Environmental impacts from feeds used in aquaculture systems in the vicinity of mekong river vietnam

ABSTRACT This study was conducted in My Hoa Hung village in Long Xuyen city, An Giang province, Mekong River in Vietnam during August to December 2007, to assess environmental impacts fr

ENVIRONMENTAL IMPACTS FROM FEEDS USED IN AQUACULTURE SYSTEMS IN THE VICINITY OF THE MEKONG

RIVER, VIETNAM

by

Chau Thi Da

A thesis submitted in partial fulfillment of the requirements for the

degree of Master of Science in Aquaculture and Aquatic Resources Management

Examination Committee: Dr Amararatne Yakupitiyage (Chairperson)

Dr Wenresti G Gallardo (Member)

Dr Hakan Berg (Member)

Dr Yang Yi (Member)

Nationality: Vietnam Previous Degree: Bachelor of Science in Agronomy

Cantho University, Vietnam Scholarship Donor: MOET, Vietnam - AIT Fellowship

Asian Institute of Technology School of Environment Resources and Development

Thailand May, 2007

ACKNOWLEDGEMENTS

I wish to extend my deepest gratitude to my advisor Dr Amararatne Yakupitiyage, for his valuable guidance and constant encouragement, great patience, suggestion and advise through out the study period Despite his exceptionally busy schedule, he spares his time and efforts in going through the research draft, making alterations and giving appropriate verbal correction The present shape of thesis would not have been possible without his extensive guidance and correction

I wish to express special appreciation and my sincere thans to Dr Wenresti G Gallardo, Dr Hakan Berg and Dr Yang Yi as members of examination committee for their

valuable guidance, constant encouragement, great patience, and valuable suggestions Thanks

are due to my wife, Ms Thai Huynh Phuong Lan, who showed me numerous ways to improve

my English expressions in this thesis

I am grateful to Ministry of Education and Training, Vietnam and An Giang University Vietnam for its awards of the Masters scholarship I also sincere thanks to

Dr Nguyen Thanh Phuong, Dr Truong Quoc Phu (Department of Aquaculture and Fisheries – Can Tho University, Vietnam) and Mr Nguyen Thanh Son, Mr Bui Xuan Thanh, Mr Nguyen Minh Du and my fellow students Mr Nguyen Long Doat Quoc, Mr Nguyen Minh Ngoc and

Mr Nguyen Ngoc Lan in Department of Agriculture & Natural Resource, An Giang University Vietnam) for their valuable help during this thesis

Last but not least, this work is dedicated to my parents and family members for their love, patience, encouragement and moral support to complete my study in AIT I would like to thank to all of my classmates for their support during this study

ABSTRACT

This study was conducted in My Hoa Hung village in Long Xuyen city, An Giang province, Mekong River in Vietnam during August to December 2007, to assess environmental impacts from feeds used in aquaculture systems such as intensive fish cages,

pens and ponds culture on and in the vicinity of Mekong River, Vietnam (e.g Pangasius

Hypopthalamus, Colossoma macropomum species) Moreover, the purpose of this study is to

investigate the effects of feeds in the intensive aquaculture systems towards water

environment The study was commenced by a field survey of twenty Pangasius

hypophthalmus cage farmers, 18 Pangasius hypophthalmus pond farmers, 20 Pangasius hypophthalmus pen farmers and 15 Colossoma macropomum cage farmers The survey

showed that the fish culture in An Giang province was developed and operated by farmer’s indigenous knowledge The fish density is quite high of 80-105 fish/m2 as compared with the optimum range of 30-60 fish/m2 There are three kinds of popular feeds such as homemade,

pellet and Pangasius waste used in this area The pellet feed is more effective in terms of

economic profit, less environmental pollution, better product quality and reduction in trash fishes from nature Among three of culture systems, pen culture has more economic benefits because this system is separate from other systems It is located in the alluvial grounds with high water turnover so that fish is not affected by disease transmission from other farms Water quality of the river is still in the limit for fish culture in three surveyed months of August, October and December Nitrogen and phosphorus concentrations of October are lowest because this time is the peak up of flooding season In this study the adverse effects of fish culture is not revealed clearly due to the survey carried out in the rainy season

Table of Contents CHAPTER TITLE PAGE

Acknowledgements iiAbstract iii

2.5 Fish culture systems in An Giang province, Mekong River in

Vietnam

7

2.8 Nutrient requirements of Pangasius hypopthalamus 14

2.10 Basic biology of Colossoma macropomum 17

3.4 Assessment and comparison of the different systems 29

3.6 Assessment of effluent and feed waste contribution 29

4 Results and Discussion: Survey of aquaculture systems in An Giang

province

34

4.4 Costs and return benefit analysis (1 US$ = 15,000 VND) 534.5 Strength (opportunity), constraints and environmental awareness 57

5 Results and Discussion: Assessments of contribution of feed waste used

in aquaculture systems and water quality parameters

60

5.2 Materials and methods 60

5.5 Amount of nitrogen (N) and phosphorous (P) in the waste loading from feeds used into the river

List of Tables

2.1 Estimated numbers of Pangasius hypophthalmus fry caught in the dais fishery in

2.2 Status of Pangasius hypophthalmus pond culture in An Giang province 10

3.2 Samplings were carried out on three seasons in area selected 26

4.2 The distribution (%) of educational level of fish farming managers in An Giang

province 38 4.3 Farming experience of fish managers in An Giang province (%) 38

4.5 Total water volumes and total area of aquaculture systems in An Giang province 44

4.6 Production season of Pangasius hypophthalmus in An Giang province 44

4.7 Stocking densities in aquaculture systems in An Giang Province 45

4.8 Ingredients of homemade feed for Pangasius hypophthalmus species and

4.9 The ratio % materials in homemade feed used by household’s fish cage 48

4.10 Ingredients of homemade feed used for Colossoma macropomum species and

4.11 Variable costs of production unit of aquaculture systems in An Giang province 54

4.13 The percentages (%) of name of buyer in Mekong Delta, in Vietnam 57

5.1 Water level water level Hmax (m) in Tan Chau district of An Giang province and

5.2 Water temperature (T0C) in aquaculture systems in three seasons 62

5.3 pH levels in three seasons of aquaculture systems in An Giang province 63

5.5 TSS in aquaculture systems in three seasons 65 5.6 Nitrite-N (NO2) and nitrate-N (NO3) in aquaculture systems in three seasons 66

5.8 Total nitrogen in aquaculture systems in three seasons 69 5.9 Fish yield (tons/crop/culture unit) and FCR in relation to feed and feeding level

5.10 Feed consumed and fish biomass in dry matter related to waste material uneaten

5.11 Fish carcasses (adult fish) and feeds compositions analysis 72 5.12 Amount nitrogen (N) and phosphorous (P) (tons) content in feed used, fish

biomass and waste material in uneaten feed in different culture systems 73

List of Figures

2.1 Aquaculture timeline for both cage and pond production in Vietnam 8

2.2 Annual production of cage culture in An Giang and Dong Thap provinces 9

2.3 Proportion of different catfish species in the Mekong Delta in cage production 9

2.4 Annual production of Pangasius hypophthalmus spp for export in the Mekong

3.1 Study Area Map of An Giang Province, Mekong Delta, Vietnam 20

3.2 Top view of sampling site at the Pangasius hypophthalmus cage and Pen

culture 28

3.4 General view of the field measurement at My Hoa Hung, Long Xuyen city, An

3.5 Mass balances for phosphorus and nitrogen load from cage and pen fish

farming 30

4.1 Average ages of fish farmer’s manager in An Giang province 37

4.2 Percentage gender distribution of fish farmer’s manager in An Giang province 37

4.3 Previous occupation of fish farm owner in An Giang province 39

4.4 Cages culture in An Giang province, Mekong River of Vietnam 40

4.5 Pen culture in An Giang province, Mekong River of Vietnam 42

4.6 Pond culture in An Giang province, Mekong River of Vietnam 43

4.7 Kinds of feed used in Pangasius hypophthalmus culture systems 46

4.8 The percentages of fish farming using different ingredients of homemade feed

4.9 The percentages of fish farming using different ingredients of pangasius waste

4.10 Diagram of feed processing for Pangasius hypophthalmus species 50

4.11 Diagram of feed processing for Colossoma macropomum species 50

4.13 Colossoma macropomum feed processing 51

4.14 The ratios of fish farming using the additives in homemade feed 52

4.15 Average initial instruction cost of fish culture systems in An Giang province 54

4.16 The structure of the marketing of channel of fish aquaculture in the Mekong

5.1 General comparison views of water quality parameters in Cages, Pens and

culture 60 5.2 General comparison views of water quality parameters in Ponds culture 60

