

c

0.06 ± 0.05

b

Values are means ± standard deviation. Means with different letters in the same line indicate significant difference by one-way ANOVA followed by the SNK test (P < 0.05). Table 2 Performance parameters, salinity stress survival and water consumption in tanks of Litopenaeus vannamei post-larvae cultivated during 13 days (PL6–PL18) at a stocking density of 67 PLs L−1 in three nursery systems: conventional water-exchange system with daily addition of microalgae (Microalgae); biofloc system supplemented with dextrose and total suspended solids (TSS) at around 500 mg L−1 (Biofloc-500); and biofloc system supplemented with dextrose and TSS at around 700 mg L−1 (Biofloc-700)a. Parameter

Microalgae

Biofloc-500

Biofloc-700

94.4 ± 4.8

94.5 ± 9.1

95.6 ± 3.8

Survival (%) Final length (mm) 11.6. ± 0.2 11.5 ± 0.4 Final dry weight (mg) 1.351 ± 0.185 1.107 ± 0.095 Salinity stress survival (%) 95.2 ± 0.8 92.4 ± 3.4 Water consumption (L per thousand post-larvae) a 195.4 ± 9.8 26.1 ± 1.9 b

11.8 ± 0.4 1.277 ± 0.287 96.0 ± 3.0 24.2 ± 2.1

b

a Initial length: 6.4 ± 0.3 mm; Initial dry weight: 0.244 ± 0.020 mg. Values are means ± standard deviation. Means with different letters in the same line indicate significant difference by one-way ANOVA followed by the SNK test (P < 0.05).

4. Discussion Our study demonstrates that biofloc technology (BFT) can be just as effective as the microalgae-based system for the nursery of young L. vannamei post-larvae. This conclusion is based on the similarity of postlarvae performance parameters (P > 0.05) when animals were reared either in tanks inoculated with the diatom C. muelleri or in a bacteriadominated biofloc system. One important advantage of BFT over the microalgae-based system was lower water usage during culture by the absence of water renewal in biofloc tanks. In addition, post-larvae 143

