This document provides information on cage culture, including its history, benefits, risks, principles, and an example of pangasius cage culture in Vietnam. Cage culture started in the 1950s and has since spread worldwide. It provides benefits like high stocking densities and yields but also risks like disease outbreaks and environmental pollution. Principles of cage culture involve proper site selection, cage design and structure, species selection, and water quality management. Pangasius cage culture is then described in detail covering its site selection, cage design, stocking, feeding, husbandry, disease management, harvesting, and profits.

1. CAGE CULTURE Nguyen Van Sang, MSc. nguyenvansang1973@yahoo.com Research Institute for Aquaculture No.2

2. Contents Review of cage culture Benefits, risks and disadvantages Principles of cage culture 3.1. Site selection 3.2. Cage structure and design 3.3. Culture species Example of pangasius cage culture 4.1. Site selection 4.2. Cage design 4.3. Stocking 4.4. Feeds and feeding 4.5. Husbandry and management 4.6. Harvesting & marketting 4.7. Profits

3. 1. Review of cage culture World cage culture Started in 1950’s in Thailand and Indonesia, 1960’s in Japan and Cambidia, 1970’s in Europe and USA, and 1980’s in Africa Cage can be placed pond, reservoir, canal, river and seashore. Cage made from bamboo, wood, polyetylene or metal net. Modern cage is now well equiped. Yield can reach to 200 kg/m 3 Vietnam cage culture Started in South Vietnam in 1958 and later spread to other parts of the country, firstly in freshwater body and later to seashore. Cage can be placed reservoir, canal, river and seashore. Cage made from bamboo, wood, polyetylene or metal net. 2009: 3.432 sea cages; larger number for freshwater cages Yield can reach to 150 kg/m 3

4. 2. Benefits, risks and disadvantages Benefit Occupy a small area of river, canal or seashore Cage can be made from available and cheap materials Poor farmers can manage small cage culture Fish can be stocked with high density, fast growth Yield and profit are high Easy to manage and harvest.

5. Risk and disadvantages Disease outbreak is common because of high density, contamination from other farms and quick changes of environment. Can cause environment polution in the long run because waste and nutrients can not be treated and discharged directly to water body. Culture cycle depends much on season and culture cage is affected by floods, torms and strong wave,… In some case, cages become obstacles for transportation and landscape

6. 3. Principles of cage culture

7. 3.1. Site selection Water depth: At least 5 meters, from lowest level or tide To ensure cage bottom-bottom of water body: 2-3 meters Water current, wave and wind Avoid strong wind, wave and current Marine: bay Fresh: river, canal, reservoir Current River and reservoir: 20-50 cm/s Sea: below 75 cm/s Wave: lower 2 meters

8. Khanh Hoa

9. Bad site (Strong Wave)

10. Use only good quality material, available, cheap, and has long-term economic value. The size of raft is not too big (10x10 m), so that easy to move if necessary. Using anchor and other things that cannot be rusty, with limited number, and placed in certain area that can not harm the environment/coral. Buoy can be made from Styrofoam, plastic drum; plastic drum is injected by Styrofoam. Design and lay out of floating net cages is made to make easier operational Design and lay out of floating net cages Design and lay out of floating net cages is need to consider several variables : CONDITION IN TANJUNG PUTUS Pond culture Pond Unit lay out not regulated nicely

11. Cage culture in Vung Tau province, Vietnam Too crowded Inhabitant zone Pond shrimp culture Estuary zone

12. Culrure area Fishing ship Inhabitant zones Inhabitant zones Nha Trang

13. Water quality DO: 4-6 mg/l Temperature: 25-30 0 C Salinity: Sea cage: 27-33% 0 Fresh water cage: depends on species pH: 6.5-8.5 NH 3 -N : 0.5mg/l (fresh) and 0,1mg/l (marine)

14. Others River/canal wide, distance from river bank to cage, between cages: depends on regulation? Far from discharge from agriculture activities, crowd inhabitants, industrial areas, ports Far from estuary, gate of canal or bendy part of river or canal: bring high effluents and nutrients Sandy bottom is preferred: Avoid acidic and red tide water Far from other cages (certain buffer zone, carrying capacity) Easy transportation, available electricity, near fingerling and feed sources, and market Check all above conditions before setting cages

15. 3.2. Cage structure and design Cage type: 3 types: floating , surface fixed and bottom cages; Materials: Frame and wall: Can be bamboo, wood, zinc coated iron, stainless steel, aluminum, fiberglass Number of bars for frame and wall depends on the size of cage Buoys Can be bamboo, plastic barrel, oil drum, sponge Number of these buoys depends on the size and structure of cage Net Metal, knotless polyetylene, polyamide Weight to fix net bottom Fixing cage: Anchor: iron , concrete Anchor rope: Others: airpump, electric generator, water compressor, feeder, excess feed counter, camera, feeding frame, connecting bridge, boat, house + office

18. Buoy (200L) Two bar of wood (0,3m) 6m 6m b. Design of draft of floating net cage 0.5-1m Storehouse Lab Accomod-ation Living room Cleaning area

20. Anchor Fig. 7Cage design for marine fish rearing and growout

21. Cage design Shape: rectangular: single or group, circular, hexagon Size: several m 3 to hundreds m 3 Rectangular: Area: 3mx2m ÷ 10mx20m Depth: 1.5m ÷ 4.5m Circular: stand strong wind, huge wave and strong current Diameter: 25mx35m Depth: 40m Mesh net: Depends on size of fish stocked, 2a=1.5-5.0 cm Normally don’t change during culture cycle

22. Example for mesh size of cobia cage culture Fish weight (g) Cage size (m) Mesh size (cm) < 50 2 x 2 x 2 0.5 50-500 3 x 3 x 3 1-2 500-2000 4 x 4 x 3 2-3 2000-4000 6x6x3 4-5 4000-6000 12x6x4 5-7 > 6000 12x6x4 7-10