5.3 Water temperatures in upstream and downstream of cages and pens culture

compared to pump-in and pump-out of ponds culture during three seasons 62 5.4 pH levels in upstream and downstream of cages and pens culture compared to

pump-in and pump-out of ponds culture during three seasons 63 5.5 DO in upstream and downstream of cages and pens culture compared to pump-

in and pump-out of ponds culture during three seasons 64 5.6 TSS in upstream and downstream of cages and pens culture compared to pump-

in and pump-out of ponds culture during three seasons 65 5.7 Nitrite-N (NO2; mg/L) concentrations in upstream and downstream of cages

and pen culture compared to pump-in and pump-out of ponds culture during

5.8 Nitrate concentrations at upstream and downstream of cages and pens culture

as compared with pump-in and pump-out of ponds culture during three seasons 67 5.9 Total nitrogen in upstream and downstream of cages and pens culture as

compared with pump-in and pump-out of ponds culture during three seasons 68 5.10 Phosphorous concentrations in upstream and downstream of cages and pens

culture as compared with pump-in and pump-out of ponds culture during three seasons 69

CHAPTER 1

INTRODUCTION 1.1 Introduction

In recent years, aquaculture production has increased worldwide, mainly due to the increasing demand for aquaculture produce, and the need for new food supplies This development generates profit and income, but it also bears risks of negative environmental impact, such as pollution or biodiversity change (Tovar and Moreno, 2000) The main input in most intensive fish culture systems is feed of fish in the form of wet homemade feed, trash fish, and pellets These feeds are partly transformed into fish biomass and partly released into the water as suspended solids or dissolved matter such as carbon, nitrogen and phosphorus These wastes are originating from surplus food, faces and excretions via gills and kidneys Other pollutants are residuals of drugs used to cure or prevent diseases

Aquaculture feeds and feeding regimes can play a major role in determining the quality and potential environmental impact or not of finfish and crustacean farm effluents (Tacona and Forster, 2003) This is particularly true for those intensive farming operations employing open aquaculture production systems, the latter including net cages/pens enclosures placed in rivers, estuaries or open-water bodies, raceway or pond production systems This is perhaps not surprising since the bulk of the dissolved and suspended inorganic and organic matter contained within the effluents of intensively managed open aquaculture production systems are derived from feed inputs, either directly in the form of the end-products of feed digestion and metabolism or from uneaten/wasted feed, or indirectly through eutrophication and increased natural productivity

An Giang province of Vietnam is one of the provinces in Mekong Delta where many types of intensive fish culture systems i.e fish pond, floating cages and pens, are located An Giang province located on the border to Cambodia is the centre of production

(70 to 80 %) of Vietnamese’s Pangasius gigas (Basa fish), Pangasius hypophthalmus (Tra

fish) come from this region (FAO, 2005) The number of floating cages in the province

increased from 169 in 2003 to 3,568 in 2004 but 3,531 in 2005 decreased 37 pieces There were 1,167 ha of fish ponds area in 2004 and 1,512 ha of fish ponds area in 2005 Overall production capacities from these systems were 152,507 tons in 2004 and 232,139 in 2005

(An Giang province statistical yearbook, 2005) Mainly Pangasiusis hypophthalmus (Tra

fish) are cultured in floating cages and pens in rivers and canals in An Giang province The

total water area for pens culture and Veo (hapa net) culture for this species were 21 and 80

ha, respectively, in 2003 and the area increased up to 32 and 84 ha, respectively, by 2004 and 313 ha in 2005 (An Giang province statistical yearbook, 2005) The total number of floating cages in total of province increased from 2,126 in 1995 to 3,568 in 2004 These increasing trends might have continued until today

Intensive floating cage and pen culture of Pangasius hypophthalmus (Tra fish) have

been developed and operated by the indigenous knowledge of local farmers (Tan, 2001) which provides a new significant income source, helping to diversify farming activities, reduce risk, alleviate poverty and provide employment opportunities throughout the year This is very important livelihood activity for landless farmers

Floating cage and pen culture in rivers is an intensive operation by nature, have both detrimental and beneficial effect on surrounding environment The major problem areas in river floating fish culture systems are 1) Environment interaction i.e effluent from

this culture disposed of throughout the water body and thus causes a deterioration in the surrounding environmental quality 2) The farmers of An Giang province in and all

Mekong delta are facing lack of Pangasius (Basa fish, Tra fish) fingerling to culture many

years ago due to over exploitation fry natural resource 3) Over use of feed and wet homemade feed such as (Pangasiusis waste, pelleted feed and wet homemade feed) are less stable than manufactured feed, and typically has a higher feed conversion ration than manufactured feed, thus the use of homemade feed can also lead to increased water pollution (Edwards 2004) 4) Outspread diseases and the excessive use of antibiotics in catfish cultivation which is a major problem for the farmers of An Giang province

Therefore, this study was carried out detailed study on fish culture that release effluents and waste to rivers to find ways to reduce negative impacts to the aquatic

environment The study was focuses on Pangasius hypophthalmus (Tra fish) and Tambaqui fish (Colossoma macropomum) floating cages, ponds and pens culture to assess

of technical, environmental and economical factors with a special emphasis on fish feeds use Finally, it is expected to develop recommendations for sustainable development and

management of floating cages and pen culture of Pangasiusis hypophthalmus, Tambaqui fish (Colossoma macropomum) and others fish species in rivers An Giang province,

1.3 Specific objectives

1 To assess and compare the technical, economical, and environmental aspects of selected pond, floating cage and pen culture systems in An Giang province

2 To assess and compare the feed use in these systems e.g Pangasius hypophthalmus,

Colossoma macropomum species

3 To assess and compare the feed waste contribution from there different culture systems

4 To develop recommendations for sustainable management of pond, cage and pen culture in the vicinity of Mekong River, Vietnam

CHAPTER 2 LITERATURE REVIEW 2.1 Basic biology of Pangasius Hypophthalamus

General biology of fish:

Species Pangasius hypophthalmus Sauvage, 1878

Pangasiid species are important for commercial fisheries and aquaculture in Vietnam, Cambodia, Thailand, and Indonesia The taxonomy of this family has been recently reorganized into four genera and 25 species (Vidthayamon and

Roongthongbaisree, 1993) Several of these species (Pangasius bocourti, Pangasius gigas,

Pangasius hypophthalmus, Pangasius larnauddii and Pangasius sanitwongsei) have

economical potential for aquaculture but today the three species of Pangasiid (Pangasius

hypophthalmus, Pangasius larnauddii, Pangasius gigas) are very popular and the most

famous in Mekong River in the Southern Vietnam, Vietnam language called these above

species are Pangasius hypophthalmus (Tra fish) and Pangasius bocourt (Basa fish) but the

English common name is “Striped catfish”

Pangasius hypophthalmus (Tra fish) and Pangasius bocourt (Basa fish) are two of

28 species in the family Pangasiidae, of which the majority, including Pangasius

hypophthalmus (Tra fish) and Pangasius bocourt (Basa fish), are in the genera Pangasius

Pangasiidae species are found primarily in freshwater in countries surrounding the Indian Ocean basin; the largest concentration of Pangasiidae diversity is found in Southeast Asia

(Roberts and Vidthayanon 1991; Gustiano, 2003) Both Pangasius hypophthalmus (Tra

fish) and Pangasius bocourt (Basa fish) are native to Cambodia, the Lao People's

Democratic Republic (Lao PDR), Thailand, and Viet Nam

Knowledge of the biology and ecology of Pangasius hypophthalmus (Tra fish) and

Pangasius bocourt (Basa fish) in the wild is scarce (Hung, 2003) Both species are

omnivorous, and feed primarily on plant matter, fruits, and some mollusks sometimes have

seen small fish (Vidtayanon, 1993); Pangasius bocourti (Basa fish) consumes more fish and crustaceans than Pangasius hypophthalmus (Tra fish) (Poulsen, 2004)

The natural range of Panagius hypophthalmus (Tra fish) is limited to the lower

Mekong Basin, which includes Cambodia, Lao PDR, Thailand, and Vietnam, and the Chao Praya River in Thailand (Roberts and Vidthayanon, 1991; Poulsen, 2004) In the Mekong

River, upstream migration of adult Panagius hypophthalmus (Tra fish) begins in annual

year in November when the water level in the river decreases and continues well into the dry season, at least until February In the late dry season, or the start of the monsoon season, a downstream migration takes place from Khone Falls on the Lao PDR-Cambodia border to the Mekong Delta (Rainboth, 1996; Sokheng, 1999; Kottelat 2001; Poulsen, 2004) During the dry season, deep pool habitats serve as important refuge for adult

Pangasius hypophthalmus (Tra fish), while during the rainy season, the flood plains and

tributaries provide prime feeding habitat (Poulsen, 2004) Sexual maturity of Pangasius

hypophthalmus (Tra fish) in captivity occurs at around more than 3 years of age 4 kg and

total length of 54 cm in nature, (Van Zalinge, 2002) but the good fecundity for this species

at 5-6 years old, although there is no documentation of maturity for Pangasius

hypophthalmus (Tra fish) in the wild (Van Zalinge, 2002) Female of Pangasius hypophthalmus (Tra fish) each produce about 100,000 eggs per kilogram (kg) of body

weight and spawn up to four times per year After spawning, the early larval stage of

Pangasius hypophthalmus (Tra fish) drift downstream with the water current and

eventually enter rearing and feeding habitats on the river’s floodplains (Poulsen et al 2004)

