[Appendix M8]

APPENDIX M
RESEARCH PROPOSALS (Cont.)

Code: Q-01
SURVEY OF MAJOR SHRIMP DISEASES AND PARASITES

1 PROPOSAL CONTENT AND EVALUATION CRITERIA

Importance and Significance of the Work

Introduction

This proposal is one of eight research plans comprising the initial research programme of the Brackishwater Station (BS) of the Fisheries Research Institute (FRI). These proposals have been prepared within the overall framework of the original Five Year Research Plan envisaged for the BS, but additionally take into account the present lack of experimental and laboratory facilities due to the delay in acquiring the selected site in Paikgacha. The proposed work should be conducted in the field using existing FRI staff who have already been assigned to the BS plus additional staff specifically recruited for the BS.

Since some access to laboratory facilities will be necessary, it is recommended that, until such time that construction of the BS is completed and it becomes fully operational, project staff will be based at the FRI headquarters at Mymensingh under the supervision of the CSO appointed for the BS.

The proposed three year study of the major diseases and parasites affecting brackishwater and freshwater shrimp in relation to water quality management in ponds should commence as soon as the necessary project staff are available.

Overview

Fisheries production in Bangladesh is extremely important to the economy. Although the capture and culture fisheries contribute about 2.9 % of the GDP and 9 % of foreign exchange earnings, fisheries products account for 6 % of the total per capita protein intake and about 80 % of the per capita animal protein intake. The estimated total fisheries production in Bangladesh during 1983–84 was 751,000 t. The production from inland waters was about 577,000 t (77 %), of which 118,400 (21 %) was contributed by aquaculture. In recent years fisheries production has declined from about 822,000 t in 1974– 75, whilst daily per capita fish consumption has fallen from 33 g in 1963–64 to 21 g in 1983–84 (a decrease of 36 %).

Even if per capita fish consumption is to be maintained at the current level, fisheries production will need to be increased to 1,100,000 t by the year 2005 in order to keep pace with the projected population growth. If daily per capita fish consumption is to reach 38 g (recommended by the Institute of Nutrition and Food Science) then production will have to be increased to 1,900,000 t. This represents an increase of about 150 % above present fisheries production levels. The Government of Bangladesh has therefore introduced an ambitious fisheries development programme in the Third Five Year Plan, to increase production from both inland and saline waters for both domestic consumption and for export (Rahman, 1986; Anon, 1985d).

The Brackishwater Station (BS) is being established by the Fisheries Research Institute to conduct research into the cultivation of brackishwater species to help meet both domestic and export requirements (Anon, 1986e, 1986g, 1987a, 1987b, 1987c; Karim, 1986a; Farmer, 1988; Muir, 1989). At the present time brackishwater aquaculture is virtually limited to shrimps of the genera Macrobrachium and Penaeus. Penaeid shrimps (mostly Penaeus monodon) currently provide an increasing source of foreign currency through exports to the USA, Europe and particularly Japan.

Brackishwater aquaculture production for local consumption is minimal. Smaller, commercially less important penaeid shrimps (Metapenaeus brevicornis and Metapenaeus monoceros) and some Macrobrachium rosenbergii are consumed locally. Small quantities of mullet (Mugil spp) are also produced as a by-product or secondary crop in some shrimp ponds.

Shrimp culture in Bangladesh started to develop in the early 1970s. At that time there was little local demand and the price of shrimp was consequently very low. The potential of farmed shrimp as a hard currency earner was quickly realised by the private sector, and within 10 years more than 26,000 ha of shrimp ponds were under cultivation. During this period the shrimp farming industry received little or no support from the Bangladesh Government. Only since 1980 with the introduction of the Second Five Year Plan (1980–85) has brackishwater aquaculture been given official recognition by the Government.

The Directorate of Fisheries has estimated that by the beginning of 1986 more than 115,000 ha had been turned over to shrimp farming activities in the whole of Bangladesh. Shrimp farming takes place in the districts of Satkhira, Khulna, Bagerhat, Barisal, Patuakhali, Bhola, Chittagong and Cox's Bazar. The two most important areas lie in the Khulna-Satkhira area to the north of the Sundarbans (ca 90,000 ha) and in the vicinity of Cox's Bazar (ca 24,000 ha). According to the Third Five Year Plan (1985–90) shrimp production is expected to increase from 9,000 t in 1984–85 to 34,000 t by 1989–90.

Market Demand and Economic importance

The local demand for fish is likely to approach 1.9 million t yr^-1 by the year 2005. Some of this demand will have to be met by increasing the production from existing inland waters through the introduction of improved husbandry and water management practices, however, other sources of fish will need to be sought. Bangladesh has about 2,500,000 ha of coastal tidal lands, of which about 2,167,000 ha may be suitable for aquaculture. There is therefore an enormous potential for increasing fish production through brackishwater aquaculture. So far these coastal tidal lands contribute very little to the domestic consumption of fish, although they are already an important and increasing source of foreign exchange through farmed shrimp exports.

The local demand for farmed shrimp in Bangladesh is poor since very few Bangladeshis eat shellfish. However, the international market is extremely important and a major source of hard currency for Bangladesh. It has been projected that the export value of shrimp will have increased from about US$ 57 million in 1984–85 to around US$ 225 million in 1989–90. Most of the shrimp produced in Bangladesh is exported to Japan. Recent export prices for shrimp shipped to Japan are shown in Table 1.

Less emphasis has been placed on the freshwater shrimp market by shrimp processing and exporting companies. This may be a reflection of the preference for marine shrimp in Japan, which is currently the main market for Bangladeshi shrimps. There are increasing market opportunities for both freshwater and brackishwater shrimp in Europe, whilst the US market can still absorb additional imports of good quality brackishwater species (Rackowe et al, 1983).

Table 1. Shrimp export prices (C&F Tokyo) January 1989.

Most shrimp farms in Bangladesh are operated on a very extensive basis, relying on natural productivity and little or no management. Current production levels generally lie within the range of <50 kg ha ^-1 yr^-1 to > 300 kg ha^-1 yr^-1, although the majority of shrimp farms are operating towards the lower end of the scale. A few enterprising farmers are claiming production levels of 900 kg ha^-1 yr^-1 or more.

In the long term there is enormous potential to increase the total production of shrimp in Bangladesh. This can be achieved in two ways: first by encouraging the introduction of more intensive shrimp farming methods whereby average production could be increased to >600 kg ha^-1 yr^-1 (Table 2), and secondly by developing freshwater shrimp farming which has the potential of being even more important economically than brackishwater shrimp farming.

Much of the area currently used for brackishwater shrimp production in the vicinity of Khulna and Satkhira, could be utilised for the production of both brackishwater shrimp during the dry season and freshwater shrimp during the rainy season. The latest estimate (1986) of the area under shrimp production is 115,000 ha. This leaves an enormous potential for increasing not only brackishwater and freshwater shrimp for export, but also brackishwater fish for local consumption.

It is, however, essential that the importance of the Sundarbans to both the capture and culture fiseries is fully appreciated and that these forests should not be cleared for the construction of fish and shrimp ponds. This issue is the subject of another closely related research proposal that has been prepared for the BS:

• Impact of Aquaculture on the Mangrove Environment: code no O-04.

Table 2. Characteristics of different levels of intensification of brackishwater shrimp farming. [In practice, the distinction between categories is artificial. A continuum exists between the lowest and highest levels of production.]

* Approximate construction cost for a bare site.

Literature Review

Overview and description

Brackishwater aquaculture has become increasingly important throughout the tropics and sub-tropics, especially in the cultivation of penaeid shrimp for export to Japan, North America and Europe. Both brackishwater and freshwater shrimp farming are still major growth industries in many parts of Asia, Africa and Latin America (Rackowe et al, 1983) and represents an extremely valuable element in the economy of many developing countries as a major source of foreign exchange.

