FARMING FRESHWATER PRAWNS

A manual for the culture of the giant river prawn
(Macrobrachium rosenbergii)

FAO
FISHERIES
TECHNICAL
PAPER
428

The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

ISBN 92-5-104811-8

All rights reserved. Reproduction and dissemination of material in this information product for educational or other non-commercial purposes are authorized without any prior written permission from the copyright holders provided the source is fully acknowledged. Reproduction of material in this information product for resale or other commercial purposes is prohibited without written permission of the copyright holders. Applications for such permission should be addressed to the Chief, Publishing and Multimedia Service, Information Division, FAO, Viale delle Terme di Caracalla, 00100 Rome, Italy or by e-mail to copyright@fao.org

FAO 2002


Table of Contents

ABSTRACT

PREFACE

INTRODUCTION

CHAPTER 1.BIOLOGY

1.1 Names, natural range, and characteristics of freshwater prawns

Naming freshwater prawns (nomenclature)

The natural home of freshwater prawns (distribution)

Identifying Macrobrachium rosenbergii from other freshwater prawn species

1.2 The shape (external morphology) and other characteristics of freshwater prawns

1.3 Life history

1.4 Sources of further biological information

CHAPTER 2. SITE SELECTION

2.1 Hatcheries and indoor nurseries

Needs for good quality water

Deciding how much water is needed

Other requirements for hatchery sites

2.2 Outdoor nurseries and grow-out facilities

Choosing your site: topography and access

Choosing your site: climate

Choosing your site: soil characteristics

Choosing your site: power supplies

Choosing your site: fry and consumables

Choosing your site: labour

Choosing your site: sympathetic authorities and technical assistance

CHAPTER 3. BROODSTOCK

3.1 Obtaining and selecting egg-carrying females

Obtaining berried females

Genetic improvement

3.2 Holding your broodstock in temperate zones

3.3 Managing your broodstock

CHAPTER 4. HATCHERY PHASE

4.1 Buildings and equipment facilities

Basic site and building requirements

Equipment and the distribution of water and air

4.2 Hatchery management

Water treatment

Starting your larval batch

Routine work

Feeding

Hygiene, health and management problems

Monitoring performance

The greenwater system of freshwater prawn culture

4.3 Harvesting postlarvae

CHAPTER 5. POSTLARVAL HOLDING AND NURSERY PHASES

5.1 Basic requirements and facilities

Holding tanks

Indoor (primary) nursery facilities

Outdoor (secondary) nursery facilities

Nursery cages

5.2 Holding postlarvae before sale

5.3 Transporting postlarvae

5.4 Managing nurseries

Indoor (primary) nurseries

Outdoor (secondary) nurseries

Other systems

CHAPTER 6. GROW-OUT PHASE

6.1 Site requirements and construction

Defining the pond

Supplying water to the ponds

Discharging water from the ponds

Aeration

Miscellaneous

6.2 Management of the grow-out phase

Size variation

Semi-intensive monoculture in tropical zones

Monoculture in temperate zones

Polyculture and integrated culture

6.3 Feeding and fertilization

Feed type

Measuring feed efficiency

Feeding rate

6.4 Health, predation and disease

Watching for signs of problems

Dealing with problems of predation

Coping with diseases and other problems

6.5 Monitoring performance and record keeping

CHAPTER 7. HARVESTING AND POST-HARVEST HANDLING

7.1 Harvesting your market-sized prawns

Cull harvesting

Drain harvesting

7.2 Handling your prawns after harvest and ensuring good product quality

Handling prawns to be sold fresh

Handling prawns to be sold frozen

Handling for live sales

7.3 Code of practice for harvesting, processing and handling prawns

CHAPTER 8. MARKETING

8.1 Marketing your freshwater prawns alive

8.2 Marketing your freshwater prawns fresh or frozen

8.3 Marketing your freshwater prawns at your farm gate

8.4 International opportunities and general marketing strategy

ANNEXES

ANNEX 1. Key to larval stages of freshwater prawns (Macrobrachium rosenbergii)