Pangasius hypophthalmus (Tra fish) is one of the largest catfish in the Mekong

River and can grow up to a maximum weight of 70 kg in nature (IG Baird, personal communication) It is very common, commercially important and intensively exploited in the Lower Mekong River and has been widely introduced for aquaculture in Southeast Asia (Roberts and Vidthayanon, 1991; Rainboth, 1996)

(Pangasiid catfishes and cyprinids; Poulsen and Valbo-J_rgensen, 2001; Baird and Flaherty, 2004) make vast migrations between the low to middle basin feeding grounds and upper basin spawning grounds, often located in upland middle-sized river branches

Similarly, the sutchi catfish, Pangasius hypophthalmus (Tra fish) (Sauvage, 1878)

(Pangasiidae, Teleostei), a long-distance migratory catfish occurring in large rivers of the Mekong and Chao Phraya basins, exhibits an annual pattern of migration between feeding and spawning grounds It spawns in the upper stretches of the Cambodian Mekong River between the Khone Falls on the Cambodian/Lao border and the town of Kratie from May

to August (Poulsen and Valbo, 2001) (from The discontinuous spawning habitat consists of rapids and sand banks interspersed with deep rocky channels and pools (Van Zalinge, 2002) It covers about 1% of the feeding area (52,500 km2), which is located in the huge floodplain of Tonle Sap, central and southern Cambodian lower Mekong and the Vietnamese Mekong delta After spawning, adult fish migrate back to the feeding grounds (consisting of inundated forests and other vegetation) and larvae drift to the nursery floodplains located close to the feeding grounds From this point of view, the river basin constitutes one ecological unit interconnecting upstream spawning habitats with downstream rearing habitats

Some differences between of Pangasiusis species studied: Pangasius

hypophthalmus (Tra fish) is the predominant finfish produced in the Mekong Delta region

(Phillips 2002) P gigas (Basa fish) is produced at much lower levels due to the fact that it

is less hearty, grows slower, and is more expensive to produce (Edwards, 2004) The

fecundity of Pangasius gigas (Basa fish) is also up to 10 times lower than that of

Pangasius hypophthalmus (Tra fish), and Pangasius gigas (Tra fish) has a much lower

tolerance for poor water quality than Pangasius hypophthalmus (Tra fish) (Pers Comm.,

as Pangasius hypophthalmus (Tra fish) was thought to be dirty and of poor quality Due to

the ease of production Pangasius hypophthalmus (Tra fish) aquaculture was cleaned up and export of Pangasius hypophthalmus (Tra fish)) has increased under the name of

Pangasius gigas (Basa fish) True Pangasius gigas (Basa fish) is still preferred locally, and

will sell for one third more than Pangasius hypophthalmus (Tra fish) The Pangasius gigas

(Basa fish) that is exported goes to a specialty market (Pers Comm., Philippe Cacot, 2005)

2.2 Wild populations

Over their native range, Pangasius hypophthalmus (Tra fish) stocks are divided into

two distinct populations: stocks in the Mekong River in Cambodia and Viet Nam belong to one population (southern stock); and stocks above Khone Falls in Lao PDR and Thailand form a separate population (northern stock) (Van Zalinge, 2002 and Poulsen, 2004) The southern Vietnam’s stock is subject to more intense fishing than the northern stock, and is larger in size (Poulsen, 2004)

Pangasius hypophthalmus (Tra fish) has been spread more widely outside its native

range than Pangasius gigas (Basa fish) It has introduced to China, the Philippines, Taiwan,

Indonesia, Malaysia, Guam, Bangladesh, and India primarily for the purpose of aquaculture (Van Zalinge et al 2002; Pers Comm., Philippe Cacot, 2005) There is no

evidence of self-sustaining populations of Pangsius hypophthalmus (Tra fish) escaping

from these aquaculture operations or negative ecological impacts from these operations thus far

The commercial fishery for Pangasius hypophthalmus (Tra fish) fry is relatively

new, with collection beginning in the early 1980s There is a general thought that caught fry are better quality than hatchery-reared fry (Trong, 2002) The dais fishery exhibits high seasonality, with peaks in early June, coinciding with the May-August spawning period (Van Zalinge, 2002) In the upstream areas of the Mekong delta, there are plenty of natural resources, good environment conditions and low labour cost and available for Pangasius in the pond, floating cage and pen culture Ministry of fisheries, cited by Khanh 1996 in Vietnam, the early in the monsoon season, wild adult river catfish migrate out of the Great Lake and go down the Tonle Sap River, before swimming up the Mekong River delta to spawn below the Khone Falls on the Lao-Cambodian border, which has suitable environment conditions for gonad development and breeding Traditionally, river culture systems in the South of Viet Nam relied entirely on wild caught fry for cages culture, ponds culture and pens culture Size and colors of fry into three categories, which are 1.3-1.5 cm, 1.5-1.7 cm, and 1.7-2.0 cm, or silver, pink and black, respectively (Department of Freshwater Fisheries 1977; Department of Agriculture of An Giang province 1977; Tien 1995; cited by Khanh 1996), classify Fry In addition to being caught

wild-in the dais fishery, Pangasius hypophthalmus (Tra fish) are taken wild-in other small but

important fisheries by gillnet, hook-and-line gear, seines, trawls, and, to a lesser extent, traps and stunning with explosives Fortunately, extensive education programs have led to

a decline in the use of explosives in recent years

In Vietnam, recent success in Pangasiid breeding (Pangasius hypophthalmus and

Pangasius boucourti) has led to more farmers stocking hatchery-reared catfish, although

some farmers still prefer wild-caught seed Increasingly in the Mekong Delta, Pangasiid

are coming from hatcheries, as demand for post-larvae rise Whether this is because of diminishing wild supply, or high demand, or a combination of both, is not know From

limited information available, there appears to be no evidence that juvenile collection is a wasteful use of the resource, although other species are discarded in the process

2.3 Source of seed stock

Supply of seed stock for Pangasius hypophthalmus aquaculture has traditionally

been dependent on collection of wild fingerling of Pangasius spp fry from rivers (Cacot,

2003; Edwar, 2004) Most of the spawning grounds for both Pangasius hypophthalmus

(Tra fish) and P bocourt (Basa fish) are located within the borders of Cambodia (Poulsen

et al, 2004) Fishers usually target Pangasius hypophthalmus (Tra fish) fry; however, they

are often unable to identify fry at the species level and some fish farmers have reported a mixture of Pangasius species in their ponds In the wild fishery, non-Pangasius species are thrown back or used as fish feed (Bun 1999; Van Zalinge, 2002); an estimated 5 – 10 kg of

fish of species other than Pangsius hypophthalmus (Tra fish) are killed for each kilogram

of river catfish fry caught (Phuong, 1998) The fishery for river catfish fry was outlawed in Cambodia in 1994 and in Viet Nam in 2000, but continues illegally, still supplying fry to aquaculture (Bun 1999; Van Zalinge, 2002) It is unclear the extent to which this practice

is still in use; however, the increase in hatchery production and enforcement indicates that capture of wild river catfish fry is declining; a 1000 - fold decrease in wild-caught fry has been observed in the An Giang province, Viet Nam (Van Zalinge, 2002)

Anecdotally, the number of wild-caught fry has dropped to almost zero, with hatchery fry dominating the supply to aquaculture operations (Pers Comm., Kwei Lin, Asian Institute of Technology, 2005) There are many small scale nursery hatcheries for Pangasius species fry in Viet Nam (< 1 ha in area) that now provide seed stock to Vietnamese river catfish farms These hatcheries produce enough fry for the local market and for export to Cambodia (Edwards, 2004) The first artificial propagation of Pangasius spp catfish occurred in Thailand in 1959 and has since expanded throughout Southeast

Asia (Trong, 2002) In 1999, more than 270 million (Pangasius hypophthalmus and

Pangasius boucourti) fry and fingerlings were produced by a number of state and private

hatcheries (Van Zalinge, 2002)

Table 2.1 Estimated numbers of Pangasius hypophthalmus (Tra fish) fry caught in the dais

fishery in Viet Nam

2.4 Brood stock and rearing conditions

Successfully for breeding Pangasius hypophthalmus and Pangasius boucourti by

Cacot, Muon and Trieu in 1996; Experiments were conducted with brooders raised in floating cages on the Mekong River close to the town of Chau Doc in An Giang province, Vietnam Male brooders were about 8 years of age, with a body weight ranging from 3.3 to 6.9 kg Wood and net cages (50 m3, 6m x 3m x 2.8 m depth) were used for stocking brooders at low density (1.1 fish m3) Brooders were fed with moist pellets (35% moisture) prepared with 33% fish meal, 33% rice bran and 33% C50 Proconco industrial concentrate, including vitamins and mineral premix Water was added (30% total) but cooking was not necessary as the industrial concentrate provided suitable stickiness The pellets contained 42% proteins, 12% lipids and 7% carbohydrates (% dry matter) Food was provided twice

a day at a daily feeding rate of about 1% of the fish biomass (based on the weight of crude ingredients without water added)

2.5 Fish culture systems in An Giang province, Mekong River in Vietnam

Methods of culture vary widely from simple subsistence ponds to large,

industrialized Pangasius hypophthalmus ponds Commercial production of river catfish

occurs either in earthen ponds, floating cages and pens culture in natural water bodies (Hung, 2003) The major culture systems in recent years in An Giang province are intensive pond culture, intensive floating cage and pen culture

