Đề tài Intensive in-Pond raceway production of marine finfish (card vie 062-04) - milestone 2& 4 report

Ministry of Agriculture & Rural Development Project Progress Report Project title: INTENSIVE IN-POND RACEWAY PRODUCTION OF MARINE FINFISH (CARD VIE 062/04) MILESTONE 2& 4 REPORT Two milestone reports are combined in one for ease in understanding of raceway technology and application of potential users Michael Burke (QDPI&F, Australia) Tung Hoang (Nha Trang University, Vietnam) 12/2006 PART 1 Design and performance of floating raceways used to nurse fingerlings of marine finfish in Central Vietnam 1 Design and performance of floating raceways used to nurse fingerlings of marine finfish in Central Vietnam Tung Hoang1*, Phuong T. Luu1, Khanh K. Huynh2, Quyen Q.T. Banh1, Mao D. Nguyen1, Michael Burke3 1 International Center for Training and Research, Nha Trang University, Vietnam 2 Khanh Hoa Fisheries Promotion Center, Vietnam 3 Department of Primary Industries & Fisheries, Bribie Island Aquaculture Research Centre, Bribie Island, Queensland, Australia 1. INTRODUCTION The development of mariculture in Vietnam requires large number of marine fish fingerlings for stocking. In recent years, small seeds of high-value fish such as grouper (Epinephelus spp.), cobia (Rachycentron canadum), barramundi (Lates calcarifer) and other species are produced in hatcheries, meeting part of the increasing demand by fish farmers. Not only quantity, but also body size of fingerlings is limited. Marine finfish are mostly cultured in cages in Vietnam. Stocking, therefore, requires fingerlings larger than 80÷100 mm in total length. In hatcheries, the production of large fingerling is costly and apparently constrained by limited nursing tank area. Poor survival and difficult husbandry are recorded also with nursing in ponds (Le Xan 2005). Floating raceways have been recently trialled successfully for freshwater fish farming in USA, Australia and Germany. Despite of their relatively high capital and running costs, the use of floating raceways has a number of advantages including (i) high stocking density and less predation; (ii) effective feeding and disease management; (iii) easy to handle and fewer labor required; (iv) taking advantage of natural food in ponds. In Vietnam, Nha Trang University (the former University of Fisheries) designed a floating raceway and trialled this system in 2005 – 2006 through the CARD VIE 062/04 project “Intensive in-pond raceway production of marine finfish” coordinated by the Ministry of Agriculture and Rural Development of Vietnam. This current report presents the working principles of floating raceways; guidelines for installation and operation of the version SMART–1 for nursing marine finfish fingerlings; experimental results on barramundi (Lates calcarifer) covering both financial assessment and dynamics of raceways. Some initial results on snapper (Lutjanus argentimacus), red drum and red tilapia (Oreochromis sp.) are also discussed. Target species for coming trials are cobia and grouper. 2 2. DESIGN OF FLOATING RACEWAY 2.1 Operational principles Operational principles of floating raceway (FR) is relatively simple. FR can be made of different materials and looks like a long, narrow tank that float itself or supported by floating structure. Water in reservoir pond is continuously pumped into one end and discharged at the other end of the raceway through a system of airlifts, powered by central air compressor or blower. This helps reduce power costs and increase dissolved oxygen concentration. Fish are nursed or grown in raceways at high densities, fed with formulated feed. In addition, plankton in reservoir pond is an important supplementary feed source for small fish. To keep fish from escaping, a screen is installed at the outlet of raceways. Net is also used to cover the raceway’s surface to protect fish from predation. Floating raceways should be designed to maintain high exchange rate, enable waste collection and create a quiet area for feeding. In case chemical treatment is needed, raceways become ‘close’ tanks when the airlift operation is ceased and its outlet is blocked. Depending on biological requirement of the cultured species, floating raceways can be put in relatively deep pond containing either fresh, brackish or marine water. Reservoirs have enormous potentiality for the application of this farming system. However, electricity is required for operation of air compressor or blower. 2.2 Pond The rectangular reservoir pond is 2000 m2 (Fig. 1). Pond should be built on impermeable soil or lined with plastic. Pond bank is 1.5 slope and 1.8 – 2.0 m wide, making it convenient for daily management and harvesting. Pond bottom should be flat and inclines to outlets. The higher water level in pond, the better it is. Minimum water depth is 1.6 ÷ 1.7 m. Conversely, in case of low water levels, the airlift system will take up wastes and mud from pond bottom into raceways. The reservoir pond is partitioned by a plastic wall placed in the middle of the pond, directing water to flow around with the aid of a 2-hp paddle-wheel. 