ANNEX 2. Natural beach filter for seawater

ANNEX 5. Production of farm-made larval feeds

ANNEX 6. Stock estimation

ANNEX 7. Seine nets

ANNEX 8. Size management

ANNEX 9. Farm-made pond feeds

ANNEX 10. Basic code for introductions

ANNEX 11. Glossary of terms, abbreviations and conversions

FINANCIAL CONSIDERATIONS

ACKNOWLEDGEMENTS

REFERENCES


TABLE 1
Body segments (somites) in Macrobrachium rosenbergii and appendage function

TABLE 2
CHARACTERISTICS OF WATER SUITABLE FOR FRESHWATER PRAWN HATCHERIES

TABLE 3
Artificial brackishwater (12 ppt) for M. rosenbergii hatcheries

TABLE 4
Diluting seawater and brine to make brackishwater for larval freshwater prawn culture

TABLE 5
Water quality requirements for freshwater prawn nursery and grow-out facilities

TABLE 6
Example of water requirements for ponds based on various assumptions

TABLE 7
Relationship between temperature, salinity and dissolved oxygen saturation levels (in ppm)

TABLE 8
Hatchery feeding schedule

TABLE 9
Alternative hatchery feeding schedule

TABLE 10
The major diseases known to affect freshwater prawns, and their exterior symptoms

TABLE 11
Prevention and treatment* of freshwater prawn diseases

TABLE 12
Water discharge capacity (in m3/hr) of concrete pipes under various pressure heads

TABLE 13
Sizes of outlet pipes for ponds with monks

TABLE 14
Time taken to drain ponds (in hours) with different drain pipe sizes

TABLE 15
Oxygen transfer efficiencies of basic types of aerator

TABLE 16
Lime requirements for treating the bottom of ponds between cycles

TABLE 17
Average stocking densities and yield of carps, tilapias and freshwater prawns reared in polyculture, based on a literature study

TABLE 18
Examples of major ingredients either used individually or in mixed freshwater prawn grow-out feeds

TABLE 19
Tentative specifications for semi-intensive freshwater prawn grow-out feeds

TABLE 20
General recommendations to restaurants and consumers for handling and storing freshwater prawns


BOX 1
Removal of iron and manganese

BOX 2
Flow-through requirements for ten 5 m3 larval rearing tanks

BOX 3
Grow-out water requirements

BOX 4
Numbers of berried females required

BOX 5
Activating biofilters

BOX 6
Treatment of brackishwater

BOX 7
Regular monitoring of larval water quality

BOX 8
Alternative larval stocking strategties

BOX 9
Recommendations for good larval water quality

BOX 10
Maintenance schedule for recirculation systemsin the morning:

BOX 11
Feeding bsn depends on tank volume, not the number of larvae in it

BOX 12
Additional recommendations for recirculation system hygiene

BOX 13
Notes on potential disease problems

BOX 14
Definitions of farming intensity used in this manual

BOX 15
Systems of management in grow-out ponds for freshwater prawns

BOX 16
Application of rotenone and teaseed cake

BOX 17
Measuring soil pH

BOX 18
Reasons for not applying organic fertilizers

BOX 19
Keeping rooted plants out of your ponds

BOX 20
Size grading

BOX 21
Polyculture of freshwater prawns with carps in China

BOX 22
Examples of integrated freshwater prawn culture in Viet Nam

BOX 23
Example of feeding rate for freshwater prawns

BOX 24
Examples of freshwater prawn (M. rosenbergii) growth and production rates


FIGURE 1
The external features of Macrobrachium rosembergii.

FIGURE 2
These very large Macrobrachium rosenbergii males were obtained
from a fisheries enhancement
programme (India)

FIGURE 3
How to sex juvenile Macrobrachium rosembergii.