Shrimp culture activities have traditionally been dependent on sources of wild or natural fry collected from coastal nursery areas in the case of brackishwater (penaeid) shrimp or river systems in the case of freshwater shrimp (Macrobrachium), although there has been an increasing dependence in some countries on hatchery reared fry. Brackishwater shrimp and freshwater shrimp display quite different life cycles, which need to be taken into account when considering the exploitation or even the assessment of these resources.

Penaeid shrimps are found thoughout the tropics and sub-tropics in coastal and estuarine waters. The life cycle of most penaeid shrimps follows the same general pattern. The adults spawn offshore and each female can produce up to 500,000 eggs. The minute eggs hatch very quickly after being released directly into the water. The planktonic larvae pass through a number of distinct stages (up to six naulius stages, three protozoea stages and three mysis stages) before metamorphosis. The late larval stages and postlarvae migrate towards the coast seeking lower salinity conditions in estuarine and mangrove areas before settling on the bottom. The postlarvae grow rapidly as a result of the enormous biological productivity in these coastal ecosystems.

After spending one to two months living in these rich nursery grounds the young shrimps gradually migrate away from the coast where they eventually mzature and spawn to complete the life cycle. Widespread destruction of coastal mangroves throughout the tropics and sub-tropics has led to substantial decreases in the landings of shrimp fisheries in affected areas, and shortages of shrimp fry for stocking shrimp farms.

Freshwater shrimps (Macrobrachium spp) are found throughout the tropics and sub-tropics in most inland freshwater areas including lakes, rivers, swamps, irrigation ditches, canals and ponds, as well as in estuarine areas. Most species require brackishwater during the initial stages of their life cycle, although a few species are able to complete their life cycle in inland saline and freshwater lakes. Some species prefer clear riverine conditions, whilst others (including Macrobrachium rosenbergii) are found in extremely turbid conditions.

Most Macrobrachium spp display a reversal of the migration pattern common to most penaeid shrimp. As the adult shrimps reach sexual maturity they migrate downstream into more saline conditions (≤12 ‰). As is the case amongst all the Palaemonidae the eggs are carried on the pleopods. Unlike penaeid shrimps, Macrobrachium spp normally produce only 5,000–100,000 eggs. The eggs hatch under brackishwater conditions and the larvae take several weeks to pass through 8–11 distinct larval stages before completing their metamorphosis.

The postlarvae begin to migrate upstream into freshwater conditions one to two weeks after metamorphosis and are soon able to swim and crawl against rapidly flowing currents. They are able to climb vertical surfaces and cross land provided that there is abundant moisture available (New & Singholka, 1985).

One of the major contraints to the production of increased yields of both freshwater and brackishwater shrimps in Bangladesh is the introduction of improved husbandry and, pond and water quality management practices. In spite of the importance of shrimp exports to the economy, it is surprising that so little attention has as yet been paid to this subject. There are no authoritative accounts of the limnology and water quality of shrimp ponds in Bangladesh.

Water quality management of shrimp ponds is vitally important for two basic but related reasons. First it provides the means and the opportunity for farmers to maintain optimum environmental conditions within their ponds, so that the growth and survival of shrimp can be maximised (Spotte, 1979). Secondly, the maintenance of good water quality will eliminate most of the disease and disease-related problems which are likely to be encountered by shrimp farmers (Wedemeyer et al, 1976; Tareen & Farmer, 1983). Sound pond design can also make an important contribution to the control of diseases and disease-related problems (Cruz, 1983).

Probably the two most important water quality parameters which need to be taken into account are the levels of dissolved oxygen and ammonia, however all water quality criteria are at least potentially dangerous when they approach or exceed the critical tolerance limits for a particular species being farmed. Most disease organisms only become a problem when optimum environmental conditions are not maintained.

The proliferation of disease organisms is usually the result of two main causes. In a some cases, a particular pathogen may require a very specific combination of environmental conditions for successful invasion of the host. More often, however, poor water quality induces physiological stress in the species being cultured with the result that its natural immunity and defence mechanisms become impaired.

A number of general texts for the identification and treatment of shrimp diseases are available (Johnson, 1975, 1977; Lightner, 1985; Overstreet, 1973; Sindermann, 1977; Sindermann & Lightner, 1988; Snieszco, 1970; Sprague & Couch, 1971; Tareen & Farmer, 1983). An extremely useful aid for the recognition of diseased tissues in shrimp has been written by Bell and Lightner (1988). This handbook illustrates the normal histological condition of all the major tissues of penaeid shrimp which can be used as a basis for comparison with tissues suspected of being infected.

Shrimp diseases and related phenomena can be grouped into a number of categories based on the causative agent:

Viruses:

A number of different viruses have been isolated from penaeid shrimps, only some of which result in clinical symptoms (eg Couch et al, 1975; Brock et al, 1983)

Bacteria:

Bacterial infections of shrimp have been known for many years, and most of those affecting the body fluids and tissues appear to be caused by Vibrio spp and Pseudomonas spp (eg Chan & Lawrence, 1974; Lightner & Lewis, 1975). Chitinoclastic bacteria can cause erosion of the exoskeleton (eg Cook & Lofton, 1973), whilst filamentous species can infest the gills and pleopods (eg Lightner & Supplee, 1976).

Fungi:

A number of fungi have been identified as important shrimp pathogens, including Lagenidium sp, Haliphthoros sp and Fusarium sp (eg Bian & Egusa, 1981; Lightner & Fontaine, 1973; Fisher et al, 1975). These genera invade the soft tissues of the shrimp with their hyphae and are now thought to be perhaps the most important shrimp pathogens in terms of the losses they cause in shrimp farms.

Protozoans:

Microsporidians and gregartines are common parsites and commensals in many shrimp species, but are usually harmless unless they are present in massive numbers (eg Feigenbaum, 1975; Couch, 1978; Kruse, 1959).

Ectocommensal protozoans such as Zoothamnium sp and Lagenophrys sp can cause serious problems by colonising the surface of the exoskelton to such an extent that gill function is impaired and suffocation results (eg Johnson, 1974; Lightner, 1975).

Helminths:

Various species of nematodes, trematodes and cestodes have all been identified from shrimp, which usually act as one of the intermediate hosts in the life cycle of the parasite (eg Aldrich, 1965; Margolis & Butler, 1954; Overstreet, 1973). Nematodes can kill shrimp, although trematodes and cestodes usually have no significant effect on adults.

Crustaceans:

Epicaridean crustaceans (Isopoda) can sometimes invade the branchial chambers of penaeid shrimp (eg Tareen & Farmer, 1983; Chopra, 1930). The parasite causes physiological castration of the host and often increased growth. The condition is usually rare in shrimp ponds.

Nutritional Deficiencies:

Ascorbic acid deficiency results in the syndrome known as black death (Magarelli et al, 1979). This is unlikely to be encountered in Bangladesh as it is usually associated with highly intensive systems where the shrimp are fed on complete diets (ie no other food is available).

Environmentally Induced Syndromes:

Gas bubble disease can be caused by super saturation of oxygen and nitrogen (Lightner et al, 1974). Blisters, cramped tail in larvae, and spontaneous muscle necrosis appear to be caused by oxygen starvation and other environmental problems (eg Delves-Broughton & Poupard, 1976; Johnson, 1975; Fontaine & Lighner, 1974; Tareen, 1980).

Epiphytes:

In exceptional circumstances epiphytic filamentous algae of the genus Entaromorpha can colonise the exoskeleton of shrimp (eg Tareen & Farmer, 1983). This condition appears to be associated with very high dissolved nitrogen levels (NO₃- & NO₂-) in intensive culture systems.

