Freshwater Prawn Farming: Global Status, Recent Research and a Glance at the Future

Home , Fishery, Freshwater prawn farming, Marine shrimp farming, Shrimp farming, Trolling (fishing)

Aquaculture Research, 2005, 36, 210^230 doi:10.1111/j.1365-2109.2005.01237.x

Freshwater prawn farming: global status, recent research and a glance at the future

Michael Bernard New Aquaculture without Frontiers, Marlow, UK

Correspondence: M B New, OBE, Aquaculture without Frontiers, Wroxton Lodge, 25 Institute Road, Marlow, Bucks SL7 1BJ, UK. E-mail: [email protected]

Abstract My paper reviews the current global status of freshwater prawn farming, summarizes some of the A review of the current status of freshwater prawn news and research papers on this topic that have farming globally,with comments on the statistical in- been published since my book was issued (New & formation available is provided in this symposium Valenti 2000), and makes a tentative glance into the keynote paper. A brief overview of the research on future. freshwater prawn farming that has been published in international journals since 2000 is also provided. Finally,some research needs are listed and some sce- Current global status narios for future expansion are explored. First of all this morning, I would like to talk about the global production data. There has been a very rapid Keywords: freshwater prawns, Macrobrachium, global expansion of freshwater prawn farming since global, status, future 1995 (Fig. 1). This is mainly because of the huge production of China but also, in the last few years, because of a rapid take-o¡ of farming in India and Introduction Bangladesh. I am honoured to have been invited to make the key- The top15 producers in 2001are shown in Table1. note address at this most important symposium. My China was by far the leader with over128300 mt.Viet interest in freshwater prawns has been a kind of ob- Nam was second in this league table (28000 mt) but session. I have been working with freshwater prawns the actual production level is a little uncertain be- since 1969 here in Asia, and in North and South cause it is included in the general FAO category fresh- America, the Caribbean and Europe. I have written water crustaceans not elsewhere included (nei). many reviews and articles about this topic. Perhaps However, I believe that most of this consists of Macro- my best-known publication has been the FAO manual brachium rosenbergii production so I have included on freshwater prawn farming that my Thai co-man- it in Fig. 1 and Table 1. India came third, with over ager, Somsak Singholka and I wrote in the 1980s 24 200 mt in 2001, according to FAO. Last month it (New & Singholka 1985). This was translated into was reported (Anonymous 2003c) that 35000 mt French, Spanish, Farsi, Vietnamese and Hindi. How- were exported from India in 2002. ever, over the past 20 years it naturally became The next three places are taken by Thailand, Ban- somewhat out of date. In 2000,Wagner Valenti and I gladesh (which is a major exporter of wild-caught edited what is probably the most up-to-date reference freshwater prawns) and Taiwan. Thailand and text on the topic (New & Valenti 2000). More recently, Taiwan were both pioneers in freshwater prawn FAO asked me to write a new manual on freshwater farming. The FAO ¢gure for Brazil is a times 10 error prawn culture (New 2002a). I hope that this too will in the statistics. Recently I was in Brazil and I con- eventually be issued by FAO in other languages and ¢rmed that current production is in the order of translated by others into additional languages, in- 500 mt year À1, not 5000 mt year À1. The ¢gure cluding Indian languages. Dr C. Mohanakumaran for Ecuador is also suspect; it has remained exactly Nair has kindly agreed to help in this latter task. the same for the last 7 years. Malaysia, where the life

210 r 2005 Blackwell Publishing Ltd Aquaculture Research, 2005, 36, 210^230 Overview of freshwater prawn culture in USA MBNew

250,000

200,000

150,000

100,000

Figure 1 Expansion of freshwater prawn (the FAO data include the 50,000 categories giant river prawn, freshwater shrimps/prawns nei and freshwater crustaceans nei) farming 0 1992^2001 (mt) (FAO 2003). 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001

Table 1 Top 15 countries farming freshwater Macrobra- Thailand, Taiwan and Bangladesh are the main chium rosenbergiiÃ in 2001 (FAO 2003) producers. Production in Thailand is starting to rise again. Production in Malaysia, although relatively Farmed small compared with other Asian countries ex- production panded rapidly between 1997 and 2000 but fell back # Country in 2001 (mt) Notes somewhat in 2001. Expansion has been much more 1 China 128 338 rapid in India and Viet Nam than elsewhere. In the 2 Viet Nam 28 000 Freshwater crustaceans nei Indian State of Andhra Pradesh alone, production is (thought to be mainly now 27000 mt (Anonymous 2003a), up from 400 mt M. rosenbergii) 3 India 24 230 only 5 years ago. Further substantial expansion is ex- 4 Thailand 12 067 pected, asIam sureweshall hear inthis symposium. 5 Bangladesh 7000 Most freshwater prawns are produced in Asia but, 6 Taiwan 6859 as shown in Fig.3, Chinese production is much more 7 Brazil 5380 10 error in FAO’s 2001 Â than all the otherAsian countries put together.Three statistics (Brazil was really #9, after Malaysia) species are currently grown in inland waters in 8 Ecuador 800 Possibly incorrect? China; two are Macrobrachium spp. but the other is 9 Malaysia 752 themarineshrimpPenaeus vannamei. Macrobrachium 10 Dominican Rep 62 nipponense is common in Chinese inland capture 11 Guatemala 53 Includes 3 mt of other ¢sheries. Its maximum size is 86 mm for males freshwater prawn species 12 Senegal 50 and 75 mm for females. It can naturally reproduce 13 Mexico 48 in freshwater and it is one of the few Macrobrachium 14 USA 44 species that has a temperate distribution. These 15 French Guiana 25 facts, and its popularity with Chinese consumers Others 153 make it attractive to farm. However, M. rosenbergii ÃThe FAO data includes the categories giant river prawn, fresh- is regardedas the major species for the export market water shrimps/prawns nei and freshwater crustaceans nei. for freshwater prawns that China hopes to develop. nei, not elsewhere included. Although some work on its culture was reported in the1970s, real commercial production of M. nipponense did not begin until the 1990s at about the cycle of M. rosenbergii was ¢rst closed, is now a major same time as the culture of M. rosenbergii began producer. The other countries are quite modest pro- to take o¡ in China (W. Miao, pers. comm. 2003). ducers so far. By now, the quantity of M. nipponense produced in Figure 2 shows the production of M. rosenbergii farms is about the same as that obtained from in Asia; output in China dwarfs the scale of other the capture ¢shery. Estimated production of the indi- producing countries. After China, India, Viet Nam, genous M. nipponense is rapidly catching up with the

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140000

120000

100000

80000

60000

40000

20000 Figure 2 Farmed production of Macrobrachium rosenbergii (the FAO 0 data include the categories giant river prawn, freshwater shrimps/prawns INDIA CHINA nei and freshwater crustaceans nei) TAIWAN VIETNAM MALAYSIA THAILAND in major producing countries in Asia BANGLADESH in 2001 (mt) (FAO 2003).

CHINA OTHER ASIAN TOTAL REGION 250000

200000

150000

100000 Figure 3 Trends in farmed Macro- brachium rosenbergii (the FAO data 50000 include the categories giant river prawn, freshwater shrimps/prawns 0 nei and freshwater crustaceans nei) 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 production in Asia (mt) (FAO 2003).

production of the introduced M. rosenbergii (Fig. 4). tion in Brazil, after declining between 1993 and So far, China has not reported its production of 1999, now seems to be increasing again. The Brazi- M. nipponense in its o⁄cial statistical returns to lian government has been concentrating on the pro- FAO. An estimated production of 15000 mt of motion of marine shrimp farming but it is hoped that this species was reared in China in 1999 (Wang & it may now become also interested in a form of aqua- Qianhong 1999) and 120 000 mt in 2001 (W. Miao, culture that may be more sustainable, namely the pers. comm. 2003). In addition to these two species, culture of freshwater prawns. One of the universities experimental culture of one of your own indigenous there has a large team working not only on the cul- prawns in India, M. malcolmsonii, has started ture of M. rosenbergii but also on an indigenous spe- in China. cies, M. amazonicum, which is thought to have great Recorded production in Central and North Ameri- potential for small-scale farms in the Amazonia re- can countries is quite small (Fig.5). Only four nations gion, where it is a feature of the capture ¢shery.The produced more than 40 mt in 2001 ^ the Dominican maximum size of M. amazonicum males has been var- Republic, Guatemala, Mexico and the USA. Figure 6 iously reported as 110^150 mm, while the maximum shows the data for South America. The ¢gures for female size recorded is110mm. Brazil have been adjusted but I have not changed the There is very little production outside Asia and FAO ¢gures for Ecuador, although I remain sceptical South and Central America (Fig. 7). Senegal and about them. The encouraging thing is that produc- Mauritius, both in Africa, are the leaders but their

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140,000 120,000 100,000 80,000 60,000 40,000 20,000 0 Figure 4 Chinese farmed production of 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 Macrobrachium nipponense is catching up with M. rosenbergi (the FAO data include M. nipponense (estimate from Miao Weimin 2003) the categories giant river prawn, fresh- M. rosenbergii (FAO 2003) water shrimps/prawns nei and freshwater M. nipponense (estimate from Wang & Qianhong 1999) crustaceans nei) (mt).

