Comparison of water quality and production performance of barramundi (lates calcarifer) fingerlings in two systems

MINISTRY OF EDUCATION AND TRAINING NHA TRANG UNIVERSITY VO THI LUU COMPARISON OF WATER QUALITY AND PRODUCTION PERFORMANCE OF BARRAMUNDI Lates calcarifer FINGERLINGS IN TWO SYSTEMS: A

MINISTRY OF EDUCATION AND TRAINING

NHA TRANG UNIVERSITY

VO THI LUU

COMPARISON OF WATER QUALITY AND PRODUCTION

PERFORMANCE OF BARRAMUNDI (Lates calcarifer)

FINGERLINGS IN TWO SYSTEMS: A RECIRCULATION

SYSTEM AND A FLOW-THROUGH SYSTEM

MASTER THESIS

KHANH HOA - 2018

MINISTRY OF EDUCATION AND TRAINING

NHA TRANG UNIVERSITY

VO THI LUU

COMPARISON OF WATER QUALITY AND PRODUCTION

PERFORMANCE OF BARRAMUNDI (Lates calcarifer)

FINGERLINGS IN TWO SYSTEMS: A RECIRCULATION

SYSTEM AND A FLOW-THROUGH SYSTEM

MASTER THESIS

and Climate Change

Topic allocation Decision 1011/QD-DHNT dated

UNDERTAKING

I undertake that the thesis entitled: “Comparison of water quality and performance of Barramundi (Lates calcarifer) fingerlings in two systems: a recirculation systems and a flow-through system” is my own work The work has not

been presented elsewhere for assessment until the time this thesis is submitted

NhaTrang, 02nd May 2018

ACKNOWLEDGMENT

I would like to express the deepest appreciation to the Faculty of Graduate Studies, Nha Trang University (NTU) for the helping and giving best conditions me finish my thesis

My special thanks go to Dr Le Anh Tuan for the continuous support of my study, for his patience, motivation, enthusiasm, and immense knowledge My gratitude

is always there with all the Lecturers and the coordinators of the Norhed Master’s Programme

I sincerely would like to thank the collaboration of the Australis Aquaculture Vietnam Ltd Company (Ninh Hoa, Khanh Hoa, Vietnam) where the recirculating system was constructed and all the data collections were carried out I am grateful with

Mr Daniel Fisk, the Managing Director of AAV and all of the colleagues from nursery farm, RAS team and laboratory for their supports

Last but not the least, to thank my family and my friends for always concern and encourage me during the past time

Thank you!