Pesticides:

All pesticides that have been developed for controlling insects are potentially very dangerous to crustaceans and shrimp in particular. Pesticides resulting from arial spraying or runoff from agricultural crops can cause hyperactivity, tremors, paralysis followed by death in the case of acute poisoning. In cases of chronic poisoning death is usually preceded by lethargy (eg Couch, 1978).

Heavy Metals:

Heavy metals are unlikely to be a serious problem in Bangladesh since there are virtually no chemical industries operating in the shrimp farming areas. Mercury, cadmium are amongst the most toxic to shrimp although high concentrations of most heavy metals in soluble form are likely to be problematic (eg Sparks, 1985).

A major constraint to the future growth of both freshwater and brackishwater shrimp farming in Bangladesh is likely to be the current lack of awareness and expertise in basic animal husbandry and water quality management. The basic cause of most disease-related problems in aquaculture is very often the failure to maintain adequate water quality. Insufficient attention is currently being paid to the basic needs of the shrimp, especially in terms of pond and water quality management. As yet no studies have been carried out in Bangladesh on the occurrence of shrimp diseases and parasites in relation to water quality.

Current Status of Shrimp Culture in Bangladesh

As has already been described, there is currently very little brackishwater aquaculture in Bangladesh in relation to the potential for future development. Virtually all brackishwater production at the present time is directed towards the farming of brackishwater penaeid shrimp for export.

Most shrimp farming has developed within polders created by the Bangladesh Water Development Board (BWDB) in low-lying coastal flood plains. These activities have been started without the consent of the BWDB, and one of the major concerns has been the creation of unauthorised sluice gates or channels through the perimeter dykes of the polders. Only those areas that are low enough to permit inundation of the land by at least 0.5 m of water at spring tides have generally been used for shrimp farming.

Only two species are deliberately stocked in ponds: Penaeus monodon and Macrobrachium rosenbergii. Of these P monodon is by far the more important. Other species of penaeid shrimps are also cultivated, through the accidental introduction of their fry when the ponds are filled or water exchange takes place. These include: Penaeus indicus, Penaeus merguiensis, Metapenaeus monoceros and Metapenaeus brevicornis.

Shrimp farming in Bangladesh relies entirely on the supply of wild fry for stocking purposes. It has been estimated that 1–3 billion fry of P monodon were harvested in 1985. The main collection centres are Satkhira, Khulna, Bagerhat and Cox's Bazar. At present, most fry collection for P monodon is conducted within the rivers and creeks of the coastal flood plain. It has been suggested that there may be a huge unexploited resource within the Sundarbans.

Collection of shrimp fry is carried out using either a fixed bagnet (behundi jal) which relies on tidal streams in small rivers and creeks to carry postlarval shrimp into the codend, or alternatively triangular (or less frequently rectangular) nets which are pushed or pulled along the bed of the river or creek. In Cox's Bazar shrimp fry collection is also carried along the beach. In the Khulna-Satkhira area the peak season for shrimp fry is February-May, whilst at Cox's Bazar it is April-June.

Shrimp fry collectors transfer their catches to earthenware bowls which are then carried back to the villages where the fry are sorted and counted by children using white enamelled plates. This undoubtedly results in a very large wastage of fry of both penaeid shrimps and other commercially important species including fish. The shrimp fry then pass through a chain of middlemen before reaching the shrimp farmers, during which the fry are usually transported in 20–30 l aluminium vessels using every conceivable form of transport. Shrimp fry mortality is believed to be very high, due to extreme water temperature and salinity fluctuations, low dissolved oxygen levels, and even the use of table salt in the mistaken belief that this will provide the correct salinity for the fry.

The price of P monodon fry in the Khulna-Satkhira area has risen dramatically from about Tk 40–50 in 1980 to Tk 400–600 per thousand (postlarvae of ca 15 mm total length) in 1988. The price of shrimp fry is much lower in the vicinity of Cox's Bazar being only Tk 40–100 per thousand for fry of a similar size.

Macrobrachium fry (postlarvae and juveniles) are collected in the Khulna region for stocking freshwater or low salinity brackishwater shrimp farms. There are no estimates available on the number of fry collected annually. Fry are available in the Khulna area from April onwards with the peak demand occurring in July. The price of Macrobrachium fry in the Satkhira area in 1986 was Tk 500–1,000 per thousand (25–50 mm total length), although at Paikgacha prices were only half this figure. Hatchery reared Macrobrachium fry produced in Cox's Bazar were being sold in 1988 for Tk 440 per thousand (15–20 mm total length).

In the Khulna-Satkhira area the shrimp farming pattern, often in rotation with agriculture, reflects the ambient seasonal salinity fluctuations in response to the monsoon:

January-July [high salinity season]:

• Culture of brackishwater shrimp and fish.
• Harvesting of marketable individuals.

August-December [low salinity season]:

• Continued culture of under-sized shrimp and fish in low-lying areas subject to the salinity tolerance of the species.
• Culture of freshwater shrimp and fish.
• Cultivation of slightly salt-resistant aman rice in more elevated areas.
• Harvest of residual brackishwater shrimp and freshwater shrimp.

In the Cox's Bazar area this pattern may be reversed due to the generally higher ambient salinities. Therefore some farmers produce salt during the the dry season and brackishwater shrimp during the rainy season.

Most of the shrimp farming is carried out within larged dyked areas (polders or ghers). Transplanted aman rice can be grown from August-December, when water and soil salinities are low. Agricultural crop production from January to July is difficult due to the shortage of freshwater and increased salinities in the soil. Acid sulphate soils may also present special problems in some areas.

Before the recent and rapid growth of shrimp farming, the land used to be left fallow during the dry season and used instead for grazing cattle and water buffalo. Animal dung remaining on the land, if not collected for fuel, would help to increase the production of aman rice in the following rainy season. The loss of grazing has resulted in very serious conflicts in land use in some areas.

Until recently all shrimp farmers, either individually or in groups, have leased land within BWDB polders. In some cases the land has been seized from the rightful leaseholders by force. The BWDB perimeter dykes are deliberately breached and wooden sluice gates or reinforced concrete culverts installed before repairing the dykes. The ponds, which may extend up to 500 acres (200 ha) or more, are usually allowed to remain dry during January after havesting the rice. The stubble is left in place. The ponds are then flooded during spring tides.

Since the early 1980s the Government of Bangladesh has played an active rôle in improving the level of shrimp farming husbandry and technology. Screens to prevent the entry of predators and competitors have become much more widespread, in combination with the selective stocking of fry. Simple nursery production methods have been introduced in some cases through the construction of a shallow nursery pond within the confines of each growout pond. Pond preparation, liming, fertilisation, pest control, nursery production, supplementary feeding and water management have only started to be introduced during the last five years, and even now are employed in only a few areas.

Recently P monodon production has been increased by the more enterprising farmers from <50 kg ha^-1 yr^-1 to >300 kg ha^-1 yr^-1. In the case of the Allah-Wala shrimp farm at Cox's Bazar, production of up to 900 kg ha^-1 yr^-1 was claimed during 1988.

There are plenty of signs that shrimp production levels in Bangladesh will continue to rise as a result of the gradual introduction of more intensive practices. At the present time, however, most farms are operated on an extensive basis, with relatively few examples of semi-intensive production.

Although there is an enormous potential for the development of both freshwater and brackishwater shrimp farming in Bangladesh, there is relatively little scientific literature available in respect of the shrimp resources of Bangladesh. It is therefore very important that basic scientific data on the both freshwater and brackishwater shrimp should be obtained in order to exploit the full potential of these resources in Bangladesh.

Previous Research in Bangladesh

Some research on the development of brackishwater shrimp cultivation has already been completed at Chittagong University (sponsored by BARC) and the Directorate of Fisheries.

Chittagong University:

• Culture of plankton for feeding fish and prawn larvae to be used in mariculture (1977–1982). [BARC.]
• Biology and production of prawn, Penaeus monodon (1977–1982). [BARC.]
• Development of technology of production of seeds of golda chingri, Macrobrachium rosenbergii (1977–1982). [BARC.]