2.5.1 Pond culture

Pond aquaculture of river catfish (Pangasius hypophthalmus) has been a tradition

in the Mekong Delta and River Basin for several hundred years Before more technologically advanced methods were introduced in the 20th century, farmers in Vietnam integrated systems of gardens, ponds, and livestock quarters for combined agriculture and

aquaculture, a method known in Viet Nam under the acronym VAC (Edwards, 2004)

Pond culture is the predominant method for producing Pangasius hypophthalmus

(Tra fish) this area in 1999, at nearly ten-fold the production area of the next most common

method Other common aquaculture methods for Pangasius hypophthalmus (Tra fish)

include floating cage culture, ditch culture, and rice-paddy/field culture (Hung, 2003 and Edwards, 2004) Most farms in the Lower Mekong Delta are small-scale, while farms in the Bassac River of Cambodia in the Mekong Delta are large cage-culture operations (Phillips, 2002) In Lao PDR, Thailand, and Viet Nam, river catfish (Pangasiidae) aquaculture operations use more pond culture than cage culture

Farmers collaborating in the last ten years with the Rural Extension for Aquaculture Development (READ) Project in the Mekong Delta area have stocked river catfish (Pangasiid) in poly-culture with 11 other fish species, including common carp, silver carp, Indian carp and silver barb These are stocked in different proportions, depending on the agro-ecological zone, the availability of on-farm feeds and the socio-economic status of the household (READ in 1998, 1999 and 2000) Because they low dissolve oxygen (air breath)

and can tolerate poor water quality, Pangasius hypophthalmus (Tra fish) are often stocked

at densities as high as 20-25 fish/m2, in both monoculture and poly-culture systems

Information of Pangasius hypophthalmus (Tra fish) ponds culture in An Giang recorded:

Pond size from 100 m2 to 7,000 m2; Stocking density and size: 40 fish/m2; 20 g/fish; 40%

water exchange/day; Harvest size 1.1 kg/fish; Survival: 90%; Yield 360 tonnes/7 months; FCR = 1.4 – 1.6; Farm gate price: 14,000 VND/ kg (Amara, 2006)

The production cycle of Pangasius hypophthalmus (Tra fish) comprises one single

cycle in grow-out ponds (Figure 2.1) Fish are usually fed rice bran, broken rice, kitchen

scraps and vegetables In addition, river catfish feed on natural feed, which develops in ponds fertilized by animal wastes, including those of pigs and humans Fish from integrated pond systems often have a muddy off-flavor and the flesh is always darker in color than the flesh of river catfish reared in cages Consumers and the export market in

particular, prefer the white colored flesh of Pangasius hypophthalmus (Tra fish) reared in

cages

Hatcheries Catching wild fry (10-12 days old)

Larvae-rearing in earthen ponds

Advance fingerling growth

in the cages (1-2 months)

Growth-out in ponds

Growth-out in ponds

Source: Hung & Cacot, 2000

Figure 2.1 Aquaculture timeline for both cage and pond production in Vietnam Pond culture tends to use less advanced technology than cage culture, and pond culturists tend to use a higher proportion of wet homemade feeds as well as depend on natural feeds in ponds that are fertilized with animal wastes and poly-culture with other

fish species, such as carps, Nile tilapia (Oreochromis niloticus), and kissing gourami (Helostoma temmincki)… These practices tend to give farmed fish’s meat a muddy flavor

and flesh yellowish color These characteristics are not favored by international markets, thus cage aquaculture is the preferred method of operation for fish being produced for export (Trong, 2002) Despite the higher risks of high stocking densities and poor water flow, which lead to such undesirable characteristics as yellow flesh, pond culture constitutes 50% of total river catfish aquaculture in Southeast Asia (Cacot, 2004)

2.5.2 Cage culture

Cage culture started nearly a century ago in Cambodia (Chevey and Poulain, 1940; Coche, 1978; cited by Hung and Cacot, 2000) It was introduced to Viet Nam when Vietnamese refugees fled Cambodia in the 1960s (MRC 1992) Since then, cage culture has continued to develop and is concentrated along the Vietnamese-Cambodian border in

An Giang and Dong Thap provinces in Viet Nam (Phuong, 1998) (Figure 2.2 and 2.3) shows cage production from 1985 to 1995 for An Giang and Dong Thap provinces in Mekong Delta

Figure 2.2 Annual production of cage culture in An Giang and Dong Thap provinces

Figure 2.3 Proportion of different catfish species in the Mekong Delta in cage production

These are literally floating cages (floating houses) Each floating house has a worker that lives on the structure full-time It costs less than US$ 12,000 to build one of these using local materials This structure is a perfect example of the industrious nature and ingenuity of the Vietnamese people It is not high technology, but is extremely effective at

producing fish Floating cage culture systems are used for both Pangasuis gigas (Basa fish) and Pangasius hypophthalmus (Tra fish); use of one system over the other depends on the

country Fry are wild-caught or hatchery-reared, and kept in ponds until the grow-out stage Stocking density and size: 50-60 fish/m2; 20 g/fish, fish reach marketable size at 1 – 1.5 kg (Hung, 2003) after about 6 to 8 months of culture, starting from fingerlings (approximately

2 months of age) (Edwards, 2004) Feeds and feedings used for floating cage and pen culture in An Giang province which have catfish wash used to Pangasiusis fish specie, wet homemade feed, pellet feed Farm made wet-feed is widely used for example; mix 40% rice bran + 10% soybean meal + 50% fish meal and FCR: 1.8 – 2.0

Floating cage (floating house) culture is the most famous in An Giang province and

it is an intensive culture system since fish are stocked at very high densities (100 kg/cum)

and artificial feed is provided as the only nutrient source for fish growth Pangasius

bocourti (Basa fish) is the main species cultured in cages, contributing 85 percent of the

total floating cages production in the Mekong delta Other Pangasiids contribute 6 percent

of total cages production in Vietnam Floating cage culture development is concentrated in

An Giang and Dong Thap provinces in areas with suitable water currents and locally

available supplies of seed and feed Good infrastructure (roads and waterways), credit

systems and processing factories are also advantageous Pangasius hypophthalmus (Tra

fish) is an omnivore that will feed on rice bran, broken rice and corn, cassava flour, trash

fish, fish-meal and vegetables in culture systems

In Vietnam, rice bran usually contributes two thirds of the diet during grow -out of

Pangasius hypophthalmus (Tra fish) Homemade feeds normally consist mainly of rice

bran, broken rice, trash fish and vegetables In Vietnam, cage feeds are prepared, mixed

and cooked at site, with the feed being presented as wet sticky balls Fingerlings obtained

from the nursing ponds are grown in small cages to advanced fingerlings of 100 g and

these are stocked into grow -out cages Culture is concentrated in Hong Ngu and Tan Hong

districts of Dong Thap province, though there has been a more recent spread to other areas,

including Thanh Binh, Cao Lanh, and Sa Dec town of Dong Thap province but the most

concentrated in An Giang province (Table 2.2)

Table 2.2 Status of Pangasius hypophthalmus pond culture in An Giang province

Fish ponds and pits (ha) 1,118.00 1,079.74 921.45 1,414.53 1,055.70 1,167.02

Fish cages under rafts (pieces) 2,126 3,086 3,237 4,053 3,178 3,504

Statistic yearbook An Giang province (2004)

In modern floating cage culture, cages are placed and maintained in natural water

bodies and consist of wood or steel frames with nylon mesh (near Ho Chi Minh City) or

inox screens, and are attached to drums for floatation (Edwards, 2004; Pers Comm.,

Philippe Cacot, CIRAD, 2005) but river cages culture in An Giang and Dong Thap

province constructed only by good quality wood, inox screens and steel but more

expensive for constructed Cages in the Mekong River Delta range from 50 to 1600 m3 in

size, and larger cages commonly include living quarters for workers on the surface above

the submerged cages (Phillips 2002; Pers Comm., Philippe Cacot, CIRAD, 2005)

At one time, Pangasius gigas (Basa fish) was the predominant species cultured

using cages (Trong, 2002), while Pangasius hypophthalmus (Tra fish) dominated total

aquaculture production (cage and pond aquaculture) Currently, the culture of Pangasius

hypophthalmus using cages has increased to surpass cage culture of Pangasius gigas (Basa

fish) (Pers Comm, Philippe Cacot, 2005)

2.5.3 Pen Culture

Pen culture, like other methods of rearing fish, may be conveniently classified as

extensive, semi-intensive or intensive on basis of feeding and fish density Extensive

culture relies solely on naturally available food such as plankton, detritus, benthos and drift,

and no supplementary feeding is given Semi-intensive culture involves the addition of low protein <10% of feedstuffs, usually compounded from locally available plants or agriculture by products to supplement the intake of natural food, whereas in intensive culture operations, fish rely almost exclusively on an external supply of high protein >20%

of food, usually based on fish meal Recently, it has been reported that Pangasius

hypophthalmus (Tra fish) culture of wild-caught animals within barriers constructed in