Figure 5 Production of farmed 10 Macrobrachium rosenbergii (the FAO data include the categories giant river 0 R E S A IA E A prawn, freshwater shrimps/prawns O ICA RA IQUE AM US AD OUP MA N LUC NAM V DU MEXICO . nei and freshwater crustaceans nei) L EL N JA PA T DOMNICA GRENADAD O RTIN S URI SA A H S in Central and North America in COSTA RICA U GUATEMALA MA EL G PUERTO RICO 2001 (mt) (FAO 2003). DOIMINICAN REP

900 800 700 600 Figure 6 Production of farmed Macrobrachium rosenbergii (the FAO 500 data include the categories giant 400 river prawn, freshwater shrimps/ prawns nei and freshwater crusta- 300 ceans nei) in major producing coun- 200 tries in South America in 2001 (mt) 100 (FAO 2003) (Note: FAO data for Brazil has been divided by a factor of ten 0 (see text)). BRAZIL ECUADOR FRENCH GUIANA PERU production is still quite small. A newcomer is the Rate of global expansion Russian Federation, where this species is grown mainly in the heated e¥uent from electric power It is di⁄cult to measure the rate of expansion of fresh- generation. water prawn farming, because of the lack of statistics

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10 Figure 7 Minor production of 0 farmed Macrobrachium rosenbergii (the FAO data include the cate-

GUAM gories giant river prawn, fresh- RÉUNIONSENEGAL water shrimps/prawns nei and MAURITIUS ZIMBABWE FIJI ISLANDS RUSSIAN FED freshwater crustaceans nei) in NEW CALEDONIA other areas in 2001 (mt) (FAO FRENCH POLYNESIA SOLOMON ISLANDS 2003).

400,000 FAO DATA (for M. 350,000 rosenbergii, f/w prawns nei, & f/w crustaceans 300,000 nei) ESTIMATES FOR M. 250,000 nipponense (2000 figure calculated from APR 200,000 1999-2001) TOTAL F/W PRAWNS 150,000

100,000

50,000 Figure 8 Estimated expansion of 0 freshwater prawn farming 1992^ 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2001 (mt).

about the culture of M. nipponense in China. How- and 2001; in other words, production appears to be ever, if we assume that the estimates for that species going up by a factor of over 2.8 annually, a very ex- that have been cited earlier are reasonably accurate, ceptional rate! This shows that, as in the case of we can deduce that over 330 000 mt of all species many other farmed food¢sh species, the inclusion of of Macrobrachium were raised through aquaculture Chinese data distorts the analysis of trends in the rest in the year 2001 (Fig. 8). No doubt there has been of the world. So let us look at the picture after remov- further expansion since that time. The average an- ing the data from China. Without Chinese data, the nual expansion rate (APR) of freshwater prawn farm- APR in the rest of the world over the decade 1992^ ing, if all FAO data and the estimates for M. 2001 was a more modest 11%. However, the expan- nipponense are combined, between 1992 and 2001 sion rate seems to be increasing: in the 2 years from was over 29%. Between1999 and 2001, the global ex- 1999 to 2001it was over 20%. pansion rate was even more rapid (48%). However, So far, in calculating APR, I have included the FAO nearly 83% of the expansion during that whole dec- categories ‘freshwater crustaceans nei’ and ‘fresh- ade and over 85% of the expansion between1999 and water prawns/shrimps nei’ in the ‘all species’ cate- 2001occurred because of the meteoric rise in the re- gories. The main e¡ect of this is to add the large ported farmed production of M. rosenbergii and the estimated production of ‘freshwater crustaceans nei’ estimated output of M. nipponense in China. In parti- in Viet Nam. This category, which is believed to cular, the estimated production of M. nipponense indi- consist principally of M. rosenbergii, contributed cates an APR of nearly 183% year À1 between 1999 12000 mt in1992, over 25000 mt in1999 and about

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1,400,000

1,200,000

1,000,000

800,000

600,000

400,000

200,000

0 Figure 9 Trend in the farmed pro- 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 duction of Macrobrachium rosenbergii, compared with the total for all species Marine shrimp Marine shrimp (no China) of marine shrimp (FAO 2003). M. rosenbergii M. rosenbergii (no China)

28000 mt fromViet Nam to the global all-species ¢g- the world were 11.8% year À1 for freshwater prawns ure for 2001, for example. If we exclude these miscel- and 3.8% year À1 for marine shrimp. laneous (‘nei’) categories and simply look at the FAO data for M. rosenbergii alone, the global expansion À1 ratewasover27%year over the decade1992^2001. Recently published news and If data from China is excluded, the production research results of M. rosenbergii alone still expanded by nearly 12% year À1 in the rest of the world in the decade The literature up to the year 2000 was reviewed by 1992^2001 and increased considerably beyond the New andValenti (2000). Since that time I have endea- decadal average, to over 30% year À1 in 1999^2001. voured to keep up with the research work that has The rapid increase in the expansion of M. rosenbergii been published in international journals and the farming outside China is due mainly to massive ex- news about research results and farming practices pansion in India and a resurgence of production in in various magazines. I have tried to summarize one of the pioneering countries, Thailand. Between this information in the next two sub-sections of this 1999 and 2001, the production of M. rosenbergii in- paper. creased at an annual rate of 86% in India and over 19% in Thailand. The current production of freshwater prawns is News of general interest, 2000^2003 still relatively small, compared with the scale of mar- Bangladesh ine shrimp farming. However, marine shrimp farming has not been expanding so rapidly as is shown in In 2000, Ahmed (2000) reported that 8306 ha were Fig. 9, that has been prepared from FAO data (FAO being used for Macrobrachium culture in Bangladesh, 2003) and includes the two categories ‘freshwater using wild fry,but ACC (2003) reported that the grow- prawns, shrimps nei’ and ‘freshwater crustaceans out area has risen to 40 000 ha. Nandeesha (2001) ‘nei’, but therefore excludes the uno⁄cial estimates reported that over 100 000 small farmers earn most of M. nipponense production. The top line of each pair of their livelihood from culturing freshwater prawns; includes Chinese production; the bottom of each pair however, they still depended on the availability of excludes China. In this ¢gure, the trends for marine wild seed. Some farmers were reported to be stocking shrimp and freshwater prawns look similar. However, wild tiger shrimp (P. m o n o d o n) with wild Macrobra- if you calculate the annual average growth rates, it chium. Penaeus monodon has been grown in low sali- becomes clear that freshwater prawn farming has nities in Thailand and in freshwater in India. been expanding at a much faster rate than marine However, the dangers of this practice have been iden- shrimp, whether China is included or not. Globally, ti¢ed (Fegan 2002). the APR for the decade was 27.4 per year for fresh- Ahmed (2000) reported that freshwater snails water prawns but only 3.9% year À1 for marine were the food of choice by farmers in Bangladesh, shrimp. Excluding China, the APRs for the rest of although that may now have changed.