2.3 Floating raceways Floating raceways version SMART-01 are small in size, used to nurse marine finfish from small sizes to fingerlings. These are made of fiberglass – the most appropriate material in Vietnam which is durable, weather proof and easy to clean or move around. Despite its higher cost than other simple materials, fiberglass raceways have demonstrated a worthy investment. SMART-1 has a trapezoid-shape (3.5m3 volume, 3.5×0.8×1.0m), 30o 3 slopped at both heads (Fig. 2). One head of the raceway is connected with an airlift system. The other is attached with a screen to avoid fish escape and predators. At the inlet side of the raceway, a panel is put to drive water downwards. Overpass Floating raceways Sluice Air pipeline Air compressor Wall Aerator 1.8 – 2 m 1.8 m Bank Wall b Figure 1: Pond and in-pond floating raceways 2.4 Airlifts The airlift s ncludes four PVC ∅90-mm pipes. Each pipe is 100 cm long, attached togethe raceway. This fra side of this fram Air flow is contr on the lower side push water up. capacity” of the a 2.5 Air comp Water is pum upon the numbe six floating racew ystem ir by a rectangular frame made me also has a function of bringin e is connected with an air compr olled by a plastic valve. Four sma of the supporting frame, one for The distance from water surfac irlifts is dependent upon the pow ressor ped into the raceway by an air c r of airlifts and desired flow rate ays with a total of 24 airlifts) use 4of PVC ∅21-mm pipes, fixed into the g air into the airlifts (Fig. 3). The upper essor or a blower by a soft plastic pipe. ll holes (3.0 mm in diameter) are drilled each airlift, allowing air to flow in and e to these holes is 80 cm. “Pumping er of air compressor or blower used. ompressor whose capacity is dependent . The SMART-01 system (comprises of s an ANLET BSR-40 air compressor (3 HP or 2.2 KW; Made in Japan). The amount of compressed air is 66 m3 per hour. While operating, each airlift can pump about 86÷87 L of water per minute. 3.5 m 3.7 m 0.9m 0.6m 0.25m 2.5m Outlet Airlifts Inner side Outer side Hole to set airlift Groove to install baffleGroove to install screen Outlet a Figure 2: Structure of SMART-01 b Air Incoming water Coming-out water Air vent Figure 3: Structure of airlift system In order to ensu fficient dissolved oxygen and well prepare technical failure, two air compressors are used in turn. Each operates for 12 hours per day. The air line that connects the air compressor and the airlift system is designed to end as a rectangular loop around the su rting pontoon. This helps equalize the amount and pressure of compressed air at all positions in the system, allowing all the a operate at the same rate. 5irliftsd forre suppo 2.6 Supporting pontoon A pontoon is used to support the floating raceways. This system was constructed using 6×12 cm blocks of wood and 200-L HDPE drums. These materials are locally available and often used to make spiny rock lobster cages. The pontoon is rectangular in shape (510 × 750 cm) and is divided into six chambers. The width of each chamber is 95 cm, enabling convenience while lifting or lowering the floating raceways. Side walkway was made around the pontoon for daily management and husbandry practices (Fig. 4). The SMART- 01 system uses 17 HDPE drums arranged equally to support the pontoon, sufficiently enabling the attached raceways always float on the water surface when technicians are feeding the fish or cleaning the raceways. Six raceways are hung on the raft by Ø14 mm bolts (450 mm long). This helps keep the raceways emerged 5÷10 from the water surface Nonetheless, as the raceways are attached to the pontoon, their floatability is dependent upon the pontoon’s floatability. a’c c’ 6 1 2 1 b b’ 3 cross section topdown a 6 6 5 3 4 outflow side Inflow side Figure 4: Structure of floating raft supporting raceways Notes: 1: Floating raceways 2: Float 3: Airlifts 4: Outlet Screen 5: Bolds hanging raceways 6: Air supply 2.7 Installation and operation Firstly, the supporting pontoon is assembled and put into the reservoir pond. PVC and soft plastic pipes were then used to connect the air compressor with the raceways. When using PVC pipes, it is better to put them underground to prevent damage caused by UV ray and heat of sunshine. As the air coming off the compressor is very hot, the first segment of the pipe that attaches to the compressor must be heat-resistant or made of zinc, and is about 6 six meters long. Next, the raceways, airlifts and regulating valves are installed. The compressor ANLET BSR 40 is capable of operating