Bull Environ Contam Toxicol DOI 10.1007/s00128-014-1227-4

Nutrient Budgets and Effluent Characteristics in Giant Freshwater Prawn (Macrobrachium rosenbergii) Culture Ponds Subhendu Adhikari • Bharat Chandra Sahu Abhijit S. Mahapatra • Lambodar Dey



Received: 24 September 2013 / Accepted: 4 February 2014 Ó Springer Science+Business Media New York 2014

Abstract It is important to understand nutrient budgets of aquaculture practices for efficiency of input resources and to utilize all output nutrient sources. The aim of the present study was to develop a nutrient budget for giant freshwater prawn (Macrobrachium rosenbergii) culture ponds. The study was conducted in farmer’s ponds (0.25–0.5 ha) of Odisha, India, and the results showed that feed accounted 97 % total nitrogen (N), 98.7 % total phosphorus (P) and 90 % total organic carbon (OC), respectively. The harvested prawn accounted for recovery of 37 % N, 10 % P and 15 % OC, respectively. The N, P and OC accumulated in sediment were 52 %, 76 %, and 65 %, respectively. Nutrient loads in the effluents were 2.22 ± 0.66 kg inorganic N, 0.40 ± 0.15 kg P, and 21.01 ± 6.4 kg OC per ton of prawn production. The present study implicated that high nutrient values observed in both water and sediment provide important opportunities for nutrient reuse through pond sediment applications to croplands as an organic S. Adhikari (&) Soil and Water Chemistry Section, Division of Aquaculture Production and Environment, Central Institute of Freshwater Aquaculture, P.O. Kausalyaganga, Bhubaneswar 751002, Odisha, India e-mail: [email protected] B. C. Sahu Aquaculture Division, Balasore 756003, Odisha, India e-mail: [email protected] A. S. Mahapatra Computer Centre, Central Institute of Freshwater Aquaculture, P.O. Kausalyaganga, Bhubaneswar 751002, Odisha, India e-mail: [email protected] L. Dey K.K.S. Women’s College, Balasore, Odisha, India e-mail: [email protected]om

manure, as well as pond water irrigation to crops as a ‘‘liquid fertilizer’’. Keywords Prawn (Macrobrachium rosenbergii)  Nutrient budget  Carbon  Nitrogen  Phosphorus Aquaculture activities involve a variety of inputs for giant freshwater prawn (Macrobrachium rosenbergii) production including manures, fertilizers, feed and a combination of all these things. A good amount of nutrients are lost in the system during the culture period. Most of those lost nutrients are distributed in water, prawn biomass and sediments of the pond systems. It is generally believed that a large proportion of nutrients received in ponds end up in pond sediment and discharged effluents (Lin et al. 1997). To reduce the nutrient losses in discharged water, it is essential to estimate the nutrient budgets to assess the fate of nutrients added to the pond culture systems. Nutrient budgets could permit quantification of potential pollution impact of a specific pond management strategy. Chemical budgets have been formulated for experimental ponds containing channel catfish (Boyd 1985), striped bass (Daniels and Boyd 1989), tilapia (Green and Boyd 1995) and high densities of shrimp (Hopkins et al. 1993; Martin et al. 1998). Nitrogen (N) and Phosphorus (P) budgets were formulated for commercial shrimp ponds in Thailand (Briggs and Funge-Smith 1994; Thakur and Lin 2003), extensive shrimp ponds in Bangladesh (Wahab et al. 2003), semi-intensive shrimp farms in Mexico (Paez-Osuna et al. 1997), and intensive shrimp farms in Australia (Jackson et al. 2003). Nutrient budgets of freshwater prawn (Macrobrachium rosenbergii) culture are not well documented particularly in India. The present study reports nutrient budgets for organic carbon (OC), nitrogen (N) and phosphorus (P) in prawn culture and nutrient loads in the effluents in eastern India.