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Brazil to encourage freshwater prawn farming, using in- puts and technology from Tamil Nadu (Anonymous Moraes-Riodades and Valenti (2001) see a future for 2001c). An earlier phase of the boom in freshwater the intensive production of M. rosenbergii by larger prawn farming in India, mainly in the coastal pro- companies for domestic and export markets and vinces of Tamil Nadu and Andhra Pradesh, was de- small-scale family units (for local use) in the Amazo- scribed by Fegan and Sriram (2001), who reported nia region of Brazil. Small-scale family farms could that it was more pro¢table than sugarcane or rice rear this species, as well as the indigenous (and much production. However, they warned that better pro- sought after) M. amazonicum using more extensive duction e⁄ciency and marketing would be essential technologies for local consumption. as the total production increases and farm-gate prices drop. Jain and Diwan (2002) stated that M. ro- China senbergii can be cultured in waters of 15g L À1 and is In China, the province of Hainan is reported to be im- therefore a suitable species for culture in saline was- porting an improved breed of M. rosenbergii from the telands in India; they also suggested considering M. Charoen Pokphand hatcheries in Thailand (Anon- malcolmsonii, M. idella and M. lamarrei. Commenting ymous 2001d). CP claims that whereas a 30-g aver- that productivity was still quite low in India (an average size is normally achieved, their ‘CPF giant age of 600 kg ha À1 in the year to March 2002), freshwater shrimp’ grow to an average of 100 g for Merican and Vasudevan (2003) noted that about males and 60 g for females (Anonymous 2001e) as 1.2 million ha was available and only about 13% had well as having a 60% meat content (Anonymous been used to date. These authors forecast that Indian 2001f). China is researching M. malcolmsonii as a production of Macrobrachium would rise by about possible replacement for M. rosenbergii (Anonymous 30% per year over the next 2 or 3 years. 2002d). Macrobrachium malcolmsonii is said to grow Two articles by Reddy and Rao (2001a, b) provided faster than the currently cultured freshwater prawn a summary of farming practices in India and con- species in China and is expected to become popular cluded that freshwater prawn farming was poised with consumers. The broodstock was introduced for rapid expansion; however, this potential was from Sri Lanka. An up-to-date review of freshwater being compromised by the high cost of postlarvae prawn farming in China is being presented by Miao (PL) (at that time Rs. 0.75^0.9 each, up to three times Weimin in this symposium, so I will not comment greater than PL of P.monodon). Another summary of on his earlier published paper (Miao & Ge 2002). the expansion of freshwater prawn farming in India was provided by Nagarajan and Chandrasekar Ghana (2002); a typical cost/income scenario was provided for a farm in Andhra Pradesh, which showed an op- The Institute of Aquaculture (Stirling University,Stir- erating pro¢t of over US$ 1000 ha À1crop À1. These ling, UK) is working with M. vollenhovenii in an at- authors reported a lack of export demand in 2002 tempt to encourage the farming of this species in and government restraints on the expansion of the Ghana, where it is indigenous and the subject of arti- industry because of concerns about the excessive sanal activity in roadside markets (Brown 2001). use of groundwater, the potential salinization of agricultural land and the conversion of paddy ¢elds to India prawn farms. Nandeesha (2003) reported that the In the last 3 years, many articles on Macrobrachium polyculture of freshwater prawns with carps has al- farming in India have appeared in international ma- most entirely been replaced by prawn monoculture. gazines; only a few are sampled in this paper, since I He reported that about 22000 ha of ponds were de- am sure that we will hear much more up-to-date in- voted to freshwater prawn culture in the Nellore dis- formation here during our symposium this week. trict of Andhra Pradesh alone. Although hatchery Simple guidelines for freshwater prawn farming raised seed is now available, their quality is variable. in India have been prepared by Saxena (2003). It Selvaraj and Kumar (2003) predicted that fresh- has been reported that Andhra Pradesh produces water prawn production in India could increase to 27000 mt of M. rosenbergii; according to MPEDA, 50 000 mt year À1 by 2010. Several established fresh- this output could be doubled in 2 or 3 years if farmers water prawn farmers and hatchery operators in An- take up this type of farming (Anonymous 2003a).The dhra Pradesh and Tamil Nadu have been promoting government of Haryana was reported to be wishing and assisting similar development in other Indian

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States (Nandeesha 2003; J. Susheela, pers. comm. ymous 2001e).The e¡ect of this programme may ulti- 2004). In a conference held here in Kochi in 2001, mately ¢lter through to the FAO production statistics. a farm-made aquafeed mill in Kuttanad was an- nounced; the freshwater prawn feed produced was Viet Nam said to have reduced feeding costs by 38% and resulted Typically, Macrobrachium have been reared in con- in less non-marketable size animals (Anonymous junction with rice production in Viet Nam, based on 2000, 2001a). Merican and Vasudevan (2003) stated wild fryand little or no feed, achieving low productiv- that local feed companies in India devoted about ity (150^300 kg ha À1crop À1). Now hatchery raised 10^15%of their production capacity to feeds for fresh- PL are more available, many farmers in the Mekong water prawns. Feed production for crustacea is domi- Delta are using both fresh ¢sh and arti¢cial feeds nated by CP,Waterbase, Avanti and Higashimaru. In for 6-month culture periods (leaving another addition there is Hanaqua, Grobest, Godrej and 15 6 months for two crops of rice) to achieve smallercompanies but it was not clear if all these com- 10 00 ^ 150 0 kg ha À1crop À1 (Ridmontri 2002). All panies manufacture freshwater prawn feeds. major seafood processors in the Mekong Delta and some feed companies have become involved in Jamaica hatchery and feed supply for freshwater prawn farm- Macrobrachium farming is proving quite popular in ing, and see processed prawns as an important Jamaica where it is grown in polyculture with tilapia export item. In this country, Proconco is developing (Aiken, Morris, Hanley & Manning 2002). a feed for freshwater prawns and plans to train farmers to run simple hatcheries through its extension Malaysia work (Buranakanonda 2001). Macrobrachium rosenbergii is said to be increasingly popular among consumers of all races in Malaysia Miscellaneous news (Anonymous 2001i). A number of other items of general news were published during the period. These included the report Philippines that freshwater prawns are being considered as a Following 70% survival rates in the (government) candidate species for an organic label in Asia (INFO- hatchery phase, batches of freshwater prawn PL are FISH 2002). Interest in farming other species has being distributed to the private sector in the Philip- been reported. Nandeesha (2003) reported that there pines; polyculture with tilapia is being favoured was commercial potential in rearing M. malcolmsonii (Anonymous 2001g). Macrobrachium rosenbergii was in both India and China. Moraes-Riodades andValen- even being promoted for culture in metal drums in ti (2001) also see a future for the culture of M. amazo- urban areas (Anonymous 2001h). nicum in the Amazonia region of Brazil.

Paci¢c News of scienti¢c and research importance, 2000^2003 Freshwater prawns were included in the eight species selected as having the most potential for culture in Biology the Paci¢c region (Anonymous 2002a). A useful book for the shelves of taxonomists on the biology of palaemonid prawns has been provided by Russia Jayachandaran (2001) and reviewed by New (2002b). Freshwater prawns are being produced in one farm One hundred and forty-four pages are devoted to in Russia, which produced 6 mt in 2000. Most is sold Macrobrachium spp. More than 180 valid species are in Moscow but some in the location of the farm, As- now recognized, far more than the 125 species men- trakhan (Anonymous 2001b); investment was being tioned by Holthuis (1980). Another useful book is on sought to enlarge capacity. the biology of decapod larvae (Anger 2001).

Thailand Breeding, genetics and sex reversal CP was said to be planning a major expansion in Research work on the breeding, genetics and sex re- freshwater prawn production in Thailand (Anon- versal of Macrobrachium spp. in the past 3 years has

r 2005 Blackwell Publishing Ltd, Aquaculture Research, 36, 210^230 217 Overview of freshwater prawn culture in USA MBNew Aquaculture Research, 2005, 36, 210^230 been active. In a recent review article on the genetic portance of comparative work on the various strains improvement of freshwater prawns, whose published of freshwater prawns, and the potential improvement reference list is unfortunately incomplete, Lutz that could be gained not only from selection and (2003) states that spermatophore microinjection ap- cross breeding but also, perhaps, from examining pears to be aviable means of introducing genetic con- whether di¡erent strains have di¡erent rearing re- structs into Macrobrachium species. Gene transfer quirements. may therefore complement the promise of ‘conven- Working with M. australiense, Dimmock, William- tional’selection and hybridization as a means of im- son and Mather (2002) have found that there is as proving performance in freshwater prawn culture. much trait variation within geographical regions as According to this author, the most important traits between di¡erent regions. This variation seems to be that might be improved are, in addition to growth related to environmental factors (e.g. abdomen size rate, cold tolerance, the duration of larval develop- correlates with increased habitat structure). Manipu- ment and the tolerance of reduced salinity during lating temperature reinforces environmental in£u- the larval cycle. An Indo-Norwegian consultation in ences on morphology in this species. Breeding work Mumbai in 2001identi¢ed the need for collaboration (perhaps with other Macrobrachium spp. also) should between Indian national research institutions and take local habitat characteristics into consideration. AKVAFORSK on the genetic improvement of fresh- Chinese scientists have successfullycrossed female water prawns (Anonymous 2002b). It would be inter- M. nipponense with male M. hainanense (Anonymous esting to hear if this collaboration has commenced. 2002c; H. Fu, pers. comm. 2002). Isozyme analysis Baghel and Saxena (2001) proposed a number of con¢rmed that the hybrids possessed both maternal biotechnological tools to enhance freshwater prawn and paternal genes. Of the ¢ve single pair crosses, production. These included chromosomal engineer- four spawned and three hatched hybrids (the other ing, molecular genetics, genetic engineering and tis- aborted). The hatching rate of the hybrids was over sue culture engineering. Noting that freshwater 90% and the survival rate to PL was 20^60%. prawns were less susceptible to the white spot syn- In a study providing preliminary information for drome virus than marine shrimp, these authors be- those seeking to produce hybrids, Graziani, De Dona- lieve that gene transfer should be used to produce to, Lodeiros, Orta and Salazar (2001) found that, of strains having a growth hormone gene construct. the four species considered, the closest genetic dis- Sterile M. rosenbergii can be produced when juve- tances were between M. carcinus and M. rosenbergii niles are irradiated at 1.0 and 1.5 krad using g radia- and the most genetically distinct were M. acanthurus tion from cobalt-60 (Lee & Tiersch 2001).When adult, and M. amazonicum. Leucilaminopeptidase (LAP) these irradiated females did not produce eggs, or pro- and Peptidase II (PEPII) can be used to detect the pre- duced less than100 eggs that were dropped within 4 sence of hybrids among these species. days. Irradiated males were shown to produce no, or Several institutes in Israel, Thailand and the UK reduced sperm, and failed to fertilize the eggs of non- are working with sex-reversed prawns (Anonymous irradiated females. 2000^2001; Brown 2001, 2002; Buranakanonda Buranakanonda (2002) reported that there were 2002) but I have not yet seen any peer-reviewed pub- three major strains (one a cross-bred strain) of fresh- lication on their results. water prawns in Thailand and that Kasetsart Univer- Cavalli, Lavens and Sorgeloos (2001) showed that sity had found that the Myanmar prawns from the under proper rearing conditions, M. rosenbergii fe- Yapil River were the meatiest. This university has in- males are able to spawn up to ¢ve times within a stituted a breeding programme, using this strain to 180-day period, compared with three to ¢ve times as select for good fecundity and survival, as well as reported for wild populations. Indicating that the smaller claws and heads. I believe that it is possible number of viable larvae produced might be increased that this work has been done in conjunction with CP by in vitro incubation, these authors discuss the con- (see earlier). straints to this technique; disinfecting the eggs may Bart and Yen (2001) reported that PL survival (up be necessary to replace the loss of the anti-microbial to 36 days) was much higher (33%) when broodstock secretions of the incubating female. M. rosenbergii from Thailand were used instead of It is well known that increasing the salinity that those fromViet Nam (o2%). Furthermore, cross bred adult females are kept in enhances hatchability; com- Thai females andViet Nam males resulted in an even monly they are kept at 5 g L À1. Recently Cheng, Liu, higher PL survival (39%). This work indicates the im- Cheng and Chen (2003) have shown that both male