NhaTrang, 02nd May 2018

TABLE OF CONTENTS

UNDERTAKING i

ACKNOWLEDGMENT ii

TABLE OF CONTENTS iii

LIST OF SYMBOLS v

LIST OF ABBREVIATIONS vi

LIST OF TABLES vii

LIST OF FIGURES viii

ABSTRACT 1

Chapter 1: INTRODUCTION 2

Chapter 2: LITERATURE REVIEW 5

2.1 Recirculation aquaculture system 5

2.2 Barramundi, distribution and production 8

2.3 Nursery phase 11

Chapter 3: MATERIALS AND METHOD 12

3.1 Study site 12

3.2 Production setup 14

3.3 Water quality 14

3.4 Barramundi production parameters 17

3.5 Statistical analysis 19

Chapter 4: RESULTS AND DISCUSSION 20

4.1 Water quality 20

4.1.1 Water quality in the RAS 20

4.1.2 Comparison of water quality between the RAS and the FTS 21

4.1.3 Discussion 22

4.2 Barramundi production performance 25

4.2.1 Comparison of barramundi production parameters between the FTS and the RAS 25

4.2.2 Discussion 29

4.3 Preliminary assessment of comparative economics 30

4.3.1 Comparison of economic parameters between the RAS and the FTS 30

4.3.2 Discussion 32

Chapter 5: CONCLUSION AND RECOMMENDATION 34

5.1 Conclusion 34

5.2 Recommendation 34

REFERENCES 35 APPENDICES

LIST OF SYMBOLS

B : Biomass

Bf : The final biomass

Bi : The initial biomass

F : Feed consumption

m1 : The pre weight

m2 :The post weight

P : Population

Pf: :The final population

Pi : The stocking population

t : Time

W : Weight of fish

Wf : The final weight

Wi : The initial weight

LIST OF ABBREVIATIONS

AAV : Australis Aquaculture Vietnam AGR : Absolute growth rate

CO2 : Carbon dioxide DFI : Daily feed intake

DO : Dissolved oxygen FAO : Food and Agriculture Organization FCR : Feed conversion ratio

FRP : Fiberglass reinforced plastic FTS : Flow-through system

NH3 : ammonia

NH4 : ammonium

NO2 : nitrite

NO3 : nitrate RAS : Recirculation aquaculture system

SR : Survival rate SGR : Specific growth rate TSS : Total suspended solids

UV : Ultraviolet

LIST OF TABLES

Table 3.1: Environmental parameters 15 Table 4.1: Mean values for environmental parameters in RAS (mg.L-) (N = 12) 20 Table 4.2: Compare mean values of environmental parameters between the RAS and

the FTS (NS, no significant difference; *, significant difference, P < 0.05) 22

Table 4.3: The stocking data of barramundi fingerlings in the FTS and in the RAS 25 Table 4.4: The mean values for barramundi production performance in the FTS and in

the RAS 27 Table 4.5: Summary of all parameters monitored from October 2014 to September

2015 with FTS and from October 2015 to September 2016 with RAS at the AAV facility 31

LIST OF FIGURES

Figure 2.1: Schematic diagram of a basic RAS 5

Figure 2.2: A RAS compared with a traditional FTS 6

Figure 2.3: Distribution map for Lates calcarifer 8

Figure 2.4: Main producer countries of Lates calcarifer 9

Figure 2.5: Global aquaculture production for Lates calcarifer 10

Figure 3.1: Small tanks in AAV nursery 12

Figure 3.2: A schematic design of the basic components of AAV nursery 13

Figure 3.3: Oxygen meters in AAV nursery 16

Figure 4.1: The mean values for pH, DO (mg.L-) and CO2 (mg.L-) in the RAS 21

Figure 4.2: Population and fish weight of nursery period in the FTS and in the RAS 26

Figure 4.3: Survival rate in the FTS and in the RAS during nursery phase 27

Figure 4.4: Feeding rate and growth rate in the FTS and in the RAS of nursery period 28

Figure 4.5: Feed conversion ratio in the FTS and in the RAS of nursery phase 29

Comparison of water quality and production performance of Barramundi

(Lates calcarifer) fingerlings in two systems: a recirculation system and a

flow-through system

ABSTRACT

The comparison of water quality and barramundi (Lates calcarifer) production

performance were conducted using the recirculation system and the flow-through system of Australis Aquaculture Vietnam (AAV) as an adaption option in the context

of climate change The goals were; (1) to evaluate and compare the important environmental parameters of the RAS versus the FTS for the commercial nursery farm, (2) to compare the survival, feeding rate, growth rate and FCR of barramundi production between RAS and FTS in the nursery phase, (3) preliminary assessment of economic budget between two systems All information in this study and production scale were based on the technology design and production parameters existing at the AAV facility

pH and dissolved oxygen concentrations were lower in the RAS (7.2 ± 0.13, 5.8

± 0.41) compared to in the FTS (8.2 ± 0.13, 6.3 ± 0.58) The mean values of nitrite and nitrate were higher in the RAS (1.3 ± 0.36 mg.L-, 49.6 ± 8.68 mg.L-) compared to in the FTS (0.4 ± 0.16 mg.L-, 25 ± 7.92 mg.L-), but the ranges of these levels in both systems were safe for aquaculture production Water temperature and ammonia concentrations were not significantly different between the RAS and the FTS In contrast to the high density of Vibrio bacteria (160 ± 72 CFU.mL-) and total bacteria (432 ± 283 CFU.mL-