FIGURE 4
Notice that the abdominal pleura of the two females with
this BC male Macrobrachium rosenbergii are enlarged to accommodate eggs (Brazil)

FIGURE 5
The major male morphotypes of Macrobrachium rosenbergii are called blue claw (BC), orange claw (OC), and small male (SM) (Israel)

FIGURE 6
The body shape of freshwater prawns (Macrobrachium rosenbergii) is different to that of penaeid shrimp, as these cross sections of the 5th abdominal segments show

FIGURE 7
Freshwater (caridean) prawns can also be distinguished from penaeid shrimp by looking at the second pleura on the abdomen (see arrow)

FIGURE 8a
Grow-out pond inlets need to be screened to exclude predators

FIGURE 8b
Screened inlets being used in this freshwater prawn grow-out pond (Peru)

FIGURE 8c
This type of inlet screen is used in Thailand, especially when ponds are filled by long-tail pump

FIGURE 9

Pumps can be powered by old diesel bus engines (Thailand)

FIGURE 10

More expensive pumps are used in some countries; this one is being used to harvest freshwater prawns (Hawaii)

FIGURE 11
The eggs of Macrobrachium rosenbergii are carried by the (berried) females until they are ready to hatch; as they ripen, they change from orange to grey/black (Hawaii)

FIGURE 12
This hatching system consists of a 300 litre rectangular hatching tank and two 120 litre circular tanks, one for collecting larvae and one to house a biofilter

FIGURE 13a
Airlift pumps can be constructed in many different ways

FIGURE 13b
Airlift pumps keep the water moving and oxygenated (Peru)

FIGURE 14a
Small hatcheries can be very simply constructed (Peru)

FIGURE 14b
Interior of a simply-constructed inland hatchery for freshwater prawns (Thailand)

FIGURE 14c
Buildings are often rebuilt as the hatchery prospers but the structure remains simple

FIGURE 15
Partially covered larval tanks, made from concrete blocks (Thailand)

FIGURE 16
Hatchery layout is site specific; this is one example

FIGURE 17
This shows the water flow through a freshwater prawn hatchery recirculation system

FIGURE 18
There can be a lot of wasted space around circular tanks but none is wasted between these rectangular larval tanks

FIGURE 19
Inside of cylindrico-conical larval tank, showing the central standpipe used during water exchange (Brazil)

FIGURE 20
Some space can be saved by grouping tanks together but there is still some dead space between these cylindrico-conical hatchery tanks (Brazil)

FIGURE 21
The water in these larval tanks recirculates through a shared filter (Brazil)

FIGURE 22
These larval rearing tanks have individual recirculation systems (Brazil)

FIGURE 23
Whatever kind of hatchery tank drain you use, it needs to be protected by a filter sock to prevent the loss of larvae during water-changing operations

FIGURE 24
Turn-down drains are the best way of changing water or harvesting hatchery tanks

FIGURE 25
Tanks for storing hypersaline water and freshwater, and for mixing purposes at an inland hatchery in Thailand; note the roof and side covers for excluding aerial pollution and controlling temperature

FIGURE 26
Installing a ring main air supply system using larger bore piping than you use to connect the main to each valve helps you to ensure that each tank receives the amount of air you wish it to have

FIGURE 27
Close-up of taps for brackishwater, freshwater and air supplies to larval tanks (Brazil)

FIGURE 28
Power supplies are not always reliable. Loss of aeration can quickly cause devastation in a hatchery. This hatchery has not only installed two electrically-driven blowers (one as a back-up) but has also provided a petrol engine so that the drive belts can be rapidly changed if the power fails (Thailand)

FIGURE 29
The water distribution and treatment system is site specific; this is one example

FIGURE 30
The water in physical hatchery filters may flow upwards or downwards; this illustrates an upward-flowing filter

FIGURE 31
Close-up of a biological filter shared between two larval tanks in Brazil, showing the water entering the mechanical filters (foreground), from where it passes through the biological filter and exits back to the two tanks by means of simple airlift pumps

FIGURE 32
There are many types of biological filters for hatchery recirculation systems; these are the most common types

FIGURE 33
Freshwater prawn larvae in tanks are difficult to see; using a white board will help

FIGURE 34a
Tanks need regular siphoning to remove faeces, the larval exoskeletons that are cast off during moulting, and waste food

FIGURE 34b
Good tank hygiene is essential for hatchery success (Hawaii)

FIGURE 35
Many of the larvae that go missing during the larval rearing cycles are not mortalities but are lost through operator error. For example, it is easy to lose larvae during water changing and tank cleaning. Losses can be minimized by filtering the water removed from tanks and returning the live larvae, if healthy