218 r 2005 Blackwell Publishing Ltd, Aquaculture Research, 36, 210^230 Aquaculture Research, 2005, 36, 210^230 Overview of freshwater prawn culture in USA MBNew and female adult prawns (M. rosenbergii)canadaptto rearing of freshwater prawns in India and the treat- a salinity of 14g L À1 within 2 days. Since this is the ment used to counter them. The problems included commonly used salinity for rearing larvae of this white muscle or idiopathic muscle necrosis, ciliate in- species, this ¢nding could simplify hatchery opera- festations, antenna and tail rot, soft shell, hard shell tion. Law,Wong and Abol-Muna¢ (2002) found that and low dissolved oxygen. M. rosenbergii egg hatchability is extremely sensitive Cheng and Chen (2002) found that M. rosenbergii to hydrogen ion concentration in brackish water. At (size not stated) reared at high temperatures (33^ À1 12 g L , the highest hatching rate (92.22%) was de- 34 1C), high pH (9.0^9.5), low pH (4.6^5.0), low DO2 tected at pH 7.0. However, at pH 6.5 and 7.5, hatching (1.75^2.75 mg L À1) and exposed to ammonia-N rates markedly fell to 5.00% and 13.33% respectively. (0.55 mg L À1) and copper sulphate (0.2 mg L À1)ex- Hatching rates at pH 5.0, 8.0, 9.0 and 10.0 were zero. perienced a decrease in phenoloxidase activity, lead- This important study indicates that careful control ing to a reduction in their immune response and of the pH of the brackish water used to hatch M. ro- susceptibility to Lactococcus garvieae infection. This senbergii would increase hatching success, reduce the pathogen, together with the yeast-like Debaryomyces number of broodstock needed and (perhaps most im- hansenii and Metschnikowia bicuspidata,hascaused portantly) reduce hatchery production costs. It is not many disease outbreaks inTaiwan. yet known whether other species of Macrobrachium Cheng and colleagues (2003) noted that experi- are so sensitive to pH at the time of hatching. mental challenge of freshwater prawns by the injec- The availability of cryopreserved larvae could tion of bacteria and subsquent exposure to di¡erent greatly assist in facilitating stock distribution where salinity levels has shown that 5 and10g L À1 appears lack of hatchery-reared animals hampers the expan- to have a favourable e¡ect on survival; Taiwanese sion of freshwater prawn farming. Pillai, Rao and farmers are therefore likely to add brine to grow-out Mohanty (2001) measured the toxicity of various ponds. cryoprotectants ^ dimethyl sulphoxide (DMSO), Goswami and Prasad (2000) have found that ben- methanol, glycerol and ethylene glycol ^ on the ¢rst zalkonium chloride (BKC) can be used as an e¡ective zoeal stages of M. rosenbergii. Methanol was found to anti-bacterial and immunostimulant for M. rosenber- be the most toxic, followed by DMSO. Larvae could be gii. These authors reported that the minimum lethal safely exposed to these cryoprotectants for 20 min at concentration for the several bacteria tested ranged 20 1C at up to 10% v/v. Multiple cryoprotectants (a from 1.0 to 1.5 ppm. Despite the fact that Liao and mixture of these substances) were found to be less Guo (1990) had reported that the tolerance to BKC of toxic than single substances. this species was 2 ppm in 24 h, Goswami and Prasad

(2000) found the 24-h LD50 for 2-month old M. rosenbergii (weight not indicated) to be 10ppm. Some cau- Diseases, prophylaxis and the use of tion in its use seems to be indicated until further immunostimulants studies are reported. Several papers on the diseases of freshwater prawns, The Taura Syndrome (TSV-like) virus that is com- on prophylaxis, and the use of immunostimulants mon in P.vannamei has not been found in freshwater have been published. In a study over a larval rearing prawns (Anonymous 2003b). cycle of M. rosenbergii by Phatarpekar, Kenkre, Sree- pada, Desai and Achuthankutty (2002), the bacterial £ora was predominantly Gram-negative (75% of the Experimental techniques total isolated strains). Aeromonas, Alcaligenes and Pseudomonas were the most frequently observed gen- A development in experimental technique has been era in the water but Alcaligenes, Enterobacteriacae, noted. The Institute of Aquaculture (Stirling Univer- Pseudomonas and Streptococcus were the most abun- sity, Stirling, UK) has shown that it is possible not dant on the larvae themselves.Vibrio spp. were found only to tag the very smallest PL M. rosenbergii but in eggs and water but were completely absent in lar- also pre-metamorphic larvae (Anonymous 2000^ vae. The bacterial £ora of eggs resembled the water 2001). Describing this technique in detail, Brown, but a distinctly di¡erent population was associated McCauley, Ross, Taylor and Huntingford (2003) con- with the larvae. cluded that VI elastomer tags (a coloured liquid that Nagarajan and Chandrasekar (2002) reported cures to a £exible solid after injection under the epi- some of the common problems encountered in the dermis and £uoresces under UV light) could be used

r 2005 Blackwell Publishing Ltd, Aquaculture Research, 36, 210^230 219 Overview of freshwater prawn culture in USA MBNew Aquaculture Research, 2005, 36, 210^230 to mark small numbers of individual larval and im- juveniles. Further research on this topic is necessary mediately PL prawns and that VI alphanumeric tags before pre-stocking batch-grading can be truly e¡ec- (small biocompatible plastic labels with unique codes tive in maximizing production and revenue from that are inserted beneath transparent regions of skin) freshwater prawn farming. could be used to mark an unlimited number of indivi- According to D’Abramo, Daniels, Gerard, Jun and duals with a size of approximately 0.5 g. Summerlin (2000), strategies that avoid achieving the critical standing crop that induces what is apparentlya chemical-mediated growth reduction are necessary. Management, including the use of substrates These could include selective harvesting or stock ma- Several papers on nurseryand grow-out management nipulation and movement. These authors were also have been published. Marques, Lombardi and Boock able to demonstrate an important feature of immediate (2000) found that high-density nursery culture bene¢t to commercial culture in special marketing (either 10PL L À1 for a primary phase using 0.011g conditions such as the temperate-zone culture of fresh- early metamorphosed animals, or 800 PL m À 2 in a water prawns ^ a density threshold that could be used secondary phase stocking the results of the primary to reduce growth rates and therefore adjust production phase as 0.053g PL) of M. rosenbergii in cages within to suit the best time for marketing. Reductions in an earthen pond seems feasible as a means of redu- weight gain began to occur when a critical biomass cing nursery phase costs.Van Arnum,Tidwell, Coyle, density of approximately 500 mg L À1 was attained. Vitatoe and McCathy (2001) reported that, under in- Alston and Garc|¤a-Pe¤ rez (2001), studying the poly- door nursery conditions, 0.04 g PL M. rosenbergii culture of tilapia stocked at 1m À 2 and freshwater stocked at 430 PL m À 2 had a signi¢cantly better sur- prawns at 5 m À 2, found that removing all female vival rate (76% over 60 days) with continuous light prawns during each monthly partial harvest over a (L24:D0) than with either L12:D12 (59%) or L0:D24 19-month period increased the numbers of market- (58%). No comment on the light intensity or its spec- able prawns but did not a¡ect mean weight (40 g). tral quality was mentioned in this abstract. Research on the use of substrates to increase pro- Ranjeet and Kurup (2002a), in a paper on hetero- duction in freshwater prawn grow-out systems has genous individual growth (HIG) mentioned the pos- continued in the USA and is beginning to be applied sibility that di¡erential growth could have a genetic in small-scale commercial practice. Tidwell and his basis. The work of Sun,Weatherby, Dunlap, Arakaki, co-workers in Kentucky have published a series of pa- Zacarias and Malecha (2000) indicates that there are pers (Tidwell, Coyle, Van Arnum & Weibel 2000a; substantial di¡erences in the androgenic gland (AG) Tidwell, Coyle,Van Arnum,Weibel & D’Abramo 2001; protein content, SDS-PAGE polypeptide pro¢le and Tidwell, Coyle,Van Arnum & Weibel 2002) on the use cellular morphology between the OC, OBC and BC of substrates consisting of 120-cm-wide panels of male morphotypes of M. rosenbergii; this ¢nding polyethylene ‘construction safety fencing’ material, may be a further indication that HIG has genetic as placed in rearing ponds either horizontally or verti- well as social associations. For the moment, however, cally to increase the surface area available to prawns. Ranjeet and Kurup (2002a) have stressed the impor- This material is illustrated in Tidwell and D’Abramo tance of careful grow-out management in commer- (2000) and New (2002a). In one of their most recent cial farms to maximize the yield of marketable papers,Tidwell and colleagures (2002) reported that prawns and synchronize their availability with mar- they had obtained a signi¢cantly increased produc- ket requirements. An excellent review on the man- tion rate of freshwater prawns (2653 kg ha À1) when agement of size review has been provided by the surface area was increased by 100% compared Karplus, Malecha and Sagi (2000). Ranjeet and Kur- with a control with no substrate (2140 kg ha À1)in up (2002b) found that the trend for M. rosenbergii lar- an experiment lasting106 days where 0.2-g juveniles vae that hatch ¢rst to be weaker and take longer to were stocked at 65000 ha À1.Higheraverage¢nal reach metamorphosis appeared to continue into the weights were obtained when substrates were used. grow-out phase. However, these ¢ndings are in con- An intermediate production level between these ex- trast to the results of Zacarias (1986) as reviewed by tremes was achieved with half the quantity of addi- Karplus and colleagues (2000). Using genetically tional substrate but, at this level, it made no marked populations, Zacarias (1986) showed that di¡erence whether the substrate was hung vertically early-hatching larvae are likely to become early-set- or horizontally.Vertically hung substrates are easier tling PL, which, in turn are likely to become larger to install and maintain and o¡er the possibility of