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Litopenaeus vannamei (Boone) larvae. Aquac. Res. 45, 470–475. Correia, E.S., Wilkenfeld, J.S., Morris, T.C., Wei, L.W., Prangnell, D.I., Samocha, T.M., 2014. Intensive nursery production of the pacific white shrimp Litopenaeus vannamei using two commercial feeds with high and low protein content in a biofloc-dominated system. Aquacult. Eng. 59, 48–54. Coutteau, P., 1996. Micro-algae. In: Lavens, P., Sorgeloos, P. (Eds.), Manual on the Production and Use of Live Food for Aquaculture. Food and Agriculture Organization of the United Nations, Rome, pp. 7–48. De Schryver, P., Crab, R., Defoirdt, T., Boon, N., Verstraete, W., 2008. The basics of bioflocs technology: the added value for aquaculture. Aquaculture 277, 125–137. Ebeling, J.M., Timmons, M.B., Bisogni, J.J., 2006. Engineering analysis of the stoichiometry of photoautotrophic, autotrophic, and heterotrophic removal of ammonia-nitrogen in aquaculture systems. Aquaculture 257, 346–358. Emerenciano, M., Ballester, E.L.C., Cavalli, R.O., Wasielesky, W., 2011. Effect of biofloc technology (BFT) on the early postlarval stage of pink shrimp Farfantepenaeus paulensis: growth performance, floc composition and salinity stress tolerance. Aquacult. Int. 19, 891–901. Emerenciano, M., Ballester, E.L.C., Cavalli, R.O., Wasielesky, W., 2012. Biofloc technology application as a food source in a limited water exchange nursery system for pink shrimp Farfantepenaeus brasiliensis (Latreille, 1817). Aquac. Res. 43, 447–457. FAO, 2003. Health management and biosecurity maintenance in white shrimp (Penaeus vannamei) hatcheries in Latin America, FAO Fisheries Technical Paper 450. Food and Agriculture Organization of the United Nations, Rome. Gaona, C.A.P., Serra, F.P., Furtado, P.S., Poersch, L.H., Wasielesky, W., 2016. Biofloc management with different flow rates for solids removal in the Litopenaeus vannamei BFT culture system. Aquacult. Int. 24, 1263–1275. Godoy, L.C., Odebrecht, C., Ballester, E., Martins, T.G., Wasielesky, W., 2012. Effect of diatom supplementation during the nursery rearing of Litopenaeus vannamei (Boone, 1931) in a heterotrophic culture system. Aquacult. Int. 20, 559–569. Jaime-Ceballos, B.J., Hernandez-Llamas, A., Garcia-Galano, T., Villarreal, H., 2006. Substitution of Chaetoceros muelleri by Spirulina platensis meal in diets for Litopenaeus schmitii larvae. Aquaculture 260, 215–220. Jory, D., Cabrera, T., 2012. Marine shrimp. In: Lucas, J.L., Southgate, P.C. (Eds.), Aquaculture −Farming Aquatic Animals and Plants, second ed. Wiley-Blackwell, Chichester, pp. 476–513. Juarez, L.M., Moss, S.M., Figueras, E., 2010. Maturation and larval rearing of the pacific white shrimp, Penaeus vannamei. In: Alday-Sanz, V. (Ed.), The Shrimp Book. Nottingham University Press, Nottingham, pp. 305–352. Kent, M., Browdy, C.L., Leffler, J.W., 2011. Consumption and digestion of suspended microbes by juvenile Pacific white shrimp Litopenaeus vannamei. Aquaculture 319, 363–368. Martínez-Córdova, L.R., Emerenciano, M., Miranda-Baeza, A., Martínez-Porchas, M., 2014. Microbial-based systems for aquaculture of fish and shrimp: an updated review. Rev. Aquacult. 6, 1–18. Metcalf, Eddy Inc, 1991. Wastewater Engineering: Treatment, Disposal, Reuse, third ed. McGraw Hill, New York. Mishra, J.K., Samocha, T.M., Patnaik, S., Speed, M., Gandy, R.L., Ali, A.M., 2008. Performance of an intensive nursery system for the pacific white shrimp, Litopenaeus vannamei, under limited discharge condition. Aquacult. Eng. 38, 2–15. Moss, K.R.K., Moss, S.M., 2004. Effects of artificial substrate and stocking density on the nursery production of pacific white shrimp Litopenaeus vannamei. J. World Aquac. Soc. 35, 536–542. Moss, S.M., 1994. Growth rates, nucleic acid concentrations, and RNA/DNA ratios of juvenile white shrimp, Penaeus vannamei Boone, fed different algal diets. J. Exp. Mar. Bio. Ecol. 182, 193–204. Otoshi, C.A., Montgomery, A.D., Look, A.M., Moss, S.M., 2001. Effects of diet and water source on the nursery production of Pacific white shrimp Litopenaeus vannamei. J. World Aquac. Soc. 32, 243–249. Otoshi, C.A., Moss, D.R., Moss, S.M., 2011. Growth-enhancing effect of pond water on four size classes of pacific white shrimp, Litopenaeus vannamei. J. World Aquac. Soc. 42, 417–422. Parkes, R.J., Taylor, J., 1983. The relationship between fatty acids distributions and bacterial respiratory types in contemporary marine sediments. Estuar. Coast Shelf Sci. 16, 173–189. Phillips, N.W., 1984. Role of different microbes and substrates as potential suppliers of specific essential nutrients to marine detritivores. Bull. Mar. Sci. 35, 283–298. Racotta, I.S., Palacios, E., Ibarra, A.M., 2003. Shrimp larval quality in relation to broodstock condition. Aquaculture 227, 107–130. Racotta, I.S., Palacios, E., Hernandez-Herrera, R., Bonilla, A., Ramirez, J.L., 2004. Criteria for assessing larval and postlarval quality in white pacific shrimp (Litopenaeus vannamei, Boone, 1931). Aquaculture 233, 181–195. Rocha, I.P., Silva, L.S.R., Carvalho, R.A., 2003. Secondary Nurseries Support Changing Needs of Growing Shrimp. The Advocate Nov/Dec. pp. 75–76. Samocha, T.M., Guajardo, H., Lawrence, A.L., Castille, F.L., Speed, M., Mckee, D.A., Page, K.I., 1998. A simple stress test for Penaeus vannamei post-larvae. Aquaculture 165, 233–242. Samocha, T.M., Hamper, L., Emberson, C.R., Davis, A.D., McIntosh, D., Lawrence, A.D., Van Wyk, P.M., 2002. Review of some recent developments in sustainable shrimp farming practices in texas, arizona, and florida. J. Appl. Aquacult. 12, 1–42. Samocha, T.M., Gandy, R.L., McMahon, D.Z., Mogollón, M., Smiley, R.A., Blacher, T.S., Wind, A., Figueras, E., Velasco, M., 2003. The role of shrimp nursery systems to improve production efficiency of shrimp farms. In: Jory, D.E. (Ed.), Responsible Aquaculture for a Secure Future. The World Aquaculture Society, Baton Rouge, pp. 179–195. Samocha, T.M., Patnaik, S., Speed, M., Ali, A., Burger, J., Almeida, R., Ayub, Z., Harisanto, M., Horowitz, A., Brock, D.L., 2007. Use of molasses as carbon source in