Directorate of Fisheries:

• Shrimp culture demonstration project at Satkhira: demonstration of improved culture techniques; provision of practical training for fishery officers, identification of the socio-economic support required to assist small scale shrimp farmers. [FAO/BOBP.]

The first of the public sector shrimp farming activities in Bangladesh was the Bay of Bengal Programme (BOBP) shrimp farm at Satkhira. This semi-intensive demonstration and research unit has recently been taken over by the Gramin Bank and is now known as the Satkhira Shrimp Farm.

Very little by way of practical research results is available from these various projects.

Present Status of Research in Bangladesh

Research on shrimp culture is currently being undertaken or alternatively being planned by the Fisheries Research Institute, the Directorate of Fisheries and Chittagong University. In most cases this work has only started recently and few research results are available. Some of this work is sponsored by BARC, whilst the rest is supported by ADB, FAO/UNDP and the World Bank. The various projects are summarised below:

Fisheries Research Institute:

• Establishment of the Brackishwater Station (formerly designated the Brackishwater Fisheries Research Station) at Paikgacha. Part of the World Bank Second Agricultural Research Project. [WB/FAO/UNDP.]

Directorate of Fisheries:

• Marine fisheries research, management and development. Physico-chemical and biological studies of the estuarine environment in the Cox's Bazar region and coastal aquaculture experiments. [JICA/FAO/UNDP.]
• Aquaculture development project: establishment of a penaeid hatchery at Cox's Bazar; setting up a shrimp culture estate in the Chakaria Sundarbans, and establishment of a hatchery at Cox's Bazar. [ADB.]
• Expansion of shrimp/fish culture in coastal districts: establishment of two experimental pond complexes (Khepupara and Charfesson) and provision of extension services in improved culture techniques. [In house.]
• IDA Shrimp Culture Project: upgrading of 5,600 ha of existing shrimp farms in the Cox's Bazar and 1,400 ha in the Khulna districts; provision of operational funds to the farmers of the above upgraded farms; provision of credit for an additional 2,500 ha of existing farms not upgraded through the Project's direct efforts; demonstration and extension of improved culture techniques; provision of training for fishery officers and farmers. [IDA/FAO/UNDP.]

Chittagong University:

• Studies on growth and quality of shrimp and mullet with supplementary feeds (1986 onwards).

The largest of the Government shrimp farming projects is the IDA Shrimp Culture Project which is being adminstered by the Directorate of Fisheries. The Project comprises two parts: one near Khulna and another south of Cox's Bazar. The budget for the entire project is 117 crore Taka (US$ 36.5 million). The six year Project (1985/86 to 1990/91) involves the development of 3,500 acres (1,405 ha) of shrimp-cum-paddy farming in the Khulna area, most of which will be leased to individual farmers as 10 acre (4 ha) ponds. This part of the Project will also operate a demonstration farm and a hatchery, and provide an extension service for the leaseholders and other local farmers.

The second part of the IDA Shrimp Culture Project based at Cox's Bazar will comprise a penaeid shrimp hatchery and 5,000 acres (2,000 ha) of shrimp ponds at Rampura within an existing polder with a perimeter of 39 miles (62 km). Single 10 acre (4 ha) ponds will be leased to individual shrimp farmers. A further 12,000 acres (4,900 ha) have been earmarked for subsequent development by the private sector. In the long term it is planned to establish a total of nine private hatcheries. A 22 acre (9 ha) demonstration farm and training centre will be built soon on a site already selected at Teknaf.

The ADB shrimp farming project at Rampura, also near Cox's Bazar, comprises a 50 acre (20 ha) demonstration shrimp farm for penaeid shrimps and a further 1,715 acres (700 ha) for private farmers. The concept is the same as for the IDA project in that single 11 acre (4 ha) ponds will be leased to 115 individual shrimp farmers. The demonstration farm comprises 13 growout ponds of 13.4 ha each and four smaller nursery ponds.

As soon as the Brackishwater Station of the Fisheries Research Institute has been constructed and becomes fully operational, the FRI will play an increasingly important national rôle in the development of the shrimp farming industry in Bangladesh.

2 PURPOSE AND OBJECTIVES

The overall purpose of this research project is to identify shrimp diseases and parasites occurring in Bangladesh and the relationship between their incidence and water quality criteria. The project will include the monitoring of selected freshwater and brackishwater shrimp ponds in the general Khulna-Satkhira area north of the Sundarbans and in the vicinity of Cox's Bazar.

Selection of Sites

Objective: To select a number of brackishwater and freshwater shrimp ponds for subsequent monitoring of disease and water quality, which represent the full range of current management practices from the most extensive to the most intensive.

Field Studies

Objective: To identify the major shrimp diseases and parasites occurring in cultured shrimp populations in response to water quality characteristics in both freshwater and brackishwater ponds.

Species Identification

Objective: To identify and list all the major diseases and parasites affecting both freshwater and brackishwater shrimp in Bangladesh.

Diagnostic Services

Objective: To provide a extension service for shrimp farmers covering the identification of diseases and parasites, and the provision of advice for their control or elimination through the introduction of improved pond and water management practices.

Report Preparation

Objective: To prepare a final report consisting of a description of the work undertaken during the course of the project, the methodology, the results and their subsequent analysis and interpretation, and the formulation of recommendations for the introduction of improved pond and water quality management practices in Bangladesh.

Project Management

Objective: To provide overall technical and administrative control of the research project, co-ordination with other projects, other sections of FRI and other Government agencies, and the preparation of concise quarterly progress reports covering both research and administrative issues.

3 WORK PLAN SUMMARY

Work Plan Summary

This project has been designed to provide basic data for the future research programme of the BS once the laboratory and experimental facilities are fully operational. The information collected by the project will provide an important data base for the future development of the shrimp farming industry in Bangladesh.

During the first four months the proposed project will be involved in the selection of a number of representative brackishwater and freshwater shrimp ponds for subsequent monitoring over three complete culture seasons. Shrimp samples for pathological examination and measurements of water quality will be taken in each shrimp pond on a weekly basis. Water temperature, salinity, dissolved oxygen concentration, nutrient levels (NO₃-, NO₂-, NH₄+, PO₄³-) and pH will be measured in order to determine the relationship, if any, between current water management practices and the incidence of diseases and parasites.

After a period of 30 months, during which three complete culture seasons will be monitored in both freshwater and brackishwater ponds in the Khulna-Satkhira and Cox's Bazar areas, the data will be analysed and interpreted in order to formulate effective pond and water management practices to eliminate or at least control disease-related problems. During the last year of the project a diagnostic service will be established to provide extension support for the shrimp farming industry in Bangladesh.

The implementation of this project will additionally provide an excellent opportunity for research and technical staff recruited for the BS to gain useful field experience in survey and research activities prior to the BS becoming fully operational. This should make the process of commissioning the BS and implementing the full research programme a much easier task for the appointed CSO. The project can also be used to provide ad hoc training for technical and support staff during its three years' duration.

Task Scheduling

The scheduling of the major project activities or tasks is summarised in Table 3. Ideally the project should be timed to conincide with the shrimp production seasons at Cox's Bazar and in the Khulna-Satkhira area. The approximate seasons are as follows:

Khulna-Satkhira Area:

• Brackishwater season - January to July
• Freshwater season - August to December

Cox's Bazar Area:

• Fully saline season - January to July
• Brackishwater season - August to December.

Table 3. Activity chart (time scale: units of 2 months).

- Project activity/task.
* Reporting date.
# Extension service to shrimp farmers.
^x Experiments on disease/water quality relationships.