220 r 2005 Blackwell Publishing Ltd, Aquaculture Research, 36, 210^230 Aquaculture Research, 2005, 36, 210^230 Overview of freshwater prawn culture in USA MBNew increasing surface area even more than 100%, and on nutrition and feeding. Coyle and Tidwell (2002) therefore the potential of greater production. suggested that more research should be carried out On the other hand, Posadas, Walters and Long on management practices that maximize the avail- (2003), reporting a 120-day experiment where sur- ability of natural food. ‘Phase feeding’, where diets face area was increased over no-substrate controls with increasing protein levels are applied during the by 100%, using similar vertical substrates and juve- production cycles were suggested; the use of a low niles stocked at 50630 ha À1, found no signi¢cant protein‘fertilizer’diet for the ¢rst month, followed by e¡ect on survival rate, harvest size or count, yield a 28% protein steam pelleted diet for the next 6 or feed conversion. However, the average yield weeks and a 40% protein diet for the ¢nal 4 weeks of (1497 kg ha À1) obtained by Posadas and colleagues rearing were used in one trial.This is contrary to nor- (2003) was markedly lower than those achieved mal practice (lowering protein levels as animals by Tidwell and colleagues (2002). More detailed become older) but was suggested as a means of comparison between these two experiments is neces- providing more and better nutrition when natural sary, to see what experimental parameters di¡ered, foods become grazed down. Further trials described before further research con¢rms the obvious ad- by Coyle and Tidwell (2003) compared phase feeding vantages that Tidwell and colleagues (2002) have with the use of a 32% diet (similar to a cat¢sh feed found in adding substrates to freshwater rearing formulation) throughout the rearing cycle. No di¡er- ponds. ences in total production or average prawn weight D’Abramo and colleagues (2000), studying the ef- were observed; however, phase feeding resulted in a fects of combinations of water volume, bottom surface 20% increase in the number of animals weighing area and water replacement rate on weight gain of ju- over 30 g. In each trial feeding rates were 20% higher venile M. rosenbergii, have highlighted the impor- than normal and stocking densities were relatively tance of allowing for maximum density-independent high (6.5 and 7.9 m À 2). Phase feeding using a marine growth of animals for all treatments in experimental shrimp diet also increased feeding costs, so careful work with crustaceans that uses growth as a re- economic and marketing considerations need to be sponse variable to compare performance on di¡erent made in applying such research ¢ndings. diets. Greater weight gain was achieved under both Correia, Pereira, Silva, Horowitz and Horowitz greater water volume and bottom surface area. In- (2003) found that increasing the natural productivity creased water replacement did not compensate for of ponds signi¢cantly improves feed conversion ratio, lower water volume. Increasing available surface area with concomitant savings in farm operating costs. makes it possible to reduce the water replacement Fertilization made it possible to reduce feeding rates rate. This work is therefore important for moving to- by up to 50% with no reduction in yield. In this case, wards zero-exchange grow-out systems. the authors used an average of 2.5 kg of lime,110g of Vitatoe, Tidwell, Coyle and Van Arnum (2000) re- simple superphosphate and 340 g of ammonium sul- ported that menhaden ¢sh oil could be used as a suc- phate per 50 m2 pond every 2 weeks (in practice, ap- cessful alternative to petroleum products such as oil plication rates were adjusted on the basis of water- and diesel fuel for eliminating the air-breathing in- quality analysis) during an 84-day trial. Full feeding sects that predate on small, newly stocked freshwater was compared with a reduction of 50% throughout prawn juveniles. Not only does this promote environ- the trial and a treatment that consisted of feeding mental safety and comply with organic certi¢cation 0%, 25% and 50% of the control feed for the three but it eliminates the possibility that juvenile prawns subsequent periods of 28 days. The latter treatment may consume toxic petroleum droplets after stock- resulted in prawns that were smaller than market ing. These workers stated that menhaden ¢sh oil size and a much reduced total net yield. However, a applied at 1.6 gallons (US) per surface acre reduction of 50% in feeding rate gave similar ¢nal ( 15 L ha À1) was not only e¡ective in controlling weights and yield. air-breathing insects but also cost-e¡ective in com- A successful semi-synthetic broodstock diet (44% parison with petroleum-based products. protein,9% lipid) for M. rosenbergii was used in reproductive performance trials by Cavalli and colleagues (2001). The formulation included, inter alia,casein, Nutrition and feeding lobster meal, soy protein isolate, squid meal, shrimp Besides genetics, the major area of research publica- meal, crab meal, synthetic amino acids, soybean oil, tion on Macrobrachium in the past 3 years has been ¢sh oil, a protein extract attractant, astaxanthin, soy