FIGURE 36a
A method of evaluating the quality of Macrobrachium rosenbergii larvae is illustrated in this diagram

FIGURE 36b
This form provides a convenient way of recording your observations on the quality of Macrobrachium rosenbergii larvae

FIGURE 37
Postlarval freshwater prawns can use a nylon screen as an additional surface area in holding tanks (Brazil)

FIGURE 38
Overhead air and water distribution systems are used to supply these indoor nursery tanks (USA)

FIGURE 39
Substrates can be used in nursery tanks to increase the surface area available to juvenile prawns; this substrate consists of the material used to make barriers around roadworks (USA)

FIGURE 40
The standpipe drain in this pond, normally vertical, is turned down to allow water to flow out (USA)

FIGURE 41
Postlarvae in plastic bags can be transported long distances in modified trucks provided with shelves, a small fan, and simple cooling

FIGURE 42
The substrate material shown dry in FIGURE 39 can be seen beneath the water surface in this nursery tank (USA)

FIGURE 43
Macrobrachium rosenbergii
farms can be large (this one was 70 ha) but need careful production, marketing and business management for sustained success (Brazil)

FIGURE 44
The bottoms of grow-out and nursery ponds need to be sloped towards the drainage point and to be smooth; this increases the efficiency of both drain-harvesting and seine-harvesting

FIGURE 45
When you construct ponds in areas where the soil structure is less suitable, the banks will leak less if you bring clay from another site and use it to make an inner impervious core

FIGURE 46
Pond banks should have the proper angle of slope if you want to minimize erosion and cut down the costs of maintenance

FIGURE 47
The bank of this freshwater prawn pond is being eroded because its slope is too steep (Hawaii) The banks of these ponds have had grass turfs laid on them (Brazil)

FIGURE 48
The banks of these ponds have had grass turfs laid on them (Brazil)

FIGURE 49
Pond bank planted with coconut, grass, and banana; besides stabilising the bank this is a form of integrated farming (Thailand)

FIGURE 50
The dissolved oxygen levels of incoming pond water can be increased by rippling and cascading

FIGURE 51
Simple gravel filters on the water intake system help to minimize the predators in freshwater prawn ponds (Peru)

FIGURE 52
Design your water distribution system so that each pond has a separate supply and the discharge from each pond does not enter any other

FIGURE 53
Where the topography of the site makes it feasible, supplying water by gravity keeps the dissolved oxygen level high (Brazil)

FIGURE 54
Supplying water above the pond water level provides some oxygenation, while grass minimizes erosion of the bank (Brazil)

FIGURE 55
There are many different ways of controlling the water entering your ponds: these are some examples

FIGURE 56
The outlet structure, sometimes known as a monk, can be used to control the level of the water as well as to screen the water to prevent the loss of freshwater prawns (Brazil)

FIGURE 57
Most prawns will have been previously removed by seining; the rest are harvested not only at the drain but also by cast net (as shown in this photo from India) while draining proceeds.

FIGURE 58
This freshwater prawn pond has just been totally drained (Thailand)

FIGURE 59
Pond outlets need to be screened to prevent the loss of your prawns; this type of structure can be designed to hold screens and to control the flow rate

FIGURE 60
Long-tail pumps are easily available in Thailand

FIGURE 61
Long-tail pump being used to lift water from a Thai irrigation canal into a supply channel for freshwater prawn ponds (this type of pump can also be used to drain ponds by pumping)

FIGURE 62
Using paddlewheel aerators keeps the dissolved oxygen level high enough to increase stocking levels

FIGURE 63
Power supplies are not always reliable. Loss of aeration at a critical time of the day and/or when ponds are heavily stocked. This Thai farm is using a mobile engine to drive long-shaft aerators in two adjacent ponds

FIGURE 64
Long-shaft aerator in action (Thailand)

FIGURE 65
The sediment in continuously operated freshwater prawn ponds can become so deep that it reduces the water volume and depth and disturbs the drainage pattern; this pond had not been drained for many years (Hawaii)

FIGURE 66
The bottoms of ponds can be tilled with a disc harrow (USA)

FIGURE 67
There are some advantages in rearing freshwater prawns (Macrobrachium rosenbergii) to a larger (juvenile) size before stocking