4 METHODOLOGY AND PROCEDURES

The methodology and procedures to be utilised in this project have been kept as simple as possible in order to permit the completion of the project without the need for the specialised facilities which will eventually becaome available at the BS. There will, however, be some need for laboratory work and it is proposed that this should be undertaken primarily at the FRI Freshwater Station's laboratories at Mymensingh. Since some of the field work will be undertaken in the Cox's Bazar area, it is recommended that the FRI Marine Station at Cox's Bazar should be utilised for laboratory investigations of samples collected in that area.

The project will investigate the occurrence of shrimp diseases and parasites in aquaculture ponds in relation to water quality. The project will also provide a diagnostic service to shrimp farmers in the identification of disease-related problems and advice for corrective action.

Preparation of the Work Plan

At the start of the project the principal investigator should translate the project proposal into a written and detailed work plan which should be approved by the CSO of the BS before the research investigations get underway. This work plan should define the following elements: project objectives; detailed methodology; equipment and consumable requirements; logistic support requirements; areas requiring co-operation or co-ordination with other projects or sections of FRI; staff assignment and manpower requirements, and reporting deadlines. A period of one month has been allowed for the preparation of the work plan and its approval by the CSO of the BS.

Literature Review

Before commencing the field work components of the project, a thorough review of the literature should be made. The bibliography appended to this proposal not only includes references for those citations incorporated in the text, but also recommendations for background reading. The FRI Library and Documentation Centre should obtain as many as possible of these references before that start of the project. These should be reviewed and digested by the principal investigator and his scientific staff at the beginning of the project. A period of four months has been allowed for the completion of this task in view of the large volume of scientific literature which needs to be consulted.

Site Selection

A minimum of 18 ponds should be selected for routine pathology and water quality investigation during a period of 30 months. This period should be sufficient to cover three complete culture seasons if the timing of the project is scheduled correctly. The ponds should be chosen to provide the following combination:

• 6 ponds for penaeid shrimps (Cox's Bazar)
• 4 ponds for penaeid shrimps (Khulna-Satkhira)
• 8 ponds for Macrobrachium spp (Khulna-Satkhira)

At Cox's Bazar two of the ponds selected should be currently operated semi-intensively (eg Allah-Wala Ltd and Beximco), two should be operated very extensively, whilst the remaining two should fall between the other two pairs. At present there are no truly semi-intensive shrimp farming operations in the Khulna-Satkhira area. Therefore one pair of ponds should be selected at the lowest level of intensification, whilst the second pair should represent the highest level currently being practised. This arrangement should be duplicated for both freshwater and brackishwater shrimps in the Khulna-Satkhira area, except that twice as many freshwater shrimp ponds should be monitored.

It is essential that the ponds are selected carefully, since the routine sampling will require the co-operation of the shrimp farmer over an extended period. It should not be necessary to provide any incentive for the shrimp farmers since they will in effect be receiving a very personal ‘extension service’ during the field investigations. The results and conclusions of the study should of course be communicated to them both during and at the end of the research project. A period of four months has been allowed for the pond selection and for making all the necessary arrangements with the shrimp farmers concerned.

Pond Management Records

It will be necessary for the shrimp farmers co-operating in this project to keep very detailed records of their daily activities throughout the three culture seasons. It is recommended that pre-printed diaries are prepared for this purpose, so that the farmers get into the habit of recording all the relevant information on a regular basis. The minimum information required by the project will be:

• Date of first operation of farm
• Previous shrimp yields [kg ha^-1]
• Exact area and dimensions of shrimp pond
• Details of water supply
• Pond preparation (if any) before stocking
• Stocking date
• Stocking rate and, size and source of fry
• Fertiliser type and rates (if provided)
• Shrimp feed type and rates (if provided)
• Water exchange rates and times
• Unusual shrimp behaviour
• Unusual appearance of the shrimp
• Harvesting date(s)
• Shrimp production yield [kg ha^-1]

Field Studies

Samples of shrimp and the most important water quality parameters will be monitored weekly in each of the ponds throughout three complete culture seasons.

Live shrimp samples should be collected by using cast nets or traps. The shrimp should be examined immediately after capture in order to detect any obvious signs of disease or stress. The sample should then be preserved in ethanol (70 %) or formalin solution (5 %) for subsequent examination in the laboratory (see the next task: Species Identification). In addition ad hoc samples of shrimp from any farmer known to have a disease-related problem should also be collected and preserved for subsequent examination and diagnosis.

Water quality measurements or samples should be taken where possible half way between the surface and the bottom of the pond. The parameters to be measured will include:

• Water temperature
• Salinity
• Dissolved oxygen concentration
• pH
• Nitrate
• Nitrite
• Ammonia
• Phosphate
• Turbidity

Depending on the size of each pond being monitored, several measurements for each parameter at different locations may need to be taken in order ensure that representative samples of the water quality in each pond have been measured.

Water Temperature

Water temperatures should be measured weekly using a standard mercury thermometer capable of being read to 0.1 °C.

Salinity

Salinities should be measured weekly using a temperature compensated salinity refractometer capable of being read to 1.0 ‰.

Dissolved Oxygen Concentration

Dissolved oxygen concentration should be measured hourly over a period of not less than 24 hours each week using a portable oxygen meter capable of being read to 0.1 mg 1^-1. The relationship between the solubility of oxygen in water in relation to temperature and salinity is provided in section 6 ANNEXE (Table 5).

pH

pH levels should be measured weekly with a portable pH meter capable of being read to 0.1 pH unit.

Nitrogen

Nitrate, nitrite and ammonia levels should be measured weekly to the nearest 0.1 mg 1^-1 using a select ion/pH meter with separate NO₃-, NO₂- and NH₄+ electrodes, or a suitable spectrophotometer. When monitoring ammonia it is also necessary to measure the pH simultaneously in order to determine the relative dissociation of ammonium ions into free ammonia. Free ammonia is many times more toxic than ammonium ions. The dissociation relationship between ammonia and ammonium ions in response to temperature and pH is provided in section 6 ANNEXE (Table 6).

Phosphorus

Phosphorus (phosphate) levels should be measured weekly to the nearest 0.1 mg 1^-1 by titration or preferably by spectrophotometer.

Turbidity

Relative turbidity (light penetration) should be measured weekly using a Secchi disc and the depth at which the disk disappears from sight recorded to the nearest whole centimetre. This will be used as a relative indicator of the density of the phytoplankton population in the ponds.

Minimum water quality requirements for both brackishwater and freshwater tropical shrimp are provided in Table 4. In additional to those parameters which will be measured during the course of this project, others have been included in case it is decided to extend the scope of the project at a later stage. Details of analytical methods for water quality are available in Strickland and Parsens (1968) and Boyd (1979).

Species Identification

Where possible all disease organisms and parasites will be identified on the basis of their monphological characters using both low power and high power microscopes. In the first instance identification should be made utilising one or more of the general shrimp pathology texts (Johnson, 1975, 1977; Lightner, 1985; Overstreet, 1973; Sindermann, 1977; Sindermann & Lightner, 1988; Snieszce, 1970; Sprague & Couch, 1971; Tareen & Farmer, 1983). More detailed descriptions (see section 6 BIBLIOGRAPHY) can be consulted to confirm the diagnoses.

Wherever possible, any disease-related problems that are identified should be corrected through the implementation of improved water quality management practices. It is, however, recognised that in many of the extensive culture systems being used in Bangladesh this is unlikely to be feasible due to the design of the ponds and water supply.