r 2005 Blackwell Publishing Ltd, Aquaculture Research, 36, 210^230 221 Overview of freshwater prawn culture in USA MBNew Aquaculture Research, 2005, 36, 210^230 lecithin, vitamins and minerals, together with a car- harvest. In the second series of ponds, the pelletized rageenan binder and anti-oxidants. cat¢sh feed was applied for the second 30 days of Roustaian, Kamaruddin, Omar, Saad and Ahmad rearing, followed by an extruded 35% protein cat¢sh (2001) have demonstrated the importance of lipid as feed for the ¢nal 60 days. The third series of ponds the major metabolic energy source for growing lar- was treated similarly during the second 30-day peri- vae of M. rosenbergii and postulated that research on od but an extruded 40% protein sinking marine the e¡ects of the lipid composition of broodstock diets shrimp feed was used for the ¢nal 60 days. Finally,in would be bene¢cial. Roustaian, Kamaruddin, Omar, the fourth series of ponds, a 35% protein marine Saad and Ahmad (2000) found that the amino acid shrimp feed was applied from day 31for the next 90 composition of M. rosenbergii larvae appeared to be days. Although yields were not signi¢cantly di¡erent, relatively unchanged during larval stages I^IX, sug- the highest (1183 kg ha À1) was achieved by the con- gesting that their dietary amino acid requirements trol (sinking 32% cat¢sh feed from day 31to harvest). could be satis¢ed by a feed having a similar amino The authors concluded that dietary protein level had acid pro¢le to the larvae themselves. D’Abramo no appreciable e¡ect on yield, survival, feed conver- (2002) reported the successful development of a for- sion or ¢nal average prawn count (about 22 kg À1). mulated microbound feed to replace the use of Arte- However, FCR in all treatments was rather poor mia for larval stages V^XI and for PL M. rosenbergii. (3.0^4.1:1). No information on the analysis of the var- The formulated diet was moist (60% moisture) and ious feeds was presented; thus, no comparison of the could not be reduced to particles below 0.25 mm un- protein/energy ratios was feasible. It is possible that less previously dried.The diet was energy dense (46% the dietary protein levels of all treatments in this trial protein and 37% lipid). Although experimentally suc- were unnecessarily high. D’Abramo and New (2000) cessful, as far as I know its use under commercial reported the use of commercial freshwater prawns hatchery conditions has not yet been reported; its feeds with protein levels ranging from 22% to 38.5% unit cost was also not stated in this paper. and that, where natural food was also available, sev- Niu, Lee, Goshima and Nakao (2003) found that eral trials have reported success with diets having the food consumption of M. rosenbergii PL distinctly protein levels as low as13% or14%. increases with temperature (23^33 1C) and is posi- Ali and Sahu (2002) found that the use of fermen- tively related to initial body weight (7^38 mg). Models ted ¢sh silage as a feed ingredient showed better (but were constructed to relate maximum food consump- not statistically signi¢cant) weight gain, FCR and tion and speci¢c growth rate with water temperature PER than freshwater prawns fed 35% protein/8% li- and initial size; these could be used to predict the pid diets containing ¢sh meal or acid ¢sh silage. food requirements and growth of PL in aquaculture. GonzaŁ lez-Pena, Gomes and Moreira (2002) showed In an experiment where a series of diets contain- that the speci¢c growth rates, feed e⁄ciency conver- ing varying amounts of trash ¢sh meal and ground- sion and protein e⁄ciency ratios of small and large nut oil cake with level amounts of shrimp head meal adult M. rosenbergii improved as levels of dietary ¢bre and coconut oil cake were fed to 0.27 g initial weight were increased (substituting cellulose for starch in M. rosenbergii and reared for 30 days, Hari and Kurup semi-puri¢ed diets) from 0.4% to 8%; they concluded (2003) found that highest growth rate and maximum that the inclusion of up to 10% of dietary ¢bre in- protein utilization was obtained with a 30% protein creases growth rates in adult prawns by increasing level. In a subsequent experiment using four diets nutrient residence time, thus increasing absorption. with this protein level, these authors showed that it Mendoza, Montemayor, Aguilera,Verde and Rodr|¤- was possible to achieve similar results as trash ¢sh guez (2001) found signi¢cant attractive properties meal was gradually replaced by groundnut oil cake, when arginine, cadaverine, freeze-dried red crab ex- thus indicating the potential for dietary cost savings. tract and coconut extracts were added to a commer- Posadas, Walters and Long (2001) and Posadas, cial diet for M. rosenbergii. Research has shown that Walters and Long (2002) compared di¡erent feeds anti-nutritional tannins a¡ect M. rosenbergii far less and feeding regimes for the grow-out of M. rosenber- than ¢sh (Anonymous1999^2000). gii in Mississippi. A daily ration of cottonseed (ap- Using ascorbyl 2 polyphosphate, Hari and Kurup proximately 3.7kg ha À1) was applied to all four (2002) found that dietary vitamin C levels have a per- treatments for the ¢rst 30 days of rearing. In the con- ceptible in£uence on the survival of M. rosenbergii trol ponds, a sinking pelletized 32% protein cat¢sh juveniles and recommended an inclusion rate of feed was fed from day 31 for the next 90 days to 135 mg kg À1 of ascorbic acid equivalent.

222 r 2005 Blackwell Publishing Ltd, Aquaculture Research, 36, 210^230 Aquaculture Research, 2005, 36, 210^230 Overview of freshwater prawn culture in USA MBNew

Available surface area can be increased by introdu- monoculture and 55 grew prawns in polyculture cing arti¢cial substrates, as shown by the continuing with Indian major carps such as catla (Catla catla) work of Tidwell and colleagues (2000a, 2001, 2002). and rohu (Labeo rohita), and grass carp (Ctenopharyn- The latter authors have demonstrated that increasing godon idella). Comparing monoculture with polycul- substrate increases production and improves feed ef- ture, these authors reported yields of 95^1297 kg ¢ciency. ha À1 of prawns in monoculture, compared with 70^ 493 kg ha À1of prawns and 200^1200 kg ha À1of ¢sh in polyculture. Revenue generation indicated that Polyculture monoculture was generally more advisable than The polyculture of freshwater prawns with other spe- polyculture in this situation. The ¢nal conclusion cies continues to attract research interest. In Brazil, was that freshwater prawn culture was a useful way Dos Santos andValenti (2002) have shown that stock- of increasing income and employment where double ing densities of up to 6 m À 2 M. rosenbergii PL did not cropping of rice was not possible because of monsoon a¡ect the production of tilapia (Oreochromis niloticus) £ooding. Kurup, Ranjeet and Hari (2002) provide stocked at1m À 2 over a175-day experimental period, further information con¢rming this matter, describ- and required neither additional feeding nor signi¢- ing it as an‘eco-friendly’ form of aquaculture. cant changes in management. At the highest prawn stocking rate, 3721kg ha À1of tilapia (¢nal average Transport survival we ight 519.6 g) and 818 kg ha À1of prawns (¢nal average weight14.7 g) were obtained. Lower prawn stock- The important topic of the survival of prawns during ing rates achieved larger ¢nal average prawn weights transport from one location to another has also (34gat2mÀ 2 and23gat4mÀ 2). Achieving addi- attracted research attention. Juvenile prawns are tional yield without additional feed improves the sus- usually transported in plastic bags ¢lled with water tainabilityof the system. In Puerto Rico Garc|¤a-Pe¤ rez, and air or oxygen, often inside styrofoam coolers. Alston and Corte¤ s-Maldonado (2000) had stocked Frequently, losses are experienced because of dete- one 7^8 g tilapia m À 2, with or without juvenile riorating water quality and stress. Coyle,Tidwell,Van prawns (1.0^1.3 g) at 7 m À 2, and compared with Arnum andWeibel (2000) reported the e¡ects of den- prawns alone at 7 m À 2, in an experiment lasting sity on survival and associated water quality para- about145 days.The feeding rate was adjusted accord- meters, transporting animals at 10, 25 and 50 g L À1 ing to the mean biomass. This work showed that this (since they were using 0.26-g animals, this was form of polyculture has the potential of maintaining equivalent to approximately 38, 96 and 192 in- the yield of tilapia production at non-signi¢cantly dif- dividuals L À1). Their ¢ndings were that although to- ferent levels (2942 kg ha À1, in monoculture and tal and unionized ammonia concentrations (and to a 2769 kg ha À1 in polyculture) with similar average ¢- lesser extent nitrite levels) increased with density, nal weights. However, while 1367 kg ha À1 of prawns they were not considered to reach lethal levels at the was obtained in monoculture, this fell to 951kg ha À1 temperature (22 1C) and pH (average 8.1) conditions in polyculture. Furthermore, the mean weights of the used, up to the highest stocking transport density prawns were signi¢cantly di¡erent (55 g in monocul- (50 g L À1). The signi¢cantly lower survival levels ture and 31g in polyculture). It would have been in- when prawns were transported at 50 and 25 g L À1, teresting to compare the results of these two papers compared with 10g L À1 were attributed to reduced further if Dos Santos andValenti (2002) had included dissolved oxygen levels at higher transport densities. À1 a treatment where prawns were stocked alone. After 8 h, DO2 was 3.2 ppm at 10 g L , but only The work of Tidwell, Coyle,Van Arnum,Weibel and 1.6 ppm at 25 g L À1 and 1.3ppm at 50 g L À1.

Harkins (2000b) suggests that rearing tilapia (O. nilo- Although juveniles can tolerate DO2 levels as low as ticus) with M. rosenbergii may improve overall pond 1.0 ppm for short periods, the levels found in this e⁄ciency. In this experiment, tilapias were grown in study were likely to cause stress. Recommending that cages attached to a £oating deck at the deep end of juveniles should not be transported at densities in ex- the pond. cess of 10g L À1 (e.g. about 38 individuals weighing Kurup and Ranjeet (2002) surveyed 122 farms in 0.26 g) in sealed containers when the transport time 1998^2001in Kuttanad, India (the‘rice bowl’of Kera- was eight or more hours, these researchers noted that la); 75 used polders for M. rosenbergii culture, al- higher transport temperatures would certainly in- ternating with rice. Twenty farms practised crease oxygen consumption and nitrogen excretion,