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Materials and Methods Field studies were conducted in five ponds of prawn culture having 0.25–0.5 ha area in two different districts of Balasore and Bhadrak of Odisha, India. The average depths of these ponds varied between 1.0 and 1.5 m with an average depth of 1.2 m. The prawn culture was done using organic fertilizer. All ponds were limed with 200 kg/ha of limestone at the time of pond preparation. The organic fertilizer, fermented rice straw (Oryza sativa) at 250 kg/ha was used to fertilize the ponds. The fermented straw was prepared by mixing 100 kg of rice straw, 5 kg Ca(OH)2 and 1 kg yeast with 200 L of pond water, and fermented for 24 h. This mixture was then applied in the early morning at about 0700 to 0800 hours to these ponds in equal amounts at weekly intervals. During the fertilizer application, aerators were always operated. The fertilization in the pond helped to develop plankton. After sufficient plankton development, the larvae of prawn were stocked in these ponds at stocking density of 3.9 ± 0.5/m2. The average size of prawn was 16–17 mm post larvae (PL). The pelleted feed containing 24–32 % protein was used to feed the prawn. The duration of culture was 200 days. No water exchange was performed during the culture period. At the end of culture period, the mean of fresh body weight (MWT), feed conversion ratio (FCR), survival rate and total biomass of prawn were determined. The MWT was calculated from total weight of ten randomly selected fresh prawns at harvest divided by ten. The FCR was calculated as total weight of dry feed given divided by the total weight gain. Survival rate was determined as 100 (final total prawn number divided by the initial total prawn number) and total biomass as final total prawn weight per crop. The survival rate of the prawn was 72 ± 10 %. At harvest time, the average weight of prawn was 69 ± 8 g, respectively. The production was 1,972 ± 481 kg/ha. The FCR was 1.76 ± 0.03. Total N, P, and OC input, output, uptake and accumulation in the culture system during the culture period were measured. Nutrient budgets were calculated based on inputs from water, fertilizer and feed; and outputs were calculated based on harvested prawn, drained water and sediment. Nutrient input and output in the form of water was calculated by multiplying the nutrient concentration with total water volume. Nutrient input in the form of water represents nutrient contained in water on the day of prawn stocking, as water sample was collected on the same day prior to prawn stocking. Nutrients output in the form of water represents nutrient contained in water on the harvest day; column water sample was taken to measure final nutrients concentration in water prior to pond draining. Soil samples were collected by taking six cores (up to 15 cm depth) from each pond, and mixed in a composite sample

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for analysis; final sample was taken on the harvest day prior to pond draining. These samples were air dried, pulverized to pass a 0.25-mm screen and analyzed for OC, N and P. Nutrient concentration in the initial and final soil sample was measured to calculate nutrient surplus in the soil over the study period; the calculation was as follows: total nutrient content in sediment = nutrient concentration in the sediment 9 total mass, total mass was calculated from mean bulk density. The collected soil samples before prawn stocking and at harvesting were analyzed for total N content (Raive and Avnimelech 1979). The total P of the soil was analyzed by persulphate digestion followed by ascorbic acid method (APHA 1989). Total OC of the soil was determined using Walkley and Black (1934) rapid titration method. Total N, P and OC concentration was also analyzed for prawn feed, organic fertilizer (rice straw) and carcasses of harvested prawn following the methods used for the sediment. For this, these were freeze-dried and pulverized to pass a 0.85-mm screen. Nutrient input in the form of feed was calculated as follows: nutrient (N/P/C) in feed = nutrient concentration in feed 9 total amount of feed supplied. Nutrient output in the form of prawn was calculated as follows: nutrient (N/P/C) in prawn = nutrient concentration in prawn carcasses 9 total prawn biomass. Mean prawn weight was determined as the difference of weight at initial and final harvest. Water quality of prawn culture ponds measured biweekly at 10.00 hours. Total ammonia nitrogen (NH4-N) in water was measured by phenate method (APHA 1989), nitrite nitrogen (NO2-N) was analyzed by colorimetric method using the Griess reaction (APHA 1989), nitrate nitrogen (NO3-N) was measured using brucine sulphate method (APHA 1989), soluble reactive phosphate (SRP) was determined by ascorbic acid method (APHA 1989), and total phosphorus was estimated by acid digestion (APHA 1989). Total alkalinity and Chlorophyll-a concentration were determined by APHA (1989).Total dissolved organic carbon (DOC) was determined by APHA (1989). Temperature, dissolved oxygen (DO), and pH (at 20 cm below the water surface) were measured weekly in situ. The water quality of these prawn culture ponds were as follows: Water pH ranged from 7.1 to 8.0 throughout the experimental period. Overall DO concentration varied from 4.5 to 5.2 mg/L. The NH4-N, NO2-N and NO3-N ranged from 0.015 to 0.14, 0.005 to 0.09 and 0.040 to 0.26 mg/L, respectively. The SRP ranged from 0.003 to 0.03 mg/L while total phosphate ranged from 0.007 to 0.05 mg/L. Total DOC ranged from 1.5 to 3.8 mg/L in the water. The total alkalinity concentrations varied from 80 to 130 mg/L as CaCO3. Overall mean of Secchi disk depths ranged from 13 to 28 cm. Chlorophyll-a concentration increased with the progress of culture, and at the end of the culture period, chlorophyll-a reached as high as from 0.20 to 0.45 mg/l.