Histological examination of tissues and the incubation of bacterial and fungal pathogens will not be possible until the BS becomes fully operational. If serious fungal or bacterial disease outbreaks occur, then the assistance of a medical or veterinary university department should be obtained until such time that the BS has the necessary facilities. If, after exhaustive examination for other causative agents, it is suspected that viruses may be the cause of a serious problem, then it is recommended that one of the the following laboratories be contacted for specialist assistance:

- Dr D J Alderman
Fish Diseases Laboratory
Ministry of Agriculture, Fisheries and Food
Weymouth
Dorset
United Kingdom

- Dr D V Lightner
Environmental Research Laboratory
University of Arizona
Tucson
Arizona 85706
USA

- Dr S K Johnson
Department of Wildlife and Fisheries
Texas A & M University
College Station
Texas 77840
USA

Table 4. Basic water quality requirements for tropical shrimp.

? Tentative value or value unknown.
* May originate from areas of high yield rice production.
# Used as pesticides in shrimp farms in some countries, although the practice should generally be discouraged.

Diagnostic Services

During the third year of the project, a diagnostic service will be offered to shrimp farmers on request. It will be necessary to advertise this service throughout the shrimp farming areas. This will include: visits to affected ponds; the collection of samples; identification, and the provision of advice for remedial action when appropriate. The benefits of this service should be evaluated towards the end of the project, and recommendations formulated for its possible continuation on a routine basis. It should determined whether this service should be provided by FRI or perhaps another Government agency (eg the Directorate of Fisheries).

Analysis and Interpretation

Statistical analysis and interpretation of the results of the field surveys should follow immediately after each season's measurements. The final period of analysis should be completed within two months and result in the formulation of pond and water quality management practices specifically for disease control for general introduction in Bangladesh. The project will also formulate recommendations for the introduction of improved pond design especially in relation to water exchange and quality.

Specialist Equipment Requirements

The following specialist equipment and supplies will be required:

• Salinity refractometers (temperature compensated) [x 4]
• Dissolved oxygen meters* [× 4]
• Select ion/pH meter with separate NO₃-, NO₂- and NH₄+ electrodes [x 2]
• Spectrophotometers [× 2]
• Water sample bottles (polypropylene) [250 ml × 100]
• Secchi disc [x 4]
• Vernier callipers [x 2]
• Low power stereoscopic microscopes [x 2]
• High power binocular microscopes [x 2]

* Supplier: Yellow Springs Instrument Company Inc. USA.

Manpower Requirements

The project will require the following manpower:

• Principal investigator (team leader) 1
• Field/laboratory technicians* 2
• Boat operator (Cox's Bazar) 1
• Driver (Khulna-Satkhira) 1

* One for each site.

Budget Estimates

The budget estimates will be prepared by BS/FRI staff at a later stage.

Project Management

The principal investigator (team leader) will be responsible for the day to day technical and administrative management of the project under the overall direction of the CSO of the BS. Until such time that the BS is fully operational, laboratory and administrative support will have to be provided by the FRI at Mymensingh. To a lesser extent laboratory support will also have to be provided by the MS at Cox's Bazar.

The assignment of individual work tasks and the timing of those tasks will be the responsibility of the principal investigator in collaboration with the CSOs of the BS and MS, and the principal investigators of other projects. Since the BS will not be operational for some time, the project will need to utilise laboratory facilities of the FS at Mymensingh. The success of the project will therefore be dependent in part on the degree of co-operation between BS, FS and MS scientific staff.

Efficient co-ordination between the CSOs of the BS, FS and MS will permit the shared use of facilities and equipment until such time that the BS becomes fully operational. Where project staff are not required on a continuous basis, they should be temporarily assigned to other projects in order to make the most effective use of their time. It may be possible to combine field sampling and other field work with related projects in order to use FRI and BS resources as efficiently as possible.

The principal investigator will be responsible for the initial planning of the field investigations, monitoring of the data collection and analysis, and in conjunction with the other members of the team, interpretation of the results and report preparation. The principal investigator should meet with his project team on a weekly basis to ensure schedules are being met and to resolve problems or other project-related issues.

Reporting

Quarterly progress reports and a final project report should be prepared by the principal investigator with assistance from the other team members. The responsibility for the quality of the quarterly and final reports and their submission on time will be the responsibility of the principal investigator alone. It must, however, be recognised that administrative support to achieve this end will need to be provided by the FRI until such time that the BS is fully operational, after which it will become the responsibility of the CSO of the BS.

The CSO of the BS will also be responsible for reviewing the progress and final reports and making sure that the individual activities of the project have been completed properly and on time. Delays and other problems affecting the success of the project should be identified as early as possible so that corrective action can be taken.

5 BIBLIOGRAPHY

[It should be noted that the bibliography contains not only those references cited in the text of this proposal, but also suggestions for additional background reading prior to the start of the project.]

Afonso, J M M, 1982. First remarks on the occurrence of Gregarina sp on the larval culture of Penaeus paulensis. Atlantica, 5 (2): 2. [Special issue: abstract only.]

Akita, G, R Nakamura, J Brock, G Miyamoto, M Fujimoto, F Oishi, D Onizuka & D Sumikawa, 1981. Epizootiologic study of mid-cycle disease of larval Macrobrachium rosenbergii. Journal of the World Mariculture Society, 12 (2): 223–230.

Aldrich, D V, 1965. Observations on the ecology and life cycle of Prcchristianella penaei Kruse (Cestoda: Trypanorhyncha). Journal of Parasitology, 51: 370–376.

Ali, M Liaquat, 1983. Shrimp farm survey in coastal area of Bangladesh, Dhaka. [Mimeographed.]

Anonymous, 1979. Draft final report, Annexe B. Proposed fisheries components for an agricultural credit project. Agricultural Credit Studies Project. Prepared by Nathan Associates, USA on behalf of the Bangladesh Bank, Dhaka.

Anonymous, 1984a. National Water Plan Project. Second interim report, vol VII - Fisheries. Master Plan organisation, Ministry of Water Development and Flood Control, Bangladesh. Prepared by Harza Engineering Co Int.

Anonymous, 1984b. Bangladesh coastal aquaculture project engineering study. Draft report, vol 1. Prepared by Development Consultancy Services Ltd and Engineering Consultancy Services Ltd, Dhaka on behalf of the World Bank.

Anonymous, 1985a. Delta Development Project: Bangladesh-Netherlands Joint Programme under the Bangladesh Water Development Board. Shrimp culture in the semi-saline zone of the delta. Technical report no 13, volume I, 60 pp. Arnhem and The Hague, The Netherlands.

Anonymous, 1985b. Delta Development Project: Bangladesh-Netherlands Joint Programme under the Bangladesh Water Development Board. Shrimp culture in the semi-saline zone of the delta. Technical report no 13, volume II, 102 pp. Arnhem and The Hague, The Netherlands.

Anonymous, 1985c. Report on tidal areas study. Draft report prepared by Development Consultancy Services Ltd and Engineering Consultancy Services & Associates Ltd, Dhaka on behalf of FAO.

Anonymous, 1985d. List of projects for the Third Five Year Plan. Planning Commission, Government of Bangladesh.

Anonymous, 1985e. Report on engineering study. Vol 1: Bangladesh coastal aquaculture project. Prepared by Development Consultancy Services Ltd and Engineering Consultancy Services Ltd, Dhaka on behalf of the World Bank.

Anonymous, 1985f. Twenty year fishery development plan for Bangladesh. Prepared by John C Marr & Associates on behalf of FAO/UNDP.

Anonymous, 1986a. Bangladesh Second Aquaculture Development Project. Preparation report. Prepared by Aquatic Farms Ltd, Hawaii, USA on behalf of the Government of Bangladesh and the Asian Development Bank.

Anonymous, 1986b. Draft feasibility report on package 1: Khulna Coastal Embankment Rehabilitation Project (TA no 665-BAN). Vol I. Prepared by Agricultural Development Corporation (ADC), Seoul, South Korea in association with Associated Consulting Engineers (Bangladesh) Ltd.

Anonymous, 1986c. Draft feasibility report on package 1: Khulna Coastal Embankment Rehabilitation Project (TA no 665-BAN). Vol III. Prepared by Agricultural Development Corporation (ADC), Seoul, South Korea in association with Associated Consulting Engineers (Bangladesh) Ltd.