(bamboo, wood, and nylon nets) occurs in An Giang province of Viet Nam Pen size from 100m2 to 1,000m2; Stocking density and size: 40 fish/m2; 20g/fish; 40% water exchange/day; Harvest size 1.1 kg/fish;

Discussion of NAGA, World Fish Center Newsletter carried out if technology for culture in pens is improved in terms of pen materials, fabrication, stocking rate, feed and feeding schedule, harvesting methods, etc., it may serve as a cheaper alternative to the expensive land-based nurseries for raising advanced fingerlings for stocking the large rivers and canal in Vietnam

The most of systems intensive Pangasius hypophthalmus pens culture are

distributed in An Giang province and the area of water surface for pens culture and Veo culture (hapas net) for this species in 2003 are 2,180 and rose 3,284 in 2004 (2004 statistical yearbook of An Giang province), maybe the areas of water surface for pens culture and Veo (hapa net) culture will be increased in 2006 and following years and continue develop in the future because this system provide many benefic for many farmers

of An Giang province and Mekong Delta of Vietnam

2.6 Production statistics

Much of the finfish produced in Southeast Asia is consumed locally, although there

is a large export market Pangasius hypophthalmus (Tra fish) is the predominant species reared for export, while Pangasius gigas (Basa fish), considered a superior product, is, for

the most part, consumed domestically (Pers Comm., Philippe Cacot, 2005) In 2003,

production of Pangasius gigas (Basa fish) was estimated to be between 10,000 and 50,000 tons and production of Pangasius hypophthalmus (Tra fish) was estimated to be greater

than 100,000 tons, with production steadily increasing The government of Viet Nam

hopes to increase production of Pangasius gigas (Basa fish) to 50,000– 100,000 tons by

2010 while maintaining the production of Pangasius hypophthalmus at its current rate

(Edwards et al 2004) In Viet Nam, in 2004, production of river catfish for the export

market alone reached 350,000 tons, 90% of which was Pangasius hypophthalmus (Tra

fish) (Pers Comm., Philippe Cacot, 2005) Total production of pangasius for the export

market in July, 2006 (Figure 2.4)

Figure 2.4 Annual production of Pangasius spp for export in the Mekong Delta, Vietnam

2.7 Feeds and Feeding

Feed use in Pangasius hypophthalmus aquaculture is widely varied throughout the four countries that produce the majority of farmed Pangasius hypophthalmus (Tra fish) and

Pangasius gigas (Basa fish) (Vietnam, Thailand, Lao PDR, and Cambodia) Much of the

information available on feed use in aquaculture operations in these countries is specific Additionally, since half of the feed used in river Pangasius spp pond, floating cage and pen culture aquaculture are homemade; there is limited uniformity in feed use in aquaculture operations Feed and feeding used for Pangasius spp floating cage and pen culture in An Giang Province for many years ago such as Pangasius waste feed, Manufactured pelleted feed and wet homemade feed but farm made wet-feed is widely used for example, mix 40% rice bran + 10% soybean meal + 50% fish meal FCR: 1.8 – 2.0 (Amara, 2006) Feeding rate: the firth of Month: 8 – 10% body weight, the second of month: 6 – 7% body weight, the third of month: 4 – 5% body weight, the fourth of month: 3% body weight and from 5 to 7 months: 1.5% body weight (Amara, 2006) but now they reused Pangasius waste after processing for feeding in floating cage and pen culture

Until recently, in Vietnamese river Pangasius hypophthalmus (Tra fish) and

Pangasius gigas (Basa fish) floating cage and pen culture systems, 95 to 97% of floating

cage and pen used homemade feed (Phu & Hein, 2003 Lecturer of Can Tho University)

Current estimates indicate, however, that 50% of Pangasius hypophthalmus (Tra fish) and

Pangasius gigas (Basa fish) cages use wet homemade feed and 50% use manufactured

feed (Pers Comm., Philippe Cacot, 2005) Small-scale farmers use an integrated fisheries/aquaculture system that uses low-value fish species (trash fish), taken from marine or freshwater systems (Edwards, 2004) either through by catch or targeted fisheries, for aquaculture feed Wet homemade feeds vary widely in their ingredients and nutritional value (Edwards, 2004), and can have low and occasionally imbalanced nutritional value, which results in low yield of marketable fishes; high fat accumulation in fish abdomens due to these low nutritional feeds reduces the proportion of fillet meat in the final, processed fish (Phu & Hein, 2003 Lecturer of Can Tho University) Manufactured pellet feed is significantly higher cost than wet homemade feed, as manufactured feeds use imported fishmeal and soybean cake (primarily from the U.S.), instead of the local sources

of “trash fish,” which are thought to be of low quality (Edwards, 2004; Pers Comm., Philippe Cacot, 2005) Materials for making homemade feeds, on the other hand, are locally available and cheap The price of wet homemade feed is about US$0.12 – $0.13 per

kilogram (kg) of feed, and the price for manufactured pelleted feed is around US$0.27 –

$0.30 per kg of feed Hence the feed cost for producing one kilogram of fish can range

from US$0.31 – $0.39 for homemade feed and US$0.38 – $0.45 for manufactured pelleted

feed (Phu & Hein, 2003 Lecturer of Can Tho University) However, these values will vary

greatly depending on the feed conversion ratio (FCR), which will be affected both by

protein content and rearing structure in the aquaculture operation The recent of decline in

the use of wet homemade feeds has, in part, been due to the establishment of a feed

industry, increased large-scale production of Pangasius hypophthalmus (Tra fish), and a

shortage of trash fish, as well as the relationship between trash fish and pathogens such as

Vibrio spp (Pers C and Philippe, 2005)

Due to the low-tech nature of river catfish farms, feeding may not operate at its

most efficient, especially considering the common use of wet homemade aquaculture feeds

Feeds vary in protein content and moisture content, and homemade feeds especially vary in

the type of trash fish and the amount of trash fish used in the feed (Pers Comm., Kwei Lin,

ret Asian Institute of Technology, April 13, 2005) FCRs vary accordingly with each

variation within the different types of feeds Homemade feeds, with unknown moisture

content, typically result in the highest FCRs of any type of feed Subsequently, FCRs are

typically lower for homemade feeds supplemented by manufactured feeds, depending on

cost, and even lower for manufactured pelleted feeds Other studies have calculated an

average FCR for all Pangasius catfish, under all feeding regimes, of 2.5 (Table 2.3,

Edwards et al 2004)

Table 2.3 Aquaculture using trash fish (Edwards, 2004)

Trash fish (t) Species Production (mt) (%) using trash fish FCR Moist/wet feed (t) Min Max

Phu and Hein, indicate FCRs for homemade feeds range from 2.7 to 3.0 and FCRs

for manufactured pelleted feeds range from 1.4 to 1.5 FCRs also vary with stocking

densities and water quality associated with the rearing structure of the aquaculture

operation In experiments done on aquaculture feed, Hung (2001) calculated FCR under a

number of conditions for both basa and Pangasius hypophthalmus (Tra fish) FCRs for

Pangasius hypophthalmus (Tra fish) ranged from 1.34 – 1.82, with higher values for day

feeding than for night feeding, while FCRs for Pangasius gigas (Basa fish) had a much

larger range, from 1.21 – 2.19, with the highest FCR values occurring with 1, 2, or 3

feedings during the day

2.8 Nutritional requirements of Pangasius hypophthalmus

2.8.1 Protein and amino acid of fish

Total protein (amino acid balanced) requirements for optimum growth of catfish

Pangasius hypophthalmus have reported to range from 20% to 30% (Aizam et al., 1983

cited in Alawi, 1989) A minimum level of 25% protein is needed in the diet for optimum

growth of catfish Pangasius hypophthalmus fry in laboratory or intensive culture

(Chuapoehuk and Pothisoog, 1985) The main reasons for such a range are differences in fish size, daily allowance, and amount of non-protein energy in the diet Small catfish increased in weight more rapidly when the dietary protein level was increased from 25% to 35% than did larger fish (Page and Andrews, 1973 cited in Lovell, 1989)

Catfish require essential amino acids (EAA) such as Arginine, Histidine, Isoleucine, Leucine, Lysine, Methionine, Cystine, Phenylalanine, Tyrosine, and Valine Cystine can replace or spare about 60% of methionine on a molar sulfur basis Tryosine can spare about 50% of the total phenylalanine requirement for channel catfish Lysine and methionine plus cystine appear to be first limiting amino acids, followed by lysine (National Research Council, 1983)

2.8.2 Lipid requirement of fish

Lipid requirement of fish varies according to species, sex, and temperature, total energy of feed, lipid type and digestibility In general, optimal dietary lipid level in feed is around 10-20% At these dietary lipid levels, a high efficiency of protein utilization occurs

in fish and has a slight effect on carcass quality, with more than 20% causing increased lipid deposition (Cowey and Sargent, 1979) Generally, if fish are fed with inadequate dietary lipid, storage protein and carbohydrate (glycogen) are used for producing energy supply and growth rate is standard When fish are fed with excess dietary lipid, fat deposition occurs (Henderason and Sargent, 1985)