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Nutrient loads in the effluent were calculated as follows: nutrient concentration in discharge water 9 volume of effluent. Total volume of effluent was considered as the 90 % of total water volume in the pond as some water will be always remain in the pond bottom during the harvesting of prawn. Quality control (QA/QC) was done for all the samples. A reagent blank was analyzed with every set of samples that are extracted or digested. This reagent blank includes any and all reagents that were used in the analytical process and was carried through the entire process, including extraction and filtering or digestion. At least ten percent of samples were analyzed in duplicate. The first, last and every tenth sample were run in duplicate. Duplicate values typically were within 8 % of each other for all samples. At least one standard reference material was analyzed with each set of samples. Samples run with a standard reference material that falls outside the acceptable range were reanalyzed, including digestion or extraction if necessary. One way ANOVA was done along with post hoc analysis for the variance among the nutrients retention and recovery, if any using the statistical software SPSS (14.0).

Results and Discussion The results of N, P and OC budgets (i.e., input and output) are presented in Table 1. Nutrient budgets revealed that feed was the major input of N, P and OC. The N, P and OC inputs in the form of feed were 97 %, 98.7 % and 90 %, respectively. The N, P and OC in the form of water were 0.5 %, 0.3 % and 1.2 %, respectively. The N, P and OC inputs in the form of organic fertilizer were 2.5 %, 1.0 % and 8.8 % of the total inputs, respectively. Nutrients retained by the prawn flesh could be considered as the nutrient gain in the culture system while nutrients retained by the water, sediment and others (unaccounted) could be considered as nutrient loss in the system. Nutrient budgets revealed that the major portion of the nutrient inputs was deposited in the sediment. N, P and OC accumulated in sediment were 52 %, 76 % and 65 %, respectively of total nutrient retention in the culture system. In addition, nutrient budgets also showed that during the culture period some of the N, P and OC went unaccounted. Unaccounted N was 8 % of the total nutrient retention, while unaccounted P was 12 % of the total nutrient retention in the system. Unaccounted OC was 17 % of the total nutrient retention of the system. The N, P and OC output in the discharged water during harvest were 3 %, 2 %, and 3 %, respectively. The N, P and OC retained (recovered) in the prawn flesh were 37 %, 10 %, and 15 %, respectively of the total inputs.

Table 1 Input, output and budgets of nitrogen, phosphorus and organic carbon (kg/ha) in the Macrobrachium rosenbergii culture ponds using organic inputs (n = 15) Parameters

Nitrogen (N)

Phosphorus (P)

Organic Carbon(OC)