Anonymous, 1986d. Socio-economic impact and constraints of shrimp farming in Bangladesh. Fisheries Research Institute - Bangladesh, project proposal no 4, 59 pp.

Anonymous, 1986e. Brackishwater Aquaculture Research Station (BARS): design - phase 1. Fisheries Research Institute - Bangladesh, FAO/UNDP TA Project BGD/83/010 report no 3, 22 pp.

Anonymous, 1986f. Research plans for nutrition and feed technology. Fisheries Research Institute - Bangladesh, FAO/UNDP TA Project BGD/83/010 report no 4, 146 pp.

Anonymous, 1986g. Research plans for the Brackishwater Fisheries Research Station (BFRS). Fisheries Research Institute - Bangladesh, FAO/UNDP TA Project BGD/83/010 report no 5, 24 pp.

Anonymous, 1987a. Fisheries Research Institute - Bangladesh. Five Year Masterplan: General research plan. FAO/UNDP TA Project BGD/83/010. Arnhem: Euroconsult BV, 149 pp.

Anonymous, 1987b. Brackishwater Fisheries Research Station (BFRS): design - phase 2. Fisheries Research Institute - Bangladesh, FAO/UNDP TA Project BGD/83/010 report no 13, 125 pp.

Anonymous, 1987c. Five Year Masterplan: Equipment and civil Works (final version). Fisheries Research Institute - Bangladesh, FAO/UNDP TA Project BGD/83/010 report no 14, 26 pp.

Anonymous, 1987d. Advice on literature. Fisheries Research Institute - Bangladesh, FAO/UNDP TA Project BGD/83/010 report no 15, 50 pp.

Anonymous, 1988a. Government of the People's Republic of Bangladesh. Fisheries Research Institute (FRI): Revised project. Mymensingh: Fisheries Research Institute, 112 pp.

Anonymous, 1988b. Project of the Government of the People's Republic of Bangladesh. Integrated resource development of the Sundarbans reserved forest. UNDP project document, BGD/84/056/A/01/12, 27 pp plus annexes.

Anonymous, 1988c. Regional overview, status of facility and coastal aquaculture research proposals. Fisheries Research Institute - Bangladesh, FAO/UNDP TA Project BGD/83/010 report no 19, pag var.

Bangladesh Bureau of Statistics, 1986. 1986 Statistical Yearbook of Bangladesh. Dhaka: Ministry of Planning, 1048 pp.

Bangladesh Bureau of Statistics, 1985. Statistical Pocket Book of Bangladesh 1984–85. Dhaka: Ministry of Planning, 654 pp.

Barkate, J A, C R Laramore, Y Hirono & H Persyn, 1974. Some marine micro-organisms related to shrimp diseases. Proceedings of the World Mariculture Society, 5: 267–282.

Baticados, M C L, R M Coloso & R C Duremdez. Studies on the chronic soft-shell syndrome in the tiger prawn, Penaeus monodon Fabricius, from brackishwater ponds. Aquaculture, 56 (3–4): 271–285.

Bell, T A & D V Lightner, 1988. A Handbook of Normal Penaeid Shrimp Histology. Aquaculture Development Program, Department of Land and Natural Resources, State of Hawaii. Baton Rouge, Louisiana: World Mariculture Society, 114 pp.

Bian, B Z & E Egusa, 1981. Histopathology of black gill disease caused by Fusarium solani (Martius) infection in the kuruma prawn, Penaeus japonicus Bate. Journal of Fish Diseases, 4: 195–201.

Bland, C E, 1974. Occurrence and distribution in North Carolina waters of Lagenidium callinectes Couch, a fungal parasite of blue crab ova. Cheasapeake Science, 15: 232–235.

Bland, C E, D G Ruch, B R Salser & D V Lightner, 1976. Chemical control of Lagenidium sp, a fungal pathogen of marine Crustacea. Proceedings of the World Mariculture Society, (7): 445–472.

Boyd, C E, 1979. Water quality in warmwater fish ponds. Auburn (Alabama, USA): Auburn University, Agricultural Experiment Station.

Brisson, S, 1985. Gas-bubble disease observed in pink shrimps, Penaeus brasiliensis and Penaeus paulensis. Aquaculture, 47 (1): 97–99.

Brock, J A, D V Lightner & T A Bell, 1983. A review of four virus (BP, MBV, BMN and IHHNV) diseases of penaeid shrimp with particular reference to clinical significance, diagnosis and control in shrimp aquaculture. Meeting of the International Council for the Exploration of the Seas, 1983, Copenhagen, Denmark. ICES report no CM-1983/Gen: 10, 20 pp.

Burns, C D, M E Berrigan & G E Henderson, 1979. Fusarium sp infections in the freshwater prawn Macrobrachium rosenbergii (de Man). Aquaculture, 16 (3): 193–198.

Camacho, L, 1987. Epizoic ciliates from pond-reared adult prawns of Macrobrachium rosenbergii. 40th Annual Meeting of the Society of Protozoologists: Program and Abstracts. Chicago: Society of Protozoologists, p 22. [Abstract only.]

Chan, E S & A W Lawrence, 1974. The effect of antibiotics on the respiration of brown shrimp larvae to postlarvae and bacterial populations associated with shrimp. Proceedings of the World Mariculture Society, 5: 99–124.

Chopra, B, 1930. Further notes on bopyrid isopods parasitic on Indian Decapoda Macrura. Records of the Indian Museum, 32: 113–147.

Chowdhury, A Q, 1986. Fishermen community and development of closed water fishery in Bangladesh. [Mimeographed.]

Cook, H L, 1971. Fungi parasitic on shrimp. FAO Aquaculture Bulletin, 3: 13.

Cook, H L & S R Lofton, 1973. Chitinoclastic bacteria associated with shell disease in Penaeus shrimp and blue crab (Callinectes sapidus). Journal of Wildlife Disease, 9: 154–159.

Corliss, J P, 1979. Accumulation and depletion of oxytetracycline in juvenile white shrimp (Penaeus setiferus). Aquaculture, 16 (1): 1–6.

Corliss, J, D V Lightner & Z P Zein-Eldin, 1977. Some effects of oral doses of oxytetracycline on growth, survival and disease in Penaeus setiferus. Aquaculture, 11: 355–362.

Couch, J A, 1976. Attempts to increase Baculovirus prevalence in shrimp by chemical exposure. Progress in Experimental Tumor Research, 20: 304–314.

Couch, J A, 1978. Diseases, parasites and toxic responses of commercial penaeid shrimps of the Gulf of Mexico and South Atlantic coasts of North America. Fishery Bulletin, 76 (1): 1–44.

Couch, J A & L Courtney, 1977. Interaction of chemical pollutants and virus in a crustacean: a novel bioassay system. Annals of the New York Academy of Science, 228: 497–504.

Couch, J A, M D Summers & L Courtney, 1975. Environmental significance of Baculovirus infection in estuarine and marine shrimp. Annals of the New York Academy of Science, 266: 523–536.

Cruz, C L dela, 1983. Fishpond Engineering: A Technical Manual for Smalland Medium-Scale Coastal Fish Farms in SE Asia. South China Sea Programme, SCS Manual no 5, 180 pp.

Donald, D A, J Ure & D V Lightner, 1979. Preliminary results of ozone disinfection of seawater containing the pathogens Vibrio sp and Fusarium solani. Ozone Science Engineering, 1 (4): 329–334.

Dawson, C E, 1958. Observation on the infection of the shrimp, Penaeus semisulcatus by Epipenaeon elegans in the Persian Gulf. Journal of Parasitology, 44: 240–241.