The use of lipids (fats and oils) in catfish feeds is desirable because lipids are a highly digestible source of concentrated energy, supply essential fatty acids, serve as a vehicle for absorption of fat-soluble vitamins, increase feed palatability, and serve as precursors for steroid hormones and other compounds In the storage form, lipids affect the flavor of fish and help maintain neutral buoyancy The type and amount of lipid used in catfish diets are based on essential fatty acid requirements, economic, and quality of fish desired

Essential fatty acids (EFAs) are fatty acids that cannot be synthesized in the animal’s body; thus; they must be provided preformed in the diet EFA requirements for catfish and most other warm water fish have not been precisely defined, but it appears that catfish require a small amount (about 0.50% - 0.75%) of n 3fatty acids This level can be supplied by fish oil Natural pond food organisms may also be a source of EFA Generally, lipid levels in catfish feeds are kept below 6% (Tucker, 1985)

2.8.3 Carbohydrate requirement of fish

Carbohydrates are compounds of carbon, hydrogen, and oxygen that include sugars, starch, cellulose, gums, and other closely related compounds Carbohydrates serve as the

least expensive source of dietary energy and aid in the pelleting quality of practical catfish feeds Therefore, some form of digestible carbohydrate should be included in fish diets (Garling and Wilson, 1977 cited in Tucker, 1985)

Carbohydrate may also serve as precursor for various metabolic intermediates necessary for growth Thus, in the absence of adequate dietary carbohydrates or lipids, fish will utilize dietary protein to meet their energy needs When adequate energy is available from either carbohydrate or lipids, much less protein will be used for energy and most will

be used for growth (Tucker, 1985)

2.8.4 Minerals requirement of fish

Fish require the same minerals as warm-blooded animals for tissue formation and various metabolic processes In addition, fish utilize inorganic elements to maintain osmotic balance between fluids in their body and the water Minerals in the water can make significant contributions to the fish’s requirements for some minerals Most fish can absorb a major part of their calcium requirement from the water, across the gills, except when the water is unusually low in dissolved calcium (National Research Council, 1983)

A dietary source of phosphorus is essential for fish because levels of dissolved phosphorus are very low in natural waters in relation to calcium Dietary deficiencies in phosphorus have caused reductions in growth rate, appetite, and body content of calcium and phosphorus in channel catfish (Lovell, 1984) Minimum requirement for available phosphorus in diets for rapidly growing channel catfish is approximately 0.45%, whereas dietary calcium is usually not considered in feed formulation (Lovell, 1989)

Natural feedstuffs are usually adequate in potassium, magnesium, sodium and chlorine for normal growth of animals unless there is a high rate of mineral loss These elements are probably available in sufficient quantity in practical fish feeds without mineral supplementation However, fish feeds low in animal products may be deficient in trace minerals, so a trace minerals mixture containing zinc, iron, copper, manganese, iodine and selenium should be added to diets containing largely plant ingredients A premix to provide the requirements of zinc, iron, manganese, iodine, copper, and selenium are recommended in commercial feeds

2.9 Environment impacts

2.9.1 Effluent effects

While both of ponds, floating cages and pens aquaculture systems are used for

Pangasius gigas (Basa fish) and Pangasius hypophthalmus (Tra fish), cage aquaculture is

the more technologically advanced method, thus it is utilized more for the export market The cages utilized are essentially open net pens placed within the Mekong River Delta, so effluent from the aquaculture operations is not treated before flowing out of the cages into the surrounding environment

There is concern regarding pollution from cage and pen effluent, as well as regarding deterioration of water quality and an increase in observed fish disease outbreaks (Phillips, 2002) Combined with high water temperatures, ammonia, nitrates, and organic matter released in fecal wastes lead to rapid growth of algae and aquatic plants, and can result in severe algal blooms and eutrophication of water bodies Low levels of dissolved

oxygen in natural water bodies resulting from the decomposition of plants and other organic matter could have affects on local fisheries, water quality, and other local resources (Pers Comm., Philippe Cacot, 2005) The Vietnamese government also suggests that the carrying capacity of the Mekong River is high if factories are prohibited from discharging effluents into the river (Edwards, 2004), while others observe that the impact of fruit and rice production contributes significantly more to environmental degradation than does aquaculture (Pers Comm, Philippe Cacot, 2005)

The purposes of study are to investigate the cage culture system and its related environmental conditions, (a) to determine the quality and quantity of pollutants produced

by cages and pen, (b) to detect the fate of pollutants in the river, and to recommend methods for pollution mitigation in cage culture because of the environmental impact of fish cage or pen culture is an issue of increasing concern, since last two decade (Beveridge,1984) but for cage and pen culture in Mekong River Delta and An Giang province, Vietnam they have many research on some issue for environment impact following:

Sitting and locations for cage production in Mekong River Delta is relatively benign The environment in this region is already highly degraded from non-aquaculture sources, and the area is heavily used by a large human population Additionally, large-scale floating cage and pen aquaculture serves a dual purpose when combined with housing, which is built above submerged aquaculture cages (Phillips, 2002)

In the Mekong River Delta, typical stocking densities of Pangasius gigas (Basa

fish) and Pangasius hypophthalmus (Tra fish) are 200 – 300 fish/m3 (Phillips, 2002) or 100 kg/m3 (Trong, 2002), which are considered intensive production levels Despite intensive production levels and the high pollution loadings, results from various studies show that some 23% of C, 21% of N and 53% of P of feed input such as Pangasiusis waste, homemade feed and pelleted into the cage culture system is being accumulated in the bottom sediments and the significant impact is normally confined to within 1 km of the farm The major impact is on the bottom, where high sediment oxygen demand, anoxic sediments, production of toxic gases and a decrease in benthic diversity may result Decreases in dissolved oxygen and increases in nutrient levels in the water are also evident but are normally confined to the vicinity of the farm

The presence of intensive floating cage and pen culture in both An Giang province and Mekong Rivers in Vietnam has produced a heavy impact on the environment so based

on measured levels of carbon (C) phosphate (P) and Nitrogen (N) the trash feeds, excess biomass and carrying capacity was compound Excess trash fish and homemade fed to fish

sinks to the bottom of floating cages and pens, decomposes, and resulting organic and nutrient wastes become bound to sediments to be liberated as dissolved nutrients, whereas nutrients from excess dry feed are dispersed mostly in freshwater column, so we should be estimates of carrying capacity in this river Pollution loading being much higher in open cage culture systems where trash fish is used as feed

2.9.3 Water flow and currents

Flow in floating cage and pen operations is highly variable due to strong seasonal affects, so intensive aquaculture, relative to flow, during the dry season may be minor during the rainy season Feeding rates vary with the availability of feed (Heng, 2004); meaning that the quantity of wastes also varies, further contributing to high variability in effluent Other variations in effluent come from variability in feed type and quality Homemade feed and trash fish are less stable than manufactured feed, and typically has a higher feed conversion ratio than manufactured feed, thus the use of homemade feed can also lead to increased water pollution (Edwards, 2004)

The flow water through enclosures is affected by drag forces exerted by framework and netting Floating cage and pen culture can have a considerable impact on local currents, and this has a number of implications Excessive densities of floating cages and pens culture on Mekong River, An Giang province have to concern sensibly Sediment transportation in aquatic system, though influenced by a number of factors, is principally determined by current flow Situation problems caused by enclosures are most likely to occur in rivers and in areas of lakes where large rivers flow in Here the dispersion of sediment carrying plume, which is determined by the horizontal water current speed Of more importance which are effects of reduced current on the fish culture operation The flow of water through the system governs the supply of oxygen and the removal of toxic waste metabolites from the vicinity of the fish and in extensive and semi-extensive culture;

it also controls the supply of plankton

2.10 Basic biology of Colossoma macropomum

Family: Characidae (Characins),

Subfamily: Serrasalminae

Order: Characiformes (characins)

Class: Actinopterygii (ray-finned fishes)

(Cuvier, 1918)

Fishbase: Tambaqui, maximum size is 108 cm total length and maximum published weight is 30.0 kg Environment of species is freshwater species; pH range is 5.0 – 7.8 and depth range 5 m and climate is tropical: 22 – 28°C; 15°S - 35°S Importance: minor commercial fisheries; commercial aquaculture and aquarium is public aquariums and the

resilience: Medium, minimum population doubling time 1.4 - 4.4 years Distribution:

South America: Amazon and Orinoco basins as wild form; pisciculture form largely

distributed in South America Asia: Chinese, Vietnam Biology: This species is usually

solitary Adults’ fish stay in flooded forests during first 5 months of flooding and consume but fruits and grains Young and juveniles live in black waters of flood plains until their sexual maturity Feed of collossoma is on zooplankton, insects, snails and decaying plants Used in aquaculture because it can live in mineral poor waters and is very resistant to diseases