) in water input of the FTS, no pathologies were detected in RAS water

Performance of barramundi fingerling production included survival rate, feeding rate, growth rate and FCR respectively were higher in the RAS (93.8%, 4.1%, 6.49% and 1.04) compared to in the FTS (79%, 3.5%, 5.84% and 0.99) Combined with the requirements of environmental parameters, the results confirmed that the RAS can produce more fish with high survival and less water consumption

Chapter 1: INTRODUCTION

Aquaculture production is playing an important role in food demand for human life Fish is also an important source of animal protein, providing livelihood opportunities and food security for millions of people Aquaculture accounts for 50 percent of the world’s food fish and can potentially be increased to 62 percent of fish for human consumption by 2030 (FAO, 2014) As the demand for aquaculture products increases, producers must expand current fish farms based on existing land and water resources by adopting new technology to enable higher rearing densities (Clark, 2003)

Flow-through systems (FTS) can be used in intensive farming if there is an abundant and easy to harness supply of clean water (Bijo, 2007) In a traditional flow-through system, water simply passes through tank culture of fish only once before it is discharged back to environment The flowing water transports oxygen to the fish and removes wastes out of the system (Bijo, 2007) However, this requires a large volume

of water resources and both water quantity necessary for fish production and amount

of pollutants out environment are very high Thus, the FTS do not satisfy requirements

of future trends in the environmental protection and especially water resources

preservation (Lang et al., 2012)

Recirculation aquaculture system (RAS) is one of the new methods used to increase aquaculture production after more than 30 years of research and development

(Timmon et al., 2007) In fish farms, a RAS includes the fish tanks, an adapted water

treatment system and pumps to maintain water flow The water treatment system is the center of the RAS that makes the system distinct from traditional FTS (Lekang, Odd-Ivar, 2013) With RAS, the outlet water from the fish tanks goes through the water treatment system, which includes physical, chemical and biological process to filter, clean and improve water quality before turning back through fish culture tanks, thus the amount of added new water can be reduced

In the context of climate change, worldwide aquaculture production is threatened to the sustainability (De Silva & Soto, 2009) The negative effects of

energy have directly impact on the productivity and profitability levels of this sector (Oguntuga, Adesina & Akinwole, 2009) However, they are different among regions, aquaculture practice systems, time, size and changeability (De Silva & Soto, 2009) Some studies in Southeast Asian countries included the poverty, marginalization and lack of alternative incomes that make fishery communities unable to cope with the impact of climate change in Cambodia (Baran, Schwartz & Kura, 2009), the disease and virus outbreaks led to decrease the profits of aquaculture activities in Thailand (Flaherty, Vandergeest& Miller, 1999), the performance of aquaculture production

under the environmental pressure of climate change in Malaysia (Hamdan et al.,

2015) In Vietnam, the storm surges, sea level rise, high waves and strong winds had caused severe damages and losses to aquaculture production (Kelly & Adger, 1999), the frequent flood events had caused loose to a huge number of fish and shrimps production in Red River Delta, Central Region and Mekong Delta (Asian Development Bank [ADB], 2009)

Due to the remarkable contribution of aquaculture production towards economic growth, the concerns about environmental externalities and consequences related to sustainability of aquaculture activities have been increasing during recent years (Tisdell & Leung, 1999) Fluctuation of climate events such as changing water temperature and annual precipitation, the shift of raining and dry seasons all changes the physiological, ecological and operational aspects of aquaculture activities

(Handisyde et al., 2006) Especially, changes in temperature and precipitation may

lead to a rise in the occurrence of some kinds of virus, bacteria and parasites in water sources (Siwar, Alam, Murad and Al-Amin, 2009; Handisyde et al., 2006) It is hard to predict and identify the causes of disease outbreaks and increasing mortality risks in relation to aquaculture production

In order to minimize the impacts from external environmental factors as well as from fish farms to the environment, applying recirculation aquaculture technology could be considered for a greater commercial scale providing for the development of

aquaculture production, profitability and environmental sustainability (Timmons et al.,