Delves-Broughton, J, 1974. Preliminary investigations into the suitability of a new chemotherapeutic, Furanace, for the treatment of infectious prawn diseases. Aquaculture, 3: 175–185.

Delves-Broughton, J & C W Poupard, 1976. Disease problems of prawns in recirculation systems in the UK. Aquaculture, 7: 201–217.

Egusa, S & T Ueda, 1972. A Fusarium sp associated with black gill disease of the kuruma prawn, Penaeus japonicus Bate. Bulletin of the Japanese Society of Scientific Fisheries, 38: 1253–1260.

El-Gamal, A A, D J Alderman, C J Rodgers, J L Polglase & D MacIntosh, 1986. A scanning electron microscope study of oxolinic acid treatment of burn spot lesions of Macrobrachium rosenbergii. Aquaculture, 52 (3): 157–171.

Euroconsult BV, 1985. Government of Bangladesh and FAO/UNDP. Second Agricultural Research Project - Fisheries Component. FAO/UNDP TA Project BGD/83/010. Technical assistance report no 1 (revised version). Arnhem: Euroconsult BV, 90 pp.

Feigenbaum, D L, 1975. Parasites of the commercial shrimp Penaeus vannamei Bcon and Penaeus brasiliensis Latreille. Bulletin of Marine Sciences. 25: 491–514.

Fisher, W S, E H Nilson & R A Shleser, 1975. Effect of the fungus Haliphthoros milfordensis on the juvenile stages of the American lobster Homarus americanus. Journal of Invertebrate Pathology, 26: 41–45.

Fontaine O T & D V Lightner, 1974. Observations on the phagocytos is and elimination of carmine particles injected into the abdominal musculature of the white shrimp, Penaeus setiferus. Journal of Invertebrate Pathology, 24: 141–148.

Foster, O A, T G Sarphie & W E Hawkins, 1978. Fine structure of the peritrichous ectocommensal Zoothamnium sp with emphasis on its mode of attachment to penaeid shrimp. Journal of Fish Disease, 1 (4): 321–335.

Funegaard, P, 1986. Shrimp seed - Any to sell? Come to Satkhira. Bangladesh. FAO Bay of Bengal News, no 22.

Hatai, K, K Nakajima & S Egusa, 1974. [Effects of various fungicides on the black gill disease of the kuruma prawn (Penaeus japonicus) caused by Fusarium sp.] Fish Pathology, 8: 156–160. [In Japanese.]

Hose, J E & D V Lightner, 1980. Absence of formaldehyde residues in penaeid shrimp exposed to formalin. Aquaculture, 21 (2): 197–201.

Hutton, R F, T Ball & B Eldred, 1962. Immature nematodes of the genus Contracaecum Railliet and Henry 1912, from shrimps. Journal of Parasitology, 48: 327–332.

Ishikawa, Y, 1967. [On the filamentous bacteria which grow on the gills of cultured kuruma prawn.] Fish Pathology, 2: 68–72. [In Japanese.]

Iversen, E S & J F Kelly, 1976. Microspiridiosis successfully transmitted experimentally in pink shrimp. Journal of Invertebrate Pathology, 27: 407– 408.

Johnson, S K, 1974. Ectocommensals and parasites of shrimp from Texas rearing ponds. Sea Grant College, Texas A & M University publication TAMU-SG-74–207, 20 pp.

Johnson, S K, 1974. Ectocommensals and parasites of shrimp from Texas rearing ponds. Proceedings of the World Mariculture Society, 5: 251–266.

Johnson, S K, 1975. Handbook of shrimp diseases. Sea Grant College, Texas, Texas A & M University publication TAMU-SG-75–608, 19 pp.

Johnson, S K, 1977. Crawfish and freshwater shrimp diseases. College Station, Texas, Texas A & M University publication TAMU-SC-77–605.

Johnson, S K, 1982. Diseases of Macrobrachium. In: Giant Prawn Farming, ed M B New, pp 269–277. Amsterdam: Elsevier, 532 pp.

Johnson, S K, J C Parker & H W Holcomb, 1973. Control of Zoothamnium sp on penaeid shrimp. Proceedings of the World Mariculture Society, 5: 321–331.

Karim, M, 1986a. Site selection for the Brackishwater Fisheries Research Station (BFRS). Fisheries Research Institute - Bangladesh, FAO/UNDP TA Project BGD/83/010 report no 11, 44 pp.

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Karim, M, 1986c. Brackishwater shrimp culture demonstration in Bangladesh. SIDA/FAO Bay of Bengal Programme, Madras, India, report BOBP/REP/35, 40 pp.

Karim, M, 1987. Brackishwater aquaculture in Bangladesh: A review. Fisheries Research Institute - Bangladesh, FAO/UNDP TA Project BGD/83/010 report no 12, 36 pp.

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Liao I-C, Yang F-R & Lou S-W, 1977. Preliminary report on some diseases of cultured prawn and their control methods. Tungkang Marine Laboratory, Taiwan Fisheries Research Institute, Pingtung, Taiwan, JCCR Fisheries Series, (29): 28–33.

Lightner, D V, 1975. Some potentially serious disease problems in the culture of penaeid shrimp in North America. Proceedings of the US-Japan Natural Resources Programme Symposium on Aquaculture Diseases, Tokyo, pp 75– 97.

Lightner, D V, 1982. Toxic effect of certain marine blue-green algae to penaeid shrimp. US National Oceanographic and Atmospheric Administration report NOAA-NA-79AA-D-00024, 79 pp. [NTIS order no: PB83-180109.]

Lightner, D V, 1985. A review of the diseases of cultured penaeid shrimps and prawns with emphasis on recent discoveries and developments. Proceedings of the First International Conference on the Culture of Penaeid Shrimps/Prawns, 4–7 December 1984, Iloilo City, Philippines, pp 79–103.

Lightner, D V, L B Colvin, C Brand & D A Donald, 1977. Black death, a disease syndrome of penaeid shrimp related to a dietary deficiency of ascorbic acid. Proceedings of the World Mariculture Society, 8: 611–623.

Lightner, D V & C T Fontaine, 1973. A new fungus disease of the white shrimp Penaeus setiferus. Journal of Invertebrate Pathology, 22: 94–99.

Lightner, D V, C T Fontaine & K Hanks, 1975. Some forms of gill disease in penaeid shrimp. Proceedings of the World Mariculture Society, 6: 347–365.

Lightner, D V, B Hunter, P C Magarelli & L B Colvin, 1979. Ascorbic acid: nutritional requirement and role in wound repair in penaeid shrimp. Proceedings of the World Mariculture Society, 10: 513–528.

Lightner, D V & D H Lewis, 1975. A septicemic bacterial disease syndrome of penaeid shrimp. Marine Fisheries Review, 37: 25–28.

Lightner, D V & R M Redman, 1985. A parvo-like virus disease of penaeid shrimp. Journal of Invertebrate Pathology, 45 (1): 47–53.

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6 Annexe

Solubility of oxygen in Seawater

and

Dissociation of Ammonia in water

Table 5. Solubility of oxygen (mg 1^-1 at 100 % saturation) in water in relation to temperature (0–40 °C) and salinity (0–40 ‰) [moist air: atmospheric pressure 760 mm Hg].

Table 6. Percentage of free ammonia (NH₃) in aqueous* ammonia solutions in relation to temperature (0–30 °C) and pH (6.0–10.0).

* Freshwater.

Notes:

As salinity increases the percentage of free amonnia is reduced slightly. For the purposes of water quality management in aquaculture the difference between fresh and saline water is insignificant.

The percentage ammonia (NH₃) in aqueous solution at different temperatures and pH is based on the following two expressions:

pKa = 0.09018 + (2729.92/t),

where pKa is the ionization constant, and t is the temperature in degrees Kelvin (°K); and

% unionized NH₃ = 1/[10 ^{(pKa - pH)} + 1]