This species has been imported to Viet Nam since 1998 In 2000, seed production

for Colossoma brachypomum applying technology of Chinese was successful Colossoma

brachypomum is in the water environment having the temperature of 21-320C, but the suitable temperature is between 28 to300C (Nguyen Manh Hung, 2003) This species is bad

at standing low temperature; below 10oC fish has abnormal symbols and die Colossoma

brachypomum can live normally when the salinity is below 5 – 10 ‰, and it will die when

the salinity is 15 ‰ It can live in narrow environmental aquatic such as pond, lake and swamp with the pH of 5.6 to 7.4 Its habit is living and moving in fish school (herd instinct) About the form traits, the diameter of its eyes is 1/4.5 the length of its head It has two jaws, upper jaw and lower jaw There are two rows on the upper jaw, the outside row has 10 teeth, the inside row has 4 teeth There are two rows on the lower jaw, the outside row has 14 teeth with 6 big teeth and 8 small teeth, the inside row has 2 teeth and its surface has saw – tooth appearance

Its belly fin and anus fin have red color Its tail-fin has some dark points and this species is able to change its color depending on the living environment Its stomach is comparatively big, having U size The length of the intestine is 2.5 the length of its body

There is a lot of fat around the intestine and viscera Colossoma brachypomum is

omnivorous species It can eat aquatic plants, shrimp, fingerling, mollusks It catches preys

actively, and swallows quickly The sample food in the stomach of Colossoma

brachypomum caught in pond is mainly fibre of plants, cereal, and rice In Amazon River,

Braxin, Freshwater Colossoma brachypomum is mature when it is 32 months and it has the ability of nature breeding However, Colossoma brachypomum cultured in pond can not

breed naturally but need to be injecting Gonadotropine for artificial breeding This is

checked in some countries having developing freshwater Colossoma brachypomum culture

such as China, Taiwan, Thailand, and Viet Nam Due to the habit of being omnivorous, catching preys in fish schools, testing or commercial culture of this species should be limited in safe region (High dyke, pen and cage net) It should be not cultured in region frequently having flood and in region sensitive about ecology

CHAPTER 3 MATERIAL AND METHODS 3.1 Steps of the study

Overall steps in this study are as follows:

Step 1: Socio-technical survey on the fish production process using cages, pens and ponds

on the Mekong River and its vicinity In this stage, details of input and output analysis were conducted and several farms were selected for further study Total number of cages, pens and ponds around the selected area of Mekong river in An Giang province was identified using secondary data and aerial photographs (if available) from the provincial government

Step 2: Assess effluent and feed waste contribution to aquatic environment by selected farms The main concentration was suspended solids, N and P release by these systems It

is also expected to determine the carrying capacity of these systems taking FCR, DO availability, toxic wastes such as ammonia in river water and metabolic waste production into account

Step 3: Laboratory studies: A digestibility trial was conducted using on-farm feeds (or

simulated on-farm feed) to estimate dry matter, N, and P retained by fish (Pangasius

hypophthalmus and Colossoma brachypomum) and fecal and excretory waste contribution

to the environment from the different type of fish feeds

Step 4: Assess and compare the different systems taking production efficiency and negative environmental contribution into account Once this exercise is finished, it is expected to develop recommendation for sustainable management of these culture systems taking findings of the study into account

3.2 Socio-technical survey

3.2.1 Study areas

The sampling area was divided into 3 locations i.e upstream, culture site and down stream of the sampling area Specifically, the sampling protocol aimed at comparing water quality parameters between dry season, wet season and flood season; and comparing of feeds used between culture systems

This study was conducted in My Hoa Hung village, Long Xuyen city, An Giang province, Mekong River, Vietnam These areas are chosen for research because it has the most number of floating cages, ponds and pens culture

Location of laboratory analysis Can Tho University and An Giang University

Figure 3.1 Study Area Map of An Giang Province, Mekong Delta, Vietnam

Study Location

3.2.2 Secondary data collection

The general information listed below was obtained from Provincial Office, Department of Fisheries and Meteorology Station:

• Detail map of An Giang province;

• Climate parameters: Seasonality, temperature, rainfall, sun sight and radiation and humidity of An Giang province;

• Annual report of Department of fisheries of selected area to get their plans and information: number of ponds, cages, pens and other relationship on the Mekong River and its vicinity;

• Hydrology regime;

• Cage, pen and pond distribution in the study site;

Key informant survey

Key informants i.e experts, government officials were interviewed to receive their opinions and recommendations on clean farm production, and environmental monitoring, and how the guidelines on responsible aquaculture could be implemented The flowings were raised:

• What are the plans for environment monitoring in these culture systems?

• How to provide guidelines on proper management of water quality, environmental impacts from feeds used on these culture systems?

• What are the policies of country and provincial for investment and economic development are encouraged to develop fishery farming and cultivation?

• How to address excessive use of antibiotics in catfish Pangasius hypophthalmus

floating cages and pens cultivation?

• How to help the farmers to set up new farm enterprises to ensure the farming of

hygienic and safe fish that have higher quality attributes?

3.2.3 Technical aspects

Production methods were concerned with input-output relationships A structured

questionnaire was used to interview 20 cage, 20 pen and 18 pond farmers of Pangasius

hypophthalmus and 15 cage farmers of Colossoma brachypomum at random in the selected

culture site to collect the following information:

¾ Characteristics of ponds, cages, and pens:

• Total area (m2);

• Dimension of with, length, and depth or height);

• Shape (rectangle, circle…);

• Location of pond, cage, and pens;

• Construction materials for cage and pen and costs;

• Number of ponds, cages and pens in selected area;

¾ Seed (fry): Type, size and sources; total seed stocking (fish per pond, cage, and pen);

price (VND); quantity and quality;

¾ Fish stocking: density and culture period;

¾ Feed and feeding:

• Feed used: feed type, amount of feed distributed on cage, pond, and pen and feed composition;

• Amount of feed per time and day (kg) on cage, pond and pen to determine pollution from feed used on the river and then to determine the carrying capacity of these systems taking FCR, DO availability, toxic wastes such as ammonia in river water and metabolic waste production into account;

• Feed price (VND);

• Feeding time and frequency (per day);

• Feeding rate: From the 1st month to 6 - 7th month of the last month; % of body weight per day, amount of feed (kg/day) of each months;

• Feed composition; (feed ingredients, % composition, amount (kg), price/kg);

• Feed conversion rate (FCR);

• Antibiotic use: (How much they need? What kinds they used? Why they are needed?);

¾ Water exchange (for ponds) and pumping costs;

¾ Water quality (all systems);

3.2.4 Economics

This is to investigate socioeconomic characteristics of farmers, cage, pond and pen culture practices, investment cost and return, problems, and other information using a structured checklist and open-ended type of questionnaires For example:

- Cost: construction, seed, feed, management and hired labor;

- Revenue: Colossoma brachypomum and Pangasius hypophthalmus sales, exported

3.2.6 Opportunities and constraints

• Feed related: price, quality;

• Water quality and quantity related;

• Policy and regulation related;

• Market related: market demand, export, and domestic;

3.3 Laboratory studies

3.3.1 Feed and feeding sampling

Feeds and feeding used for Colossoma brachypomum and Pangasius

Hypophthalmus of floating cages and pens culture in An Giang province, Vietnam were

studied

• Catfish waste used for Colossoma macropomum;

• Wet homemade used for Pangasius Hypophthalmus

• Pellet feed used for Colossoma brachypomum and Pangasius Hypophthalmus

¾ Feed samplings:

• Fresh feed samples were collected from owners of the selected cages and pens for analysis;

• Samples were taken to analysis in laboratory;

• Amount of fresh feed sampling: 200 to 300 gram per each feeds;

• The samplings were following procedure has recommended for sampling from feed/ingredients from bags or bulks by AOAC, 1980:

¾ All fresh samples was dried to constant weight in the air oven at 100 – 1050 for 24h

to determine dry weight of moisture and dry matter samples by Air Oven Method which is calculation flowing:

)(

)}

(){(

0 1

0 2 0

W W W W

Weight of the dish + wet sample = W1

Weight of the dish + dry sample = W2

Dry matter content of sample (%) = 100 - moisture (%)

The size of samples was reducing by grinding, shredding, homogenization, and milling and then the sample would be analysis in the laboratory:

1 Ash content: The ash content was analyzed using muffle furnace at 5500C for 12 hours

0 1

W W

Weight of clean, dry crucible = W0

Weight of clean, dry crucible + dry sample = W1

Weight of clean, dry crucible + ash = W2

2 Crude protein: The crude protein was calculated by measuring the total Kjeldal nitrogen

content using Kjeltec system 1026 & Distillation Unit (Tecator, 2000) and it was multiplied by 6.25 to estimate the crude protein content

Content (%) =

sampleof

mg

10014.007acid

theofNormality Blank)

Protein (%) = N content (%) x Conversion factor

3 Crude lipid: The crude lipid was analyzed using the Soxhlet Method Petroleum ether

was used as the extraction solvents

)

)(

1 2

W W

Weight of the filter paper = W1

Weight of the filter paper + sample = W2

Weight of the cup + boiling chips = W3

Weight of the cup + chips + lipid = W4

4 Crude fibre: Determination by Weende Method by using the Fibertec System which is

Weight of the crucible + Dry residue = W2

Weight of the crucible + Ash = W3

5 Digestibility markers: Determination by Hydrolysis Resistant Organic Matter

(HROM) which is calculation flowing:

Weight of the crucible + dry residue = W2

Weight of the crucible + ash = W3

6 Nitrogen free extract (NFE):

NFE was calculated by subtracting the sum of crude protein (CP), crude lipid (CL), crude fiber (CF), and ash from 100

NFE (%) = 100 – [(CP (%) * 4) + (CL (%) + CF (%) + Ash (%)]

7 Digestible energy (DE): DE was calculated as following:

DE (Kcal/100 g feed) = [(CP (%) * 4) + (CL (%) * 8) + NEF (%) * 2.5]

Where 4, 8, 2.5 are values of digestible energy (Kcal) for 1g of protein, lipid and NFE, respectively, which were recommended for striped catfish, (Jantrarotai, 1992)

8 Growth and response and feed utilization:

Daily weight gain (DWG), Food Conversion Ratio (FCR), Protein Efficiency Ratio (PER) and Apparent Net Protein Utilization (ANPU) were calculated using following formulas:

DWG (g/day) = Average final weight (g) – Average initial weight (g)

Culture period (day)

or FCR = feed consumed/ fish total production

Dry feed intake (g)

FCR =

Wet weight gain (g)

Wet weight gain (g)

PER =

Dry protein of protein intake (g)

(Final body protein – Initial body protein)

ANPU = x 100

Dry protein of protein intake (g)

Table 3.1 Parameters and analysis of feed

Dry weight (moisture) Air Oven Method Osborne and Voogt, 1978.