2007) The study “Comparison of water quality and production performance of

barramundi (Lates calcarifer) fingerlings in two systems: a recirculation system

and a flow-through system” was conducted as a pioneer model of application new

technology in barramundi fish farming in Viet Nam, especially in the context of climate change

The study focuses on barramundi fingerlings in the nursery phase This stage plays a decisive role for the final output because small fish are easy to be infected with disease and get high mortality The system was analyzed for a nursery with a single-batch, reaching a desired 30 g fish size in 40 – 50 days before harvested Survival data of fish and water quality parameters were collected and monitored as indicators of the system performance

Specific objectives are to:

1) Evaluate the important environmental parameters of the recirculation system for commercial fish farm in nursery phase, compared with the flow-through system in the same facilities;

2) Compare the efficiency of barramundi production between the RAS and the FTS in the nursery phase;

3) Preliminary assessment of investment costs for two systems: RAS and FTS

Chapter 2: LITERATURE REVIEW 2.1 Recirculation aquaculture system

RAS is closed culture systems with less water change or zero-discharge, intensive, usually indoor tank-based systems that achieve high rates of water re-use by mechanical, biological chemical filtration and other treatment steps Normally, the mechanical stage removes the solid waste, the biological filtration removes the dissolved wastes and converts the ammonia to nitrate, and sterilization subsequently reduces the bacterial and pathogen concentration in the entire system (Figure 2.1)

Figure 2.1: Schematic diagram of a basic RAS

More recently, the addition of a denitrification stage has shown potential in

increasing the volume of water recycled and decreasing waste outputs (Steicke et al.,

2009) In fact, most recirculation technologies are being applied in aquaculture today need a replacement of 10 – 20% of water used per day (Timmons and Ebeling, 2012) Dissolved oxygen (DO), carbon dioxide, ammonia, nitrite, nitrate are the critical water quality variables in RAS that may affect fish health as well as result of production

(Colt et al., 2006) With recirculation technology, an operator can secure greater

control over the environmental parameters and water quality, give less stress and better

growth, thus enabling optimal conditions for fish culture (Heinen et al., 1996; Badiola

et al., 2012; Carrera et al., 2013) Basically, RAS has a unit for growing fish, a

mechanical filter to remove larger particles before bio-filtration, an aerobic biological

nitrification area to remove potentially toxic nitrogenous compounds and sometimes

an anaerobic denitrification filter (Barbu et al., 2008)

RAS can be considered as an opportunity to reduce water consumption and effluent emission by a factor of 100 in comparison to traditional FTS (Blancheton, 2000) and allow concomitant control of rearing water quality In RAS, the make-up water needs, about 1 m3 per kg of feed, are 100 times lower than in FTS (Mac Millan,

1992; Blancheton et al., 2007) Besides, RAS can reduce potential environmental

impacts by increasing feed conversion (Fredricks, K.T., 2015) The lower exchange rate in RAS also allows for controlling temperature, which creates the best conditions for year-round production (Gutierrez-Wing and Malone, 2006; Lyssenko and Wheaton, 2006) and reduces energy costs whilst maintaining a particular

water-temperature (Summerfelt et al., 2001; Avnimelech, 2006; Gutierrez-Wing and Malone,

2006) RAS also allows for better bio-security and independence in location of

production facilities (Summerfelt et al., 2001; Cancino-Madariaga et al., 2011)

Finally, RAS allows for higher output and a higher density of fish per unit of

production tanks (Lyssenko and Wheaton, 2006; Good et al.,2009; Gullian-Klanian

and Arámburu-Adame, 2013)

Figure 2.2: A RAS compared with a traditional FTS

(Source: Lekang, Odd-Ivar, 2013)

Due to the possibility to maintain a constant water quality, RAS may also contribute to improve growth performance, feed conversion ratio (FCR) and survival rate of aquatic animals RAS production has increased significantly in volume and species diversity since the late of 80’s (Rosenthal, 1980; Verreth and Eding, 1993;