six raceways and one separate air outlet for emergency use or when additional aeration in raceways is needed, e.g. during therapeutic treatment or harvesting. The top baffle, once installed will direct incoming flows downwards and velocity of surface current is nearly zero. This helps create a quiet area for feeding behind the baffle. In addition, the downwards flow will push faeces and uneaten feed toward the end of raceways. Part of this waste will overflow through the raceway’s outlet. The rest is accumulated at the end of the raceways and will be daily siphoned out. The newest system SMART-02 has a waste trap for ease in maintenance. Key environmental parameters such as salinity, pH, NH4-N, total dissolved solids (TDS) and temperature are equivalent between the raceways and the reservoir pond. Therefore, good control of water quality in pond will ensure good nursing environment in raceways. Thanks to the airlifts, dissolved oxygen levels of water in raceways well meet fish’s requirement. However, regular attention should be paid to the aeration system because, by any means, if this system ceases (e.g. due to no power or technical problems), fish mortality due to lack of oxygen is extremely high. When nursing species that need natural foods, fertilizers should be used to promote plankton growth in the reservoir pond. During operation, the aeration system must be regularly checked. As density of fingerlings in raceways is very high, any problem related to air loss is a danger to fish. Two air compressors should be used in turn to prolong longevity and minimize damages because of overwork. In geographical areas where electricity is not reliable, it is advisable to prepare a petrol-operated generator . Farmers can adjust the amount of air and number of airlift to control water exchange rate as well as velocity of current in raceways that best suit the cultured species. The airlifts will underperform if being bio-fouled. Thus, this system must be cleaned periodically. Cleaning raceways can be conducted easily by using brushing along the inner sides and bottom of raceways. However, when nursing species which is sensitive to turbulence like barramundi, it had better not clean raceways daily. 3. EVALUATING PERFORMANCE OF SMART-01 ON BARRAMUNDI 3.1 Experimental method Barramundi fingerlings (15÷20 mm total length) were locally produced and transported to the trial site at Ninh Loc, Khanh Hoa which is belong to the Khanh Hoa 7 Fisheries Extension Center. Stocking density was 10,000 fish per raceway or 3.3 fish/L. Two trials were conducted; each used three raceways. The raceways were chlorinated at 100 ppm before used. The total length and body weight of fish are determined after two- day acclimation. Fish were fed with INVE and Grobest pellet (granular size 800÷1200 µm; crude protein content 42÷56%). The former feed was used for younger stages in hatchery. In the first trial, fish were fed with INVE during the first week and then weaned to Grobest. In the second trial, fish were fed merely with Grobest pellet to reduce feed cost. The amount of feed is about 2÷18% of body weight depending on development stages and actual consumption. Fish were fed every hour 06:00 to 18:00. Feeding load was adjusted in the next feeding based on actual consumption of the current feeding. Key environmental parameters such as pH, dissolved oxygen (DO) and temperature were monitored daily at 08:00 and 14:00, both in raceways and in the reservoir pond. Other factors include total dissolved solids (TDS), total ammonium (NH3-N) and salinity were measured every five days; total suspended solid every 7 days. Sampling plankton at inlet and outlet of raceways, and in the reservoir pond was also conducted weekly to observe changes in species composition and evaluate “filtration efficiency” of the raceways. Artificial dye and small buoys were used to study the dynamics of water in the raceways. Every five days, 50 fish from each raceway were randomly collected. Total length and body weight were measured and recorded. Fish health was also assessed by visual examination. The survival rate was determined at the end of the experiments. The first trial lasted for three weeks and the second trial lasted for 5 weeks. The total length of the nursed fish was 60÷80 mm and 80÷100 mm, respectively at the end of the first and second trials. Survival, growth and size variation of nursed fish; profit margin and profit per unit of investment were used for overall assessment. 