23. Make a floating wooden cage installed in river Wood and bamboo are well dried Good quality woods are used. Woods are polished before used. Cage side: wood Bar surface of 10cm x 20 cm or 4cm x 6cm normally use for large or small cages Wooden bar interval is smaller than the size of fish Cage front & back: mesh net, can use smaller mesh net or plastic bag to reduce water current Cage bottom: wooden, close bottom Top of cage: wooden bar or bamboo, leave some feeding doors Buoy: to ensure cage floating and stand for weight of human and equipments

24. Example of a modern cage in Norway Circular cage Frame made from 2-3 polyetylene pipes, surface and bottom pipes connected by polyetylene stand. Size: 25-35m in diameter; depth: 40 meters Equiped with computer program for feeding and management: airpump feeder, excess feed collector, fish behaviour/health. 3 sites, 6 km in between, one site resting for one cycle

26. 3.3. Culture species Fresh water: tilapia (GIFT and red), carp, grass carp, snakehead, pangasius ( P. hypophthalmus, P. bocourti ),… Marine: grouper, cobia, lobster, red snapper, sea bream, greater amberjack,…

29. 4. Pangasius cage culture 4.1. Site selection River/canal or reservoir: freshwater and salinity below 10% 0 Current: 0.1-0.6 m/s pH: 7.0-7.5 DO: 4.3-9.7 mg/l Meet other criteria mention in 3.1.

30. 4.2. Cage design Cage type: floating bamboo or wooden cage Cage wall: Can be bamboo; wood; metal; knotless polyetylene and polyamide nets Others: feeding frame, connecting bridge, house + office

31. 4.3 Stocking - Fingerling sources: + Artificial propagation source - Size & stocking density: + 60-80 g/fish + Density: 100-250 inds/m 3 - Mono or polyculture? + Normally monoculture + Polyculture in some case, example: 5-10% of carps ( Puntius altus ) - Season + Stock fingerling when flooding season is over and harvest before new season comes

32. 4.4. Feeds and feeding Kinds of feeds Home made feed: mixture of different ingredients Commercial pellet feed Feed composition Ingredients: Fish meal, soybean meal, rice bran, broken rice, agglutinative substance , vitamins and minerals. Composition: 20-28% protein, 40-50% carbonhydrate, 8-11% lipids, 16-22% ash Feed preparation Home made feed: cooked and then vitamins and minerials added. Commercial pellet feeds: uncooked, vitamins and minerials added.

33. - Feeding + Frequency: 2-4 times/day + Feed size: 2-10 cm depends on size of fish + Feeding duration: 30-60’ + Feeding space: wide enough

34. 3 5 300-500 3 3-5 >500 5 5 100-300 5-7 6-12 <100 % body weight % body weight Size of fish (g) Commercial pellets Home made feed

35. - FCR + Trash fish/mixture: 3.0-3.5 + Commercial pellets: 1.5-1.7 - Growth rate + 1-5 g/day

36. 4.5. Husbandry and management Fingerling: uniform in size, healthy Appropiate transportation and treatment: e.g. 3% NaCL Water quality check Parameters: curent, temperature, pH, DO, transparency, salinity, NH 3 -N, BOD, COD Action: Water ventilation/aeration Changing cage position in order to meet required current and quality Hanging lime and/or salt in front of cage Fish health Check: Behaviour & clinical sign Determine causes Action To reduce or stop feeding accordingly To remove dead, weak and infected fish in time Disease treatment by supplying chemicals and drugs in water and feeds

37. Common diseases: Fungi: Skin: Saprolegnia, Fusarium sp Parasites: Gill: dactylogyrus; Skin: sporozoan, trichodina Intestine: Philometra

38. Bacteria Red spot: Aeromonas hydrophila and Pseudomonas fluoresen Instestine haemorrhage: Enterococcus White spot disease : Edwardsiella ictaluri White gill & liver

39. Oxygenation, water current and wave Supply oxygen when there is no water current, high nutrient water, disease treatment (airpump, ventilator). Reduce water current and wave by changing cage position. Sorting and lower density: Remove smaller size to other cage and harvest the bigger fish. Lower density in some cases

40. Cleaning and disinfection: before stocking and during grow-out cycle Net, frame: brush and chemical Bottom: flow sediments (waste, silt), frequently: 1-4 times/month Surface: daily Net tear, predator, cage fixing,… Net tear and predator check: regularly Checking regularly spoiled bouys, frame, bottom and surface to replace on time: weekly Change cage position: Appropiate current, depth Tighten cage by installing more anchor ropes during flood and strong wave. Change net: normally do during resting period

41. 4.6. Harvesting and selling Market size: 0.8-1.0 kg Yield: 80-220 kg/m 3 Quality 95% white meat

42. Harvest method: Multi-harvest & single harvest Live fish: preferred Well-boat Small boat: some ice Container by cool truck Dead icy fish

43. 4.7. Profit ( Tilapia in 2005 ) 53.6 55.1 55.1 55.2 54.7 55.2 43.0 57.0 Profit ratio (profit*100/investment) (%) 4.5 4.79 4.80 4.80 4.76 4.80 4.2 3.4 Profit ratio (Million VND/tons) 55.1 61.4 78.6 54.7 53.7 53.3 60.5 53.3 Yield (kg/m 3 ) 66.1 57.7 48.7 69.4 58.4 62.7 85 81 Survival rate (%) 0.59 0.62 0.72 0.50 0.70 0.57 0.43 0.61 Mean weight (kg) Aver. 7 6 5 4 3 2 1 Exmaple of tilapia: 15.000 VND/USD

44. Thank you very much for your attention!