Martins et al., 2005) Today, more than 10 species are produced in RAS facilities

(African catfish, tilapia, eel and trout as major freshwater species and salmon, rainbow

trout, turbot, sea-bass and sole as major marine species) (Martins et al., 2010)

Despite the many advantages of using recirculation technology in fish farming, the operation of RAS requires a mechanically sophisticated and biologically complex

system (Duning et al 1998) To control this system, managers and farmers have good

knowledge of the design of the system, specification of the technical components and operation of it Although RAS technology is considered to have environmentally friendly characteristics and demonstrates an increasing number of applications in European countries, its contribution to production is still small compared to sea cages,

ponds or FTS (Martins et al., 2010) Besides, the high initial capital investment does in part lead to slow adoption of RAS technology (Schneider et al., 2006) High stocking

densities and production are required to be able to cover investment costs

Literatures on RAS are still limited and mostly focuses on technical issues or stocking densities at experimental scales Some authors have reported about water quality assessment and fish performance in recirculation systems for some species

productions, such as Arctic charr Salvelinus alpines L in Iceland (Molleda, 2007), Rainbow trout Oncorhynchusmykiss and European sea bass Dicentrarchuslabrax in France (Blancheton et al., 2009), Nile Tilapia Oreochromisniloticus in Mexico (Gullian-Klanian and Arámburu-Adame, 2013), Salmonid in Czech Republic (Buric et

al., 2014) The evaluation of water quality and performance of Barramundi (Lates calcarifer) in RAS has not been studied to a significant level yet, particularly at the

commercial fish farming A combination of environmental parameters such as DO

(Wajsbrot et al., 1991; Foss et al., 2003), salinity (Alabaster et al., 1979; Sampaio et

ammonia may cause fish health problems Classical production parameters, such as

growth and survival rates (Jørgensen et al., 1993; Canario et al., 1998; Papoutsoglou et

al., 1998; Irwin et al., 1999; Sørum and Damsgård, 2004) can be used to assess fish

performance Research conducted at a Barramundi farming documenting potential benefits of applying RAS can help producers get more relevant information to select the appropriate system with production scale and specific culture species

2.2 Barramundi, distribution and production

Barramundi is the accepted common name used in Australia, but the fish is also known under others names in different countries, but often more generally as Asian

sea-bass or Lates calcarifer (Bloch, 1790) in the literatures Barramundi is a

euryhaline member of the family Centropomidae (Katayama, 1956; Grey, D L 1987,

Tucker et al., 2002), can be grown in salinities ranging from fresh to sea water (0 – 36

‰) Available information shows that juvenile barramundi tends to grow faster in lower salinities The optimum temperature for growth of this species is between 280C and 320C According to Meynecke et al., 2013, higher temperatures can enhance

primary production and increase growth rates as well as fish activity The species is widely distributed in the Indo-West Pacific region from the Arabian Gulf to China, Taiwan, Papua New Guinea and northern Australia (Figure 2.3)

Figure 2.3: Distribution map for Lates calcarifer

Aquaculture of this species commenced in the early 1970s in Thailand and rapidly expanded to China, India, Indonesia, Malaysia, the Philippines, Singapore, Taiwan, Vietnam and Australia More recently countries such as the United States of America, the Netherlands, the United Kingdom and Israel have also developed

barramundi farming (Glenn Schipp et al., 2007) The popularity and demand for

barramundi made it a potential candidate for aquaculture It also has some characteristics like tender, mild tasting, boneless fillets and rich omega-3 fatty acids that endear it to the consumers

Figure 2.4: Main producer countries of Lates calcarifer

(Source: FAO, 2006)