r 2005 Blackwell Publishing Ltd, Aquaculture Research, 36, 210^230 223 Overview of freshwater prawn culture in USA MBNew Aquaculture Research, 2005, 36, 210^230 making further reductions in transport density es- production in India and Bangladesh will markedly sential. In terms of numbers these transport density increase, mainly of M. rosenbergii, for both domes- recommendations seem much lower than those re- tic and global markets; ported or suggested by other authors for young the output of Thailand will expand signi¢cantly,as PL. For example, densities in closed containers of the country realizes that a global market is becom- 250^417 L À1 for short transport times in Brazil and ing available and that the culture of freshwater 666 L À1 for 24^36 h in Thailand were cited by Cor- prawns may be more environmentally acceptable reia, Suwannatous and New (2000); 100 L À1 when than marine shrimp; plastic straw was included as a transport habitat by Brazil will become a signi¢cant producer of both Vadhyar, Nair, Singh and Joshi (1992); 125^250 L À1 M. rosenbergii and M. amazonicum; for up to 16h by Valenti and New (2000); and 250^ other Latin American and African countries will 400 L À1 for up to 16h by New (2002a). However, increase their activity in this ¢eld; since young PL only weigh approximately 0.01g Research on the culture of freshwater prawns in each, these densities all fall well within the maxi- temperate zones, pioneered in the USA, will be- mum transport density by weight recommended by come utilized in the temperate zones of other Coyle and colleagues (2000). Thus 10g L À1 could be countries; recommended as a general maximum transport den- markets for freshwater prawns will continue to sity for PL and juveniles but, for practical purposes, it expand in both industrialized and developing would be more useful to know the numbers, rather countries. than the weight, per unit volume. Larger animals (including broodstock) are also sometimes transported long distances. This topic therefore needs further elu- Future scale of production cidation, so that practical tables could be derived, which would state the number of animals recom- In considering the e¡ects of these expectations on mended for di¡erent animal weights, under various the global output of farmed freshwater prawns, I have levels of temperature and pH, and for varying trans- initially ignored the largest producer, China, partly port times. because such a large proportion of its total production in the last 3 years (namely that contributed by the indigenous species M. nipponense)isonlyanesti- mate. This, in addition to the very rapid expansion in A glance into the future of freshwater farmed M. rosenbergii production reported to FAO be- prawn farming tween 1996, when it suddenly reported an output of Forecasting the future is little more than gazing into over 37000 mt, and 2001, when an output of over a telescope and expecting. However, it is di⁄cult to 128000 mt was reported, totally skews any global resist the temptation. picture. It is extremely di⁄cult to make meaningful global forecasts if China is included. However, I will try! Let us look at the possible future in the world ex- Characteristics of the sector cluding China ¢rst. As noted earlier in this review, In looking at global trends over the period from now the average expansion rates for M. rosenbergii in the until 2006, I would expect that: world outside China were between about 12% and Chinese production of M. nipponense will continue 30% yr À1, depending on whether we consider the to increase, for its domestic market and (hopefully) whole decade from 1992 to 2001, or consider only China will commence declaring its production of the period 1999^2001. It would probably be over-op- this species in its statistical returns to FAO; timistic to imagine that freshwater prawn farming Chinese production of M. rosenbergii will expand would continue to expand at 30% year À1 in the fu- and this species will become an export product; ture! However, even if the more modest expansion China may develop commercial farming of M. mal- rate experienced between 1992 and 2001 continues colmsonii and (perhaps) of M. amazonicum,which for the rest of the current decade, global production is larger than M. nipponense, but is still more (excluding China) will be signi¢cantly greater by likely to appeal to the domestic market than 2010. Figure10 shows that continued average expan- M. rosenbergii; sion rates at 12% year À1 would result in a global

224 r 2005 Blackwell Publishing Ltd, Aquaculture Research, 36, 210^230 Aquaculture Research, 2005, 36, 210^230 Overview of freshwater prawn culture in USA MBNew

700,000

BASED ON 1992-2001 600,000 GROWTH RATE (12% / yr) 500,000 BASED ON 1999-2001 GROWTH RATE (APR 30% /yr) 400,000

300,000

200,000 Figure 10 Estimates (mt) of future production of farmed Macrobra- 100,000 chium rosenbergii (excluding Chinese and ‘nei’ production) in the current 0 decade. 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

800,000

M. rosenbergii (excluding China) 700,000 Other species and Chinese production added 600,000 TOTAL

500,000

400,000

300,000

Figure 11 Estimate (mt) of the fu- 200,000 ture production trend based on a doubling of Chinese and‘nei’production between 2001 and 2010 and 100,000 a 12% annual expansion rate for Macrobrachium rosenbergii in the rest 0 of the world. 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 farmed output of M. rosenbergii alone of over their output as M. rosenbergii (the nei categories) may 159000 mt by 2010. The estimate shown in Fig. 10 also double between 2001and 2010. If this happens, not only excludes the potential production from Chi- and production in the rest of the world expands at na but also the production of other Macrobrachium 12% year À1 (the same as in the decade 1992^2001), spp. and the production of Viet Nam, which is cur- the total output of freshwater prawns by the end of rently ‘lost’within the FAO category ‘freshwater crus- this decade would exceed 700 000 mt year À1 ( Fig. 11). taceans nei’. Figure 12 shows what would happen if Chinese So now let us look at what may happen if we in- and Vietnamese production trebled and the exclude potential growth of the sector in China andViet pansion rate in the rest of the world continued Nam. It is entirely possible that the output of M. ro- at 30% year^1, the rate achieved between 1999 senbergii and M. nipponense in China in 2010 will be and 2001. If that happened the global production of double that in 2001 (which would result in a produc- freshwater prawns would reach over 1.4 million - tion approaching 500 000 mt) and that the assumed mt year À1 by 2010. production of M. rosenbergii in Viet Nam and other This then is the potential picture. Based on a dou- minor producing countries not speci¢cally reporting bling or trebling of output in China and Viet Nam

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1,600,000 M. rosenbergii (excluding 1,400,000 China) 1,200,000 Other species and Chinese production 1,000,000 added TOTAL 800,000 Figure 12 Estimate (mt) of the future 600,000 production trend based on a trebling 400,000 of Chinese and ‘nei’ production between 2001 and 2010 and a 30% 200,000 annual expansion rate for Macrobra- 0 chium rosenbergii in the rest of the 2001 2002 2003 2004 2005 2006 2007 2008 20092010 0 world. and continuing expansion rates of between 12% and desirable traits or (if consumers will accept it) by 30% year À1 in the rest of the world, the farmed pro- gene manipulation and transfer is essential to im- duction of Macrobrachium spp. would be between prove the viability of freshwater prawn farming. 700 000 and 1.4 million mt by 2010. In these scenar- Further work on hybridization to combine the at- ios, the potential production of other Macrobrachium tractive traits of various species is also warranted. spp., such as M. malcolmsonii, M. vollenhovenii and For example, it may be possible to combine the de- M. amazonicum have not been considered. licate £avour of one species, which commands a Being cautious myself, I would expect that total premium price, with the more rapid growth rate global freshwater prawn production will be in the re- and/or ¢nal market size of another. gion of 750 000^1000 000 mt year À1 by the end of Genotype/phenotype e¡ects on HIG need much the current decade. This would place its production more elucidation. Knowledge on this topic is prob- almost in the same order of magnitude as the marine ably a prerequisite for successful selection, im- shrimp farming sector now but, of course, entirely proved management, and enhanced pro¢tability. di¡erent in its characteristics. I have often remarked that there should be less research on the hatchery phase of species of ¢sh and crustacea, where so much is already known and successful hatchery technologies exist and have Research needs been so widely put into practice. In my view, re- Finally, I would just like to present a‘bullet’ list of the search on the nursery and grow-out phases, major topics where I believe further research and although such experiments are less easily repli- development would signi¢cantly support the future cated and need to be lengthier than work with development of commercially successful and envir- larval stages, should be a major priority. In this onmentally and socio-economically sustainable aspect of research work, I include all aspects of small- and large-scale freshwater prawn farming. management, including feeding, health manage- In my view, the important topics are: ment, nutrition, water management, optimizing Careful consideration of the economic implications and maintaining biomass levels to improve pro- of every experiment. Cost considerations should be duct marketability (in other words adapting incorporated into experimental design, so that management procedures to increase the propor- results can be quanti¢ed in ¢nancial, as well as tion of marketable prawns; of course, the de¢nition purely scienti¢c terms. In this way, the really im- of what is marketable depends on the speci¢c portant research ¢ndings can more quickly be characteristics of the market that the farmers adopted in farming practice and bene¢t both farm- wish to supply) and, perhaps most important of ers and consumers. all for this genus, practical and e¡ective size Freshwater prawns remain undomesticated, management. although unconscious (and sometimes negative) Despite my apparent bias against work with the selection may have taken place in countries where larval stages, new information that should im- the parent stocks were introduced in very small prove hatchery viability (such as those mentioned numbers. Conventional selection and breeding for earlier in this review) is still being generated.