growth in tanks with diatoms could be expected, but this was not observed in the present study. In contrast, Godoy et al. (2012) observed that L. vannamei juveniles cultured in diatom medium had better performance than shrimp cultured in biofloc medium, but the chlorophyll a concentrations (553.8 μg L−1) in diatom medium were much higher than those recorded in the present study (1.83 μg L−1). Herein it is reported that intensive nursery of young L. vannamei post-larvae (PL6–PL18) resulted in similar (P > 0.05) survival and growth when animals were reared either in bacteria-dominated biofloc tanks or in a microalgae-based system. In addition, survival in the salinity stress tests, which can be an indicator of post-larvae quality (FAO, 2003; Juarez et al., 2010; Racotta et al., 2004; Racotta et al., 2003; Samocha et al., 1998), was high and not significantly different among treatments (> 90.0%). The values were greater than 80.0%, which is characteristic of strong PLs (Juarez et al., 2010). These results indicate that the use of a bacteria-dominated biofloc system can produce young shrimp post-larvae with results comparable to those obtained with a microalgae-based system in nursery phase. Post-larvae performance was similar, whether in the biofloc tanks or the microalgae-based system, and a potential explanation for this outcome is suggested here. The high quality feed applied frequently in the tanks may have supplied the essential nutrients required to maintain good performance of post-larvae in all tanks, quite independent of the presence of natural food. This explanation is supported by recent findings of Suita et al. (2016), who demonstrated that as L. vannamei post-larvae grew from PL1 to PL30, the contribution of the inert feed was higher when compared to natural food present in bioflocs. The present results have practical implications for shrimp culture. Reduction in the amount of water required for the nursery phase of shrimp culture would reduce the costs associated with pumping, disinfection and heating of water, in addition to decreasing environmental impacts and improving biosecurity. Moreover, providing shrimp with microalgae by producing them in the laboratory requires adequate facilities and skilled labor, which, in turn, would increase production costs. On the other hand, growing microalgae through inorganic fertilization in advance of stocking can be a time-consuming process. Therefore, the application of in situ BFT by co-culture of post-larvae and heterotrophic bacterial biomass within the same solution can be advantageous since bacteria grow fast regardless of sunlight availability. To improve upon the results obtained here, future studies should evaluate higher post-larvae stocking densities in a biofloc system. Acknowledgements The authors would like to thank CNPq for the postdoctoral grant awarded to Rodrigo Schveitzer (Process 151032/2012-2) and research fellowships for Felipe Vieira and Walter Seiffert (process numbers PQ 309868/2014-9 and 302792/2012-0, respectively). We thank Efrayn Wilker Souza Candia, Douglas Valter Severino, and Adriano Machado da Silva for support in conducting the experiment. References APHA American Public Health Association, 2005. Standard Methods for the Examination of Water and Wastewater, first ed. Byrd Prepress, Washington. Arar, E.J., Collins, G.B., 1997. In Vitro Determination of Chlorophyll a and Pheophytin a in Marine and Freshwater Algae by Fluorescence (EPA Method 445.0). Environmental Protection Agency, Cincinnati. Avnimelech, Y., 1999. Carbon/nitrogen ratio as a control element in aquaculture systems. Aquaculture 176, 227–235. Avnimelech, Y., 2012. Biofloc Technology: A Practical Guide Book, second ed. The World Aquaculture Society, Baton Rouge. Browdy, C.L., Bratvold, D., Stokes, A.D., McIntosh, R.P., 2001. Perspectives on the application of closed shrimp culture systems. In: Browdy, C.L., Jory, D.E. (Eds.), The New Wave, Proceedings of the Special Session on Sustainable Shrimp Culture. The World Aquaculture Society, Baton Rouge, pp. 20–34. Brown, M.R., Jeffrey, S.W., Volkman, J.K., Dunstan, G.A., 1997. Nutritional properties of microalgae for mariculture. Aquaculture 151, 315–331. Cobo, M.L., Sonnenholzner, S., Wille, M., Sorgeloos, P., 2014. Ammonia tolerance of