According to FAO Fishery statistics, annual barramundi production has been quite stable since 1998, around 20 – 27 thousand tons, then, continuously increased in subsequent years, particularly from 2008 onwards The highest yield was achieved over 77 thousand tons in 2012 Thailand is the largest producer with about 8 thousand tons per year from 2001 Indonesia, Malaysia and Taiwan are also the substantial producers There has been a significant increase of international production of barramundi in the last few years, mainly from Vietnam, Thailand and China Because

of the differences in the consumption demand of barramundi in these countries,

various levels of production and culture technologies also exist (Ayson et al., 2013)

Barramundi is also successfully cultured in commercial farms in all Australian

mainland states and the Northern Territory (Harrison et al., 2013) Producers have

used land based ponds and raceways, open ocean sea cages, and recirculation aquaculture systems in their farms Recently years, the innovation and technological advances have fuelled the growth of the Australian farmed barramundi industry, as

according to Harrison et al., 2013 wrote “industry production statistics in Australia do

not account for the commercial value of seed stock supply, but advancements in this area certainly underpin the growth that this industry has enjoyed recently and is likely

to further fuel growth in the future” Highly intensive shore-based grow out aquaculture systems combined with a year-round supply of hatchery produced fish is

currently practiced in a number of Australian states (Meynecke et al., 2013)

Figure 2.5: Global aquaculture production for Lates calcarifer

(Source: FAO, 2014)

2.3 Nursery phase

The nursery phase can be defined as the growth period between 20 mm and 100

- 120 mm in length, it is also one of the most important steps for seed propagation in

the grow-out phase (Maneewong, S et al., 1981) This is also considered the most

difficult phase of barramundi culture because cannibalism is usually more intense

during this period than during later stages of culture (Parazo et al., 1991) Barramundi

are weaned from a live food diet onto formulated feeds and grown in tanks to reach

100 mm total length (Glenn Schipp et al., 2007) In order to avoid high mortalities and

maintain high production at this stage, many factors must be considered, including water quality, type of feeds and feeding schedule, stocking densities, grading and diseases

Today, most nurseries around the world use an intensive nursery system where the fish are kept at high densities, fed formulated feed and graded regularly to control

cannibalism and improve growth rates (Glenn Schipp et al., 2007) The nursing period

lasts about 40 – 50 days until fish reach 100 mm of total length or about 30 g of body weight After this stage, fish can be stronger and are moved to acclimation system with sea water before transferred to grow-out sea cages

Chapter 3: MATERIALS AND METHOD

3.1 Study site

The study was conducted at Australis Aquaculture Viet Nam Ltd (AAV), facilities which are located in Ninh Hai commune, Ninh Hoa town, Khanh Hoa province AAV has developed Barramundi fish farming at an industrial scale since

2007 They have hatched and reared Barramundi fingerling in land-based tanks and complete the grow-out process in modern sea cages Annual yield reached two thousand tons (2014)

The nursery was designed around the need to regularly grade the fish to control cannibalism with 12 small circular indoor tanks with a volume of 8 m3, flow rate of 150L.minutes- and 2 big circular tanks with a volume of 50 m3, flow rate of 300 L.minutes- All tanks are made of fiberglass reinforced plastic (FRP)

Figure 3.1: Small tanks in AAV nursery

The data on FTS in the nursery phase was gathered from October 2014 to September 2015 Water was continuously pumped (Ebara, Italia) from the sea through the baffle filter (38 m x 2.4 m x 1.8 m) to the drum filter (Ohex, Denmark) and came the culture tanks The circular tanks were set up with new sea water flowing through at

hour respectively for big tanks Water temperature depended on environmental conditions and salinity oscillated around 30 – 34‰

From October 2015 to September 2016, RAS has replaced the FTS in the same facility Instead of directly pumping water from the sea, water was continuously recirculated from the rearing tanks through the up-weller and the drum filter, next to the biological filter, degassing box and then went through to UV light before back to the rearing tanks (Figure 2.2) The total water volume of the system is 196 m3 and 20 – 30% of the system water is exchanged with new water to dilute the high level of ammonia and nitrites The salinity was 15‰, be reused throughout the system and water temperature was maintained above 280C using a heat pump