3.2 Operation of raceways and capacity of water exchange Flow rate from the reservoir pond to raceways is about 350 L/min. The use of artificial dye to estimate exchange rate revealed that water in raceways is completely exchanged every 15 mins (Fig. 1). This ensures relatively similar water quality between the in the reservoir pond and the raceways, except for DO and TSS (Table 1&2). DO of water in the raceways is always over 4.0 mg/L and higher than that in the reservoir pond through effective operation of the airlifts. TSS in raceway is higher than in pond due to accumulated faeces of fish and uneaten feed. 8 When operating without the top baffle, the average velocity of surface current is 35 cm/s. When the top baffle is used, the water flows downwards and aside with the bottom of the raceway. This forms a quiet area behind the top baffle for feeding and keep feed pellets in the raceway. Furthermore, suspended solids are brought out the raceway into pond more easily. Larger waste is accumulated at the end of raceway, making it easy for daily cleaning. Examination of the plankton samples showed that the diversity was similar between the raceways and in the reservoir pond. However, plankton biomass in raceway is higher than in pond (Table 1), demonstrating its plankton capturing efficiency. hút 2 - 3 phút 5 - 6 phút 7 - 8 phút 11 - 13 phút 15 - 20 phút T? ư?c Lư?i ch?nscreen? ng nâng nAirlifts m ch?nplate 0 p0 min Figure 5: Water exchange rates between raceways and pond (gray area indicates water mixed with artificial dye) Table 1 : Water quality in raceway and pond during the first trial. Data in the same rows with different superscripts are statically different (P < 0.05) Factors Pond Raceway 3 Raceway 4 Raceway 5 DO (ppm) Morning 3.95 ± 0.16a 4.55 ± 0.14b 4.54 ± 0.14b 4.60 ± 0.13b Afternoon 5.55 ± 0.17a 5.60 ± 0.16a 5.61 ± 0.17a 5.67 ± 0.16a Temperature (oC) Morning Afternoon pH Morning Afternoon Salinity (ppt) 31.6 ± 0.16a 31.6 ± 0.16a 31.6 ± 0.16a 31.6 ± 0.16a 33.4 ± 0.25a 33.3 ± 0.25a 33.3 ± 0.25a 33.3 ± 0.25a 7.6 ± 0.02a 7.6 ± 0.01a 7.6 ± 0.02a 7.6 ± 0.02a 7.6 ± 0.02a 7.6 ± 0.02a 7.6 ± 0.02a 7.6 ± 0.02a 22 ± 0.12a 22 ± 0.12a 22 ± 0.12a 22 ± 0.1a 9 Table 2 : Water quality in raceway and pond during the second trial. Data in the same rows with different superscripts are statically different (P < 0.05) Factors Pond Raceway 1 Raceway 2 Raceway 3 DO (ppm) Morning 5.85 ± 0.09a 5.86 ± 0.09a 5.80 ± 0.12a 5,80 ± 0,10a Afternoon 11.02 ± 0.24a 8.05 ± 0.20b 8.09 ± 0.21b 8,22 ± 0,21b Temperature (oC) Morning 30.2 ± 0.10a 30.1 ± 0.10a 30.1 ± 0.10a 30.1 ± 0,10a Afternoon 32.6 ± 0.30a 31.1 ± 0.20b 31.1 ± 0.20b 31.1 ± 0.20b pH Morning 8.1 ± 0.01a 8.0 ± 0.02a 8.0 ± 0.02a 8.0 ± 0.02a Afternoon 8.4 ± 0.01a 8.3 ± 0.02b 8.3 ± 0.02b 8.3 ± 0.02b Salinity (ppt) 29 ± 0.30a 29 ± 0.30a 29 ± 0.30a 29 ± 0.30a TSS (ppm) 63.8 ± 8.93a 111.1 ± 19.77b 92.5 ± 14.88a 92.4 ± 13.33a TDS (ppm) 1309 ± 48.9a 1357 ± 57.5a 1334 ± 59.1a 1321 ± 71.0a NH4+ (ppm) 0.13 ± 0.01a 0.13 ± 0.01a 0.13 ± 0.01a 0.13 ± 0.01a Outflow water top baffle Screen Airlifts beh mor fish the ± 0 Coe tota with imp from Inflow water Figure 6: Dynamic of flows in pond 3.3 Growth rate of f Nursed barramundi in raceways grew fast. They fed avior while feeding and did not eat in the dark. Feeding ning and late afternoon. Stomach examination of the nu larger than 20 mm in total length hardly used zooplankto first trial, the average body weight and total length (± S.E .05 cm, respectively after 15 days of nursing. Surv fficient of variation was 23.8 ± 0.83 % in term of weigh l length. Estimated food conversion ratio (FCR) is 0.83 ± nursing barramundi in earthen ponds or concrete tank rovements. Another separate experiment showed that growth and s 20 mm to 80 mm are not different when fed with INVE 10ish actively, showed aggressive was most active in the early rsed barramundi showed that n (Luu The Phuong 2006). In .) was 2.36 ± 0.07 g and 5.13 ival rate was 81.9 ± 1.0%. t and 11.7 ± 0.28 % in term of 0.01 (Table 3). In comparison s, these results are significant urvival of barramundi nursed or Grobest pellets (Table 4). Nevertheless, the cost for Grobest pellet is only 1/5 of INVE pellets. The aim to reduce feed cost, however, was not successful in the second trial where Grobest pellets were merely used. As the fish got used to INVE feed in the hatcheries, they were not interested in Grobest pellets. Furthermore, water quality was lower than that for the first trial. Pond water had been kept for 10 months and salinity was higher (Table 3). Fish were infected with copepod parasites Caligus. Consequently, hydroperoxide (H2O2) at 150 ppm was used to treat fish in raceways for 20 – 30 mins. Although relatively effective, it was one of the reasons for slow growth and lower survival of fish in the second trial. The overall performance of the second trial was, therefore, inferior than the first one. As a result, fish growth was not high for the second trial. Specific growth rate of weight and length of fish are 4.66 ± 0.05 %/day and 1.44 ± 0.03 %/day in the first and the second trials, respectively. At the end of the trial, the average total length was 10.03 ± 0.23 cm; average b