Input Water

0.26 ± 0.06

0.04 ± 0.01

6.17 ± 1.39

Organic fertilizers

1.44 ± 0.39

0.17 ± 0.04

45.67 ± 13.06

54 ± 9

16 ± 3

466 ± 76

Water

1.51 ± 0.23

0.27 ± 0.07

14.42 ± 3.65

By harvest of prawn

20.5 ± 3.4

1.6 ± 0.3

79.3 ± 13.2

Feed Output

Sediment

28.9 ± 5.9

12.3 ± 2.4

337 ± 61

Unaccounted

4.79 ± 1.36

2.04 ± 0.12

87.12 ± 13.8

There was homogeneity of variance among the group of the retention of N, P and OC in five ponds as per Levene’s homogeneity of variance test. The significant value was calculated as 0.844 (p = 0.844 [ 0.05). The one way ANOVA showed the significance value of 0.998 which was greater than 0.05 and hence there was no significant difference between group means. In case of recoveries of N, P and OC in these ponds, it has been observed that there was homogeneity of variance as revealed by Levene’s test of homogeneity of variance with significance value calculated to be 0.879 (p = 0.879) which was greater than 0.05. The one way ANOVA showed the significance value of 0.993 which was greater than 0.05 and hence there was no significant difference between group means. Nutrient loads in the effluents of organically based prawn culture ponds are presented in Table 2. The volume of effluents from all the grow out ponds was 3,880 ± 945 m3 with total inorganic N of 1.51 ± 0.32 kg, total P of 0.27 ± 0.06 kg, and total OC of 14.42 ± 4.41 kg, respectively. These nutrients load were equivalent to 2.22 ± 0.66 kg of inorganic N, 0.40 ± 0.15 kg of P, and 21.01 ± 6.4 kg of total OC per ton of prawn. Total load of nutrients in the effluents increased from first month till harvesting period. The N, P and OC retained (recovered) in the prawn flesh in the present study were 37 %, 10 %, and 15 %, respectively of the total inputs. The utilization of N was reported to be 20 % to 32 % in intensive quasi-closed water ponds for tilapia. The utilization of P in tilapia culture systems ranged from 10 %–20 % (Green and Boyd 1995). Siddiqui and Al-Harbi (1999) reported 21.4 % N and 18.8 % P were converted into the flesh of hybrid tilapia harvested from the tanks. The red tilapia could capture 32.53 % N and 15.98 % P from the input feed in a recirculatory aquaculture system. Mean conversion of feed N and P to shrimp flesh averaged 74 % and 40 %, respectively in a semi-intensive coastal

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Bull Environ Contam Toxicol Table 2 Nutrient loads in the effluents of Macrobrachium rosenbergii culture ponds (n = 15) Parameters

Average load in the effluents per pond

Total load per ton of prawn

Volume of effluents (m3)

3,880 ± 945



Total inorganic nitrogen (kg)

1.51 ± 0.32

2.22 ± 0.66

Total phosphorus (kg)

0.27 ± 0.06

0.40 ± 0.15

14.42 ± 4.41

21.01 ± 6.4

Total organic carbon (kg)

brackish water culture in Bangladesh (Islam et al. 2004). Higano and Pichitkul (2000) reported that 16 %–19 % of the C composition of feed was converted into prawn (Penaeus monodon) while 25 %–30 % of the N composition of feed was converted into prawn in intensive culture of prawn in freshwater areas of Thailand. The amount of nutrients converted into the prawn flesh is almost comparable with these reports. The results of conversion of nutrients into different species varies mainly because of different stocking densities, different culture systems like close culture systems, water exchange culture systems, only feed based culture, feed-fertilizer-manure based culture systems, aquaculture integrated with mangrove, rice etc. Sediment plays an important role in the balance of an aquaculture system; it can act as a buffer in water nutrient concentration (Chien and Lai 1988). The large amount of unaccounted for N could be due to losses through denitrification process in the sediment. Diab and Shilo (1986) reported that when ponds were refilled, anaerobic conditions developed beneath the soil surface, and NO3-N was converted to N gas by denitrification. Sedimentation is generally considered a main mechanism for P loss in ponds because sediments are known to have a strong affinity for P (Shrestha and Lin 1996). Though the sediment contains sufficient nutrients and feeding the prawn also adds nutrients to the ponds, these nutrients are trapped into different forms (water soluble, exchangeable, Fe–Mn oxides, organic matter association, silicate, clay minerals etc.) in the sediments. The release of nutrients from the sediment to the overlying water for plankton production depends on the type of sediment, pH, redox potential etc. Thus, the nutrient rich sediment would not create any problem to the prawn. In addition, up to 2.5 cm of bottom sediments are removed from the ponds every year. Denitrification and ammonia volatilization are two potential losses of N that are not often measured directly in the culture systems. Therefore, in most studies, including the present study, these factors are estimated indirectly as the difference between the N inputs and outputs. In the