Ash content Air Oven Method Osborne and Voogt, 1978.

Crude protein Micro-Kjeldahl Method Tecator, 2000

Crude lipid Soxhlet Method Tecator Soxtec System Manual HT 1043-001 Manual 1983

Crude fibre Weende Method by Using the Fibertec System Tecator Fibertec M6 1020/1021 Manual, 2001

Kirk and Sawyer, 1981

Digestibility markers (Dry matter)

Nitrogen (N)

Phosphorous (P) Hydrolysis Resistant Organic Matter (HROM) Buddington, (1980),

Samples were analyzed in triplicate This samples was surveyed to get information

on quantity in of fish feed used, feed conversion ratio is to calculate the feed eeficiency fish biomass, environmental impacts from fish culture

3.3.2 Water quality

3.3.2.1 Hydrological parameters

The floating cage and pen culture area were divided into three equal sessions upstream,

inside, and downstream of floating cages and pens culture

Water currents (water flow rate) were measured at 2 points (water inflow and water outflow) at each point, the water current were measured at surface, middle and bottom of floating cages and pens by using a current meter (Hydro-Bioskiel)

Water depth measured by mark bamboo sticks or interview farmers of the floating cages, pens and ponds

3.3.2.2 Water quality samplings

Table 3.2 Samplings were carried out on the flowing three seasons in area selected

Time Season

1 th for sample collection August, 2006 (beginning and raining of flood season)

2 th for sample collection October 2006 in wet season (the top of flood season)

3 th for sample collection December 2006 in dry season (the end of flood season)

The sampling protocol was designed to consider “worst-case” scenarios of water

quality in Mekong River and comparison of two seasons i.e beginning and raining of flood

season and beginning and raining of flood season);

The samples were carried out at three locations (Figure 3.2)

• Upstream , culture site, and downstream;

• Distance of location 1000 m from culture site between of upstream and

downstream;

Water samples were collected from three cages, pens and ponds;

Composite water samples were taken on each cage, pen and pond:

• One meter of location distance the water inflow and water outflow from each cages

and pens;

• Two sites of cage and pen: water inflow, and water outflow;

• Two sites of pond: Water pump in and water pump out

• The samples were taken at three depths at (0.5 cm of surface, 1.5 m of middle, and

2.5 m of bottom);

• Water quality parameters were determined at 07 a.m to 10 am;

• Water samples were taken 01 liter per sample and analyzed in laboratory:

+ Water temperature (T0C), dissolved oxygen (DO) and pH were measured

immediately at three depths (0.5 m, 1.5 m and 2.5 m depth)

+ Total ammonia-nitrogen NH3–N (TAN: mg/L), total nitrite nitrogen NO-2 -N (mg/L),

total Nitrate nitrogen NO-3 -N (mg/L), total suspended solids (TSS), total ammonia

nitrogen (TAN), total phosphate (TP) were analysized in the laboratory;

The water samples for dissolved nutrient analyses were freezing when transporting

and stored on ice (40C - 150C) and then transported on the same day to the Laboratory with

in 12-15 h after field collection

Table 3.3 Parameters and analysis of water quality

Temperature ( 0 C) DO meter method YSI model 55/12 FT

meter Disolved oxygen (DO) DO meter method YSI model 55/12 FT

(mg/L)

Phenate method or indophenol method (Spectrophotometer) APHA, 1998 Nitrate nitrogen NO -3 -N

(mg/L)

Cadmium reduction method (Spectrophotometer) APHA, 1998 Total phosphorous

(TP : mg/L) Persulfate digesttion method APHA, 1998

Total suspended solids (TSS) Residual on GF/C paper filter and dry

in oven for 24 hrs at 1030C - 1050C APHA, 1998

(1) (2)

Figure 3.3 Top view of sampling site at the pond culture

Figure 3.2 Top view of sampling site at the Pangasius cage and Pen culture

Figure 3.4 General view of the field measurement at My Hoa Hung, Long Xuyen city, An Giang province

Culture sites of 3 cages, ponds and pens random (Middle stream location)

Upstream

Main River (Mekong River)

Pump out Pump in

Floating House

Water inflow

1m from cage

Water outflow 1m from cage

3.4 Assessment and comparison of the different systems

• To assess water quality and level of water pollution from feed used on different of

culture systems such as pond, floating cage, pen between Colossoma brachypomum and Pangasius Hypophthalmus fish species

• To compare efficiency and negative of feed used from wet homemade feed, pellet feed and pangasius waste to contribute in fish farmers

• Identify the efficient way to feed used such as trash fish for homemade feed and pangasius waste feed from processing factories to reduce environment impacts and pollution

• To assess and compare the production economics between these system culture with difference of feed used;

From this result of study was recommend for the Vietnamese farmers have to good idea of the new adverse of positive for the factors impacts to environment; and then Vietnamese government would be needs to issue guidelines to clean farm production and

to establish good plans for sustainable development on these systems in this area in Mekong River, An Giang province,

The important for the Department of Fisheries or extension officers, they need to provide guidelines on proper management of water quality because they are important for a successful culture operation if not the environment reliable would be damage seriously The periods of poor growth, disease and parasite outbreaks, and fish kills could be traced

to water quality problems

3.5 Data analysis

Evaluation of Environmental impacts: MS Excel was used to store all survey data, and to generate tabular and graphical outputs for different types of data A simple cost-benefit analysis was conducted to compare economic returns of different cage culture practices (Shang, 1990) Mean were compared by analysis of variance (ANOVA) followed

by Duncan’s multiple range test (DMRT at α = 0.05) If an initial analysis reveals no significant differences between means from surface, middle and bottom samples, data from surface, middle bottom samples were pooled

3.6 Assessment of effluent and feed waste contribution

3.6.1 Estimates mass balance of waste production

The most estimates of waste production usually from the temperate carnivorous

fish species such Colossoma brachypomum and Pangasius Hypophthalmus so in this

research we were carried out wastes production from theses system of two species in An Giang province some points following:

• To estimate of the amount of waste material generated from feed using food conversion rate (FCR), digestibility and faecal composition;

• Using the above data, produce mass balance equations for Colossoma

brachypomum and Pangasius Hypophthalmus species taking nitrogen (N),

phosphorous (P) into account;

Use general equations used by Iwama, 1991 the estimations to be made:

Given:

• UW = % uncaptured feed waste/100 (i.e., ratio of total food un-captured to total

food fed)

• F = % faecal waste/100 (i.e., ratio of total faecal waste to total food uneaten)

• FCR = food conversion rate (weight of food fed/weight gained)

• FD = production (increase in fish biomass);

• O = total output of particulate organic matter

Then:

• TU = total food un-captured = TF x UW

Uptake in Fish

Dissolved in water

Figure 3.5 Mass balances for phosphorus and nitrogen load from cage and pen fish farming

(Wallin and Hakanson, 1991)

UM = Mass of N, P, output from un-captured food

K = % of each component in food/100

E = % each component in faeces/100

3.6.2 Estimates of nutrient budget in pond, cage and pen culture system

Source: Dr Yang Yi

Natural environment (source water)

Feed (100%)

Pond

Dissolved (10%)

Fish products (75%)

Waste feed (15%)

Assimilation (50%)

Waste products (50%)

Figure 3.6 Nutrient budgets of cage, pen and pond

Figure 3.7 Nutrient budgets of cages in the river From nutrient budget in pond, cage and pen: amount of nitrogen (N) and phosphorous (P) intensive culture could be calculated as in following example:

• Total fish production farmer or total of dry biomass: kg (get from survey);

• Feed consumed (used): kg (survey);

• FCR = feed consumed/ fish total production;

• Waste material from uneaten feed and metabolize (kg dry matter) = feed consumed (kg) - dry biomass (kg);

• (%) nitrogen N and (%) phosphorous P of feed contains (Laboratory)