FIGURE 68
Sudden changes in temperature and pH can cause mortalities when prawns are stocked. Before their release, the bags containing the postlarvae should be floated in your pond to bring the temperature within them gradually to that of the pond. Any adjustments to the pH of the transport water should have been made in the hatchery, before transport (Brazil)

FIGURE 69
When the temperature in the bag is the same as in your pond, the postlarval Macrobrachium rosenbergii can be released (Brazil)

FIGURE 70
Grass is invading the shallow areas of this pond (Brazil)

FIGURE 71
Close-up of material used as pond substrate for Macrobrachium rosenbergii culture (USA)

FIGURE 72
Substrates have been placed vertically in this temperate zone rearing pond for Macrobrachium rosenbergii culture (USA)

FIGURE 73
In this temperate zone rearing pond the substrates have been placed horizontally (USA)

FIGURE 74
Macrobrachium rosenbergii
farming can be integrated with crop and other livestock production; in this case prawn culture is associated with rice culture and vegetable production (Viet Nam)

FIGURE 75
If hatchery-reared Macrobrachium rosenbergii are not available, brushwood can be used to capture wild postlarvae (Viet Nam)

FIGURE 77
Using a lift net for observing feed consumption (Puerto Rico)

FIGURE 76
Feed can be distributed within the pond by simple boats, which can be lifted from one pond to another; manual feeding along at least one side of the pond would be quite difficult in this case because of the method of construction, which has set a water channel in a very narrow pond bank (Thailand)

FIGURE 78
Measuring transparency can be very simple, even when the design of the Secchi disk is unconventional

FIGURE 79
A simple gravel filter on a farm supply system helps to exclude predators

FIGURE 80
Netting can be used to protect freshwater prawns from predators that arrive overland

FIGURE 81
A large BC Macrobrachium rosenbergii broodstock male from the CAUNESP (Aquaculture Center, So Paulo State University, Brazil) being measured in the scientific way (from behind the eye orbit to the tip of the telson)

FIGURE 82
There is a relationship between the total length and the weight of your prawns; this shows a typical length/weight relationship for Macrobrachium rosenbergii

FIGURE 83
You can cull-harvest your ponds by seining the pond towards one end

FIGURE 84
In a longer pond you may find it easier to carry out seining operations with two nets

FIGURE 85
Larger ponds may also be cull-harvested by making several seining operations; beating the water surface with a stick can help to keep the prawns from escaping from the open end of a seine before it is brought to the side of the bank

FIGURE 86
Sorting prawns while seine harvesting

FIGURE 86
Sorting prawns while seine harvesting

FIGURE 87
Market sized freshwater prawns can be kept alive while harvesting continues (Martinique)

FIGURE 88
Prawns destined to be sold alive need clean and well-oxygenated water to keep them in peak condition (Martinique)

FIGURE 89
Cull-harvesting or sampling is an opportunity to check the health of your prawns

FIGURE 90
An internal harvesting sump can be used for Macrobrachium rosenbergii during drain-harvesting

FIGURE 91
Harvesting Macrobrachium rosenbergii from ponds with an internal harvesting sump (Brazil)

FIGURE 92
Cull-harvesting freshwater prawns several times before drain harvesting increases the yield of market-sized animals in your crop (Martinique)

FIGURE 93
The last few prawns may have to be caught by hand, especially when the pond does not drain well (India)

FIGURE 94
Bird predation causes problems during drain harvesting (Hawaii)

FIGURE 95
If you are not marketing your freshwater prawns alive, you should kill-chill them in a bath of iced water immediately after harvesting to get the best quality (Puerto Rico)

FIGURE 96
Freshwater prawns need sorting while being processed (Brazil)

FIGURE 97
Package your prawns attractively (Mauritius)

FIGURE 98
Freshly harvested (blue) Macrobrachium rosenbergii can be cooked (pink) at the pond-side to provide a tasty barbeque (Brazil)

FIGURE 99
Advertise your freshwater prawns at the farm gate (Martinique)

FIGURE 100
Supermarkets sell Macrobrachium rosenbergii in Europe (France)