Figure 3.2: A schematic design of the basic components of AAV nursery

Liquid oxygen was used to increase stocking densities and efficiency of operation in both FTS and RAS These high stocking densities could be achieved using high water exchange in the FTS and oxygenation delivered to the tanks via bio-weave diffusers The same commercial pellet containing 55% crude protein and 5000 kcal.kg-(Ocialis, INVIVO NSA – France) was used until the fish reached 30 g of body weight (BW) After that, fish were moved to acclimation system for few days before transferring to sea cage Actual data on the FTS and the RAS at this facility and some other data on commercial scale barramundi for this thesis work were collected under the guidance of Mr Daniel Mark Fisk – Managing Director of AAV

3.2 Production setup

The general protocols for all stocking fingerlings include checking fish health before moving to nursery farm and the results were free with pathogens (virus, bacteria and parasites) At the FTS, 300,000 barramundi fingerlings (2.0 ± 0.15 g) were stocked

at 8 kg.m-3 in small tanks, fed 4 times a day for 48 days In the meanwhile, 400,000 barramundi fingerlingsof the same size were stocked at 20 kg.m-3 in small tanks, fed 3 times a day during 40 – 50 days in the RAS The maximum stocking densities in FTS and RAS was 40 kg.m-3 and 66 kg.m-3, respectively With these facilities, the FTS and the RAS could produce approximately 1.8 million and more than 2.5 million fingerlings a year, respectively

All fish in the FTS and the RAS were injected with Irrido V and Strep Si vaccines at

10 g of average weight The same chemical treatment and handling protocols were applied in both systems The various production parameters include survival rate, feeding rate, growth rate which were recorded and managed every day till the fish are ready for transfer to sea cages for grow-out farm

3.3 Water quality

Concentrations of dissolved oxygen (DO), temperature, un-ionized nitrogen, nitrite-nitrogen and carbon dioxide in the water of the culture system are the critical environmental parameters Besides nitrate concentration, pH and alkalinity levels within the system are also important factors If aquaculture systems are maintained good water quality during periods of fish growth, fish production can get

ammonia-Table 3.1: Environmental parameters

Parameters Measuring method/Tool In RAS In FTS

DO Oxyguard/ In-situ probes 6 times a day 6 times a day

Temperature Oxyguard/ In-situ probes 6 times a day 6 times a day

NH4+ Sera Test At 8.00 am, 4.00 pm At 8.00 am, 4.00 pm

CO2 Oxyguard CO2 portable analyser At 8.00 am, 4.00 pm N/A

Total bacteria Cultured on TSA media At 8.00 am At 8.00 am

Vibrio Cultured on TCBS media At 8.00 am At 8.00 am

In both the FTS and the RAS, water temperature and DO were monitored at least six times a day after feeding in each tank using Oxyguard® probes and In-situ probes connected to an Apple Ipod or a computerized measuring system (Linde soft) (Figure 3.3)

Figure 3.3: Oxygen meters in AAV nursery

The same daily measurements of pH, ammonium (NH4

+

), nitrite (NO2

-) and nitrate (NO3

-) were also taken in the FTS and the RAS The pH was measured with a

pH meter (Trans-instruments, Singapore) Total ammonium (NH4

+

), nitrite (NO2

-), nitrate (NO3

-) were determined using test kits (Sera Test, Germany-) Then, the concentration of unionized ammonia nitrogen (NH3-N) was calculated using the Johansson and Wedborg (1980) equation according to pH and temperature values Carbon dioxide gas (CO2), alkalinity, hardness and total suspended solid (TSS) were daily measured in the RAS to ensure maintaining the good water quality for the system These parameters were not daily monitored in the FTS The CO2 was measured with a CO2 meter (Oxyguard® CO2portable analyser) Alkalinity and hardness were determined by test kits (Sera Test, Germany) TSS concentrations were determined by method of total solids dried at 103 – 1050C (APHA, 1975 Method 208D) Calculating TSS by using the equation below:

Where: m2 is the post weight of the filter, m1 is the pre weight of the filter and V