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R. Schveitzer et al.

Strickland, J.D.H., Parsons, T.R., 1972. A Practical Handbook of Seawater Analysis (bulletin 167), second ed. Fisheries Research Board of Canada, Ottawa. Suita, S.M., Braga, A., Ballester, E., Cardozo, A.P., Abreu, P.C., Wasielesky, W., 2016. Contribution of bioflocs to the culture of Litopenaeus vannamei post-larvae determined using stable isotopes. Aquacult Int 24, 1473–1487. Wasielesky, W., Froes, C., Foes, G., Krummenauer, D., Lara, G., Poersch, L., 2013. Nursery of Litopenaeus vannamei reared in a biofloc system: the effect of stocking densities and compensatory growth. J. Shellfish Res. 32, 799–806. Zar, J.H., 2010. Biostatistical Analysis, fifth ed. Prentice Hall, New Jersey. Zmora, O., Grosse, D.J., Zou, N., Samocha, T.M., 2013. Microalgae for aquaculture. In: Richmond, A., Hu, Q. (Eds.), Handbook of Microalgal Culture. Willey-Blackwell, Oxford, pp. 628–652.

limited discharge nursery and grow-out systems for Litopenaeus vannamei. Aquacult. Eng. 36, 184–191. Samocha, T.M., 2010. Use of intensive and super-intensive nursery systems. In: AldaySanz, V. (Ed.), The Shrimp Book. Nottingham University Press, Nottingham, pp. 247–280. Schneider, O., Sereti, V., Machiels, M.A.M., Eding, E.H., Verreth, J.A.J., 2006. The potential of producing heterotrophic bacteria biomass on aquaculture waste. Water Res. 40, 2684–2694. Schveitzer, R., Arantes, R., Costódio, P.F., do Espírito Santo, C.M., Arana, L.V., Seiffert, W.Q., Andreatta, E.R., 2013. Effect of different biofloc levels on microbial activity, water quality and performance of Litopenaeus vannamei in a tank system operated with no water exchange. Aquacult. Eng. 56, 59–70.

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