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present study, an average of 8 % N was estimated as lost via these processes. However, widely varying results have been reported in different studies. Most of the studies estimated less than 15 % of N as unaccounted (Martin et al. 1998; Briggs and Funge-Smith 1994). However, much higher losses from 27.4 % to 66 % have also been reported (Boyd 1985; Paez-Osuna et al. 1997). Green and Boyd (1995) reported that nutrient losses in pond at draining were 7 %–9 % of total N, 29 %–37 % of total P and 2 %–3 % of COD. Holby and Hall (1991) reported that the environmental loss of P for each ton of fish produced was 19.6–22.4 kg, and of the loss to the environment, 34 %–41 % was in dissolved form and 59 %–66 % was accumulated in the sediment. During the emptying operation, 630 and 2,830 kg/ha of suspended matter, 10.8 and 36.5 kg/ha of total N and 1.2 and 5.1 kg/ ha of total P were discharged from the pond during drought and heavy rainfall (50.5 mm in 166 h), respectively (Banas et al. 2002). Net N discharged from semi-intensive shrimp farms were reported to be 9.7 kg (Phillips 1994) per ton of shrimp production. The P loads of trout farms using Karasu stream, Turkey ranged from 6.25 to 14.50 kg per ton of rainbow trout fish produced (Pulatsu et al. 2004). The P loads of Nordic trout farms per ton of fish produced were reported to be 4.8 to 6.0 kg (Bergheim and Cripps 1998; Enell 1995). It is evident from the present study that the nutrient discharges from the prawn ponds were much lower than that from the shrimp and trout farms. All aquaculture pond effluents containing N, P and OC are typically discharged into adjacent water bodies, regardless of their type and what ecological value they may hold. Some farms directly discharge into rice fields or gardens for vegetables cultivation (Phan et al. 2009), and some nutrients will be retained in the pond sediment or taken up by other biota in the environment. The development of Best Management Practices (BMPs) will lead to further improvement in fertilizers and feed efficacies and water management regimes, which ultimately lead to significant reductions in N, P and OC discharge levels and thereby contribute to the sustainability of the prawn culture system and to improved environmental integrity (De Silva et al. 2010). From the present investigation it is evident that 37 % N, 10 % P and 15 % C of the total inputs were converted into prawn flesh. Total accumulations of N, P and OC in pond’s sediment were 52 %, 76 %, and 65 %, respectively. High nutrient content of the pond bottom sediment makes it suitable to be used as fertilizer but this should be done judiciously so that the crop soils should not be polluted. The effluents from all grow out ponds contained appreciable amount of N, P and C. This nutrient enriched pond water could be used as liquid fertilizer for horticultural crops. In this regard, further research is to be conducted for

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the utilization of pond sediment as fertilizer and pond water as irrigation water as well as liquid fertilizer. In addition, the appropriate rationing and use of high quality feeds to maximize growth while minimizing waste losses will help to lessen the potential environmental impacts of prawn culture pond operations. Lastly, the use of pond sediments and water in fertilizer applications should only be completed following their nutrient content analyses in order to appropriately estimate application rates of these materials under nutrient remediation practices. Acknowledgements The authors are grateful to the Director of Central Institute of Freshwater Aquaculture for providing necessary facilities to carry out the present work. The authors are also grateful to the farmers for their generous help for carrying out the present study in their ponds.

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Nutrient budgets and effluent characteristics in giant freshwater prawn (Macrobrachium rosenbergii) culture ponds.

It is important to understand nutrient budgets of aquaculture practices for efficiency of input resources and to utilize all output nutrient sources. ...
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