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Further work on factors a¡ecting the broodstock Acknowledgments and larval phases of freshwater prawn farming, I would like to sincerely thank Dr C. Mohanakumar- particularly on sustainable health management in an Nair, the Convenor of the International Sympo- hatcheries and the e¡ect of broodstock nutrition sium on Freshwater Prawns, for inviting me to and management on larval quality merits contin- present the keynote address (which was based on this ued attention. In particular, resolution of the review paper) at the College of Fisheries, Kerala Agri- apparently con£icting results of studies on the cultural University, Kochi, India in August 2003. subsequent performance of early versus late- Much gratitude is also due to the Vice-Chancellor of hatching prawns in grow-out seems important. the University, Dr K. V. Peter, and to the Dean of its However, I repeat my opinion that expenditure on College of Fisheries, Dr D. D. Nambudiri, for hosting these topics should not be at the expense of ne- thesymposium.Iwouldalsoliketothankthecount- glecting workonthe nurseryand grow-out phases. less people who have helped me over several decades The ideal solution would be experiments that fol- to gather material on the topic of freshwater prawn low the comparative performance of di¡erent po- culture and research for inclusion in my own publi- pulations through both hatchery and grow-out cations, where appropriate acknowledgments will be phases. Adequate research funding and long-term found. commitment of both research managers and research scientists are prerequisites for this type of experimental work. It is clear that, in many locations, there may be va- References lue in the polyculture of freshwater prawns with other crustacea and/or ¢n¢sh; further research to ACC (2003) Aquaculture certi¢cation news, April 2003. Glo- quantify bene¢ts is required. Work on the integra- bal AquacultureAdvocate 6,7. Ahmed N. (2000) Freshwater prawn farming ^ a primary in- tion of freshwater prawn farming with other forms dustry for Bangladesh. Fish Farmer 23, 40^41. of activity sharing the same resources, such as Aiken K.A., Morris D., Hanley F.C. & Manning R. (2002) crop and livestock production, would also be Aquaculture in Jamaica. Naga,WorldFish Center Quarterly valuable. 25,10^15. Socio-economic and environmental research is Ali S. & Sahu N.P. (2002) Response of Macrobrachium rosen- also essential, to ensure that freshwater prawn bergii (de Man) juveniles to ¢sh silages as substitutes for farming is responsible and sustainable, and that ¢sh meal in dry diets. Asian Fisheries Science15,59^69. consumer attitudes towards our products (both Alston D.E. & Garc|¤a-Pe¤ rez A. (2001) Freshwater prawn yield in international and domestic markets) remain in a continuous system with hybrid red tilapia after re- positive. moving female Macrobrachium rosenbergii.In:Abstracts The use of suitable harvesting, handling and pro- of Aquaculture 2001, 21^25 January 2001, Lake Buena Vista, Fl, USA. World Aquaculture Society, Baton Rouge, cessing techniques are also important to ensure LA, USA,17pp. that our products are of high quality. In this area, Anger K. (2001) The Biology of Decapod Crustacean Larvae. I think that further studies on the e¡ect of various A.A. Balkema, Rotterdam, the Netherlands, 420pp. methods of handling prawns on product quality Anonymous (1999^2000) Nutrition of new aquaculture spe- are vitally important. The critical period between cies and crustaceans. University of Stirling Annual Report removing prawns from the rearing enclosure and 1999^2000, Institute of Aquaculture, Stirling, UK,13pp. commencing their transfer to the sites where fresh Anonymous (2000) Sustainable fresh water farming using or chilled products are marketed, or to processing farm aquafeeds. Naga,The ICLARM Quarterly 23,44. plants, merits particular attention. Anonymous (2000^2001) Systems group aquaculture pro- Finally, I would like to stress again that considera- duction systems. University of Stirling Annual Report tion of cost factors need to be a facet of all ex- 2000^2001, Institute of Aquaculture, Stirling, UK,13pp. Anonymous (2001a) Farm-made aquafeed unit launched. perimental protocols. Research results may be INFOFISH International 2,38. biologically interesting but economically impossi- Anonymous (2001b) Giant prawn farmed in Russia. INFO- ble to apply.Please think carefully about this when FISH International 2,40. designing and reporting your experimental work. Anonymous (2001c) Push for freshwater prawn farming in Those of us who are involved in peer review India. Asian Aquaculture Magazine May/June,39. for aquaculture journals should also bear this Anonymous (2001d) Thai freshwater shrimp ¢nds a future in mind. in Hainan. Asian Aquaculture Magazine July/August,14.

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Anonymous (2001e) CPF launches new breed of freshwater (ed. by B. Basurco & M. Saroglia), pp. 180^181. European shrimp. Asian Aquaculture Magazine September/Octo- Aquaculture Society,Oostende, Belgium. ber,7. ChengW.,LiuC.-H.,ChengC.-H.&ChenJ.-C.(2003)Osmol- Anonymous (2001f) CPF’s meatier strain of Macrobrachium ality and ion balance in giant river prawn Macrobrachium rosenbergii. Asian Aquaculture Magazine September/Oc- rosenbergii subjected to changes in salinity: role of sex. tober,10^11. Aquaculture Research 34,555^560. Anonymous (2001g) Filipino success on rosenbergii. Fish Correia E.S., Suwannatous S. & New M.B. (2000) Flow- Farming International 28,2. through hatchery systems and management. In: Fresh- Anonymous (2001h) City farming in the Philippines? Fish water Prawn Culture (ed. by M.B. New & W.C. Valenti), pp. Farming International 28,44. 52^68. Blackwell Science, Oxford, UK. Anonymous (2001i) Culture species in Malaysia. Asian Correia E.S., Pereira J.A., Silva A.P., Horowitz A. & Horowitz Aquaculture Magazine November/December,24. S. (2003) Growout of freshwater prawn Macrobrachium Anonymous (2002a) Paci¢c island nations set aquaculture rosenbergii in fertilized ponds with reduced levels of for- development priorities. AquacultureAsiaVII,3. mulated feed. Journal of theWorld Aquaculture Society 34, Anonymous (2002b) Consultation meeting in India on 184^ 191. shrimp genetics. Naga,The ICLARM Quarterly 25, 37. Coyle S. & Tidwell J.H. (2002) Research examines feeding re- Anonymous (2002c) Progress in the hybridisation of giant gimes for freshwater prawns. Global AquacultureAdvocate freshwater prawn. Asian Aquaculture Magazine May/ 5, 28^29. June,40. Coyle S. & Tidwell J. (2003) E¡ect of di¡erent feeds and feed- Anonymous (2002d) Indian river prawn successfully bred ing technologies on prawn production.World Aqua culture inWuxi. Asian Aquaculture Magazine July/August,7. 34,51^53. 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(2001) Improved performance of domes- D’Abramo L.R., Daniels W.H., Gerard P.D., Jun W.H. & Sum- ticated giant prawn Macrobrachium rosenbergii in Viet- merlin C.G. (2000) In£uence of water volume, surface nam. In: Abstracts of Aquaculture 2001, 21^25 January area, and water replacement rate on weight gain of juve- 2001, Lake Buena Vista, FL, USA. World Aquaculture So- nile freshwater prawns, Macrobrachium rosenbergii. Aqua- ciety,Baton Rouge, LA, USA, 45pp. culture182,161^171. BrownJ.H. (2001)Israeli Macrobrachium expert is ¢rst ‘Large Dimmock A.,Williamson I. & Mather P.(2002) Environmen- Scale Facility’visitor to Institute. Aquaculture News 27,25. tal e¡ects on morphology of mature male Macrobrachium Brown J.H. (2002) New additions in the tropical prawn unit. australiense.In:SeafarmingToday and Tomorrow. European Aquaculture News 28,24. Aquaculture Society Special Publication No.32 (ed. by B. Ba- Brown J.H., McCauley S., Ross B.,Taylor A. & Huntingford F. surco & M. Saroglia), pp.208^209. European Aquaculture (2003) A test of two methods for marking larvae and post- Society,Oostende, Belgium. larvae of the freshwater prawn, Macrobrachium rosenber- Dos Santos M.J.M. & Valenti W.C. (2002) Production of Nile gii. Aquaculture Research 34,49^54. tilapia Oreochromis niloticus and freshwater prawn Macro- Buranakanonda A. (2001) Proconco ¢nds opportunities in brachium rosenbergii stocked at di¡erent densities in poly- the Mekong Delta. Asian Aquaculture Magazine July/Au- culture systems in Brazil. Journal of theWorld Aquaculture gust, 28^29. Society 33,369^376. Buranakanonda A. (2002) Kasetsart University to improve FAO (2003) Fishstat Plus (v. 2.30), Issued 15.03.2003.FIDI, giant freshwater prawn brood stock. Asian Aquaculture Fisheries Department, FAO, Rome, Italy. Magazine May/June,15^16. Fegan D. (2002) Is vannamei fever sustainable in Asia? Global Cavalli R.O., Lavens P. & Sorgeloos P. 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chromis niloticus in polyculture and monoculture systems P. penicillatus, Metapenaeus ensis and Macrobrachium ro- in Puerto Rico. Journal of theWorld Mariculture Society 31, senbergii to benzalkonium chloride, benzethorium. Coast- 446^451. al Fisheries Series (Taiwan) 24,95^99. GonzaŁ lez-Pena M.C., Gomes S.Z. & Moreira G.S. (2002) Ef- Lutz C.G. (2003) Genetic improvement in freshwater prawns. fects of dietary ¢ber on growth and gastric emptying time Aquaculture Magazine 29,38^41. of the freshwater prawn Macrobrachium rosenbergii (De Marques de A., Lombardi J.V. & Boock M.V. (2000) Stocking Man, 1879). Journal of the World Aquaculture Society 33, densities for nursery phase culture of the freshwater 441^447. prawn Macrobrachium rosenbergii in cages. Aquaculture Goswami M. & Prasad K.P.(2000) E⁄cacy of benzalkonium 187,127^132. chloride as an antibacterial and immunostimulant in Mendoza R., MontemayorJ., Aguilera C.,Verde J. & Rodr|¤guez Macrobrachium rosenbergii (de Man). 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