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3 Requirements for effective hatchery production


In order to provide practical and effective technical guidance for shrimp hatchery management, it is first necessary to review the basic requirements for an effective hatchery production system. These include the presence of essential infrastructure, the development of Standard Operating Procedures (SOPs) (including Hazard Analysis Critical Control Point (HACCP) analysis), the maintenance of biosecurity, the provision of adequate amounts of clean water, the responsible use of chemicals, and the assurance of health status of stocks through laboratory testing. Many of these components are discussed in more detail in later sections of this document.

3.1 Infrastructure

Hatcheries must be well designed and have adequate infrastructure, as these have an important impact on the quantity and quality of postlarvae produced

Hatcheries should be designed (or modified, in the case of existing hatcheries) to ensure good biosecurity, efficiency, cost-effectiveness and the implementation of the hatchery Standard Operating Procedures (SOPs). The infrastructure requirements for successful biosecurity in the hatchery operation will be discussed under the relevant headings throughout this section.

Shrimp hatcheries should consist of several units, each having appropriate infrastructure

A well-designed shrimp hatchery will consist of separate facilities for quarantine, acclimatization, maturation, spawning and hatching, larval and nursery rearing, indoor and outdoor algal culture, and for the hatching (and enrichment, where applicable) of Artemia. Additionally, there will be supporting infrastructure for the handling of water (facilities for abstraction, storage, filtration, aeration, heating and distribution), and feed (laboratories for analysis and preparation and storage facilities), as well as maintenance areas, packing areas for nauplii and PL, offices, storerooms and staff living quarters.

Good hatchery design should include the physical separation or isolation of the different production facilities and effective perimeter security

The physical separation or isolation of the different production facilities is a feature of good hatchery design and should be incorporated into the construction of new hatcheries. In existing hatcheries with no physical separation, effective isolation may also be achieved through the construction of barriers and implementation of process and product flow controls. The hatchery facility should have a wall or fence around the periphery of the property, with enough height to stop the entrance of animals and unauthorized persons. This will help to reduce the risk of pathogen introduction by this route, as well as increase overall security.

To minimize the possibility of infecting existing broodstock via the introduction of new animals, there should be a quarantine unit for new broodstock

The quarantine of all new animals to be introduced into the hatchery is an essential biosecurity measure. Before passing to the production system, the broodstock must be screened for subclinical levels of pathogens (i.e. via dot blot, polymerase chain reaction (PCR), immunoblot etc.). Broodstock infected with serious untreatable diseases should be destroyed immediately and only animals negative for pathogens introduced to the maturation unit.

3.2 Water quality and treatment

Water treatment systems should be designed to provide high quality oceanic seawater

Water for the hatchery should be filtered and treated to prevent entry of vectors and any pathogens that may be present in the source water. This may be achieved by initial filtering through subsand well points, sand filters (gravity or pressure), or mesh bag filters into the first reservoir or settling tank. Following primary disinfection by chlorination, and after settlement, the water should be filtered again with a finer filter and then disinfected using ultraviolet light (UV) and/or ozone. The use of activated carbon filters, the addition of ethylene diamine tetra acetic acid (EDTA) and temperature and salinity regulation may also be features of the water supply system.

The design of the water distribution system should take into account the level of biosecurity required by the individual areas to which the water is distributed

Each functional unit of the hatchery system should have the appropriate water treatment and, where necessary, should be isolated from the water supply for other areas (for example, quarantine areas). Separate recirculation systems may be used for part or the entire hatchery to reduce water usage and further enhance biosecurity, especially in high-risk areas.

All water discharged from the facility should be free of pathogens

All water discharged from the hatchery, particularly that known or suspected to be contaminated (for example, water originating from the quarantine areas) should be held temporarily and treated with hypochlorite solution (>20 ppm active chlorine for not less than 60 min) or another effective disinfectant prior to discharge. This is particularly crucial where the water is to be discharged to the same location as the abstraction point.

More specific water treatment procedures to be used for each phase of maturation and larval rearing are detailed in the appropriate sections.

3.3 Biosecurity

Good biosecurity must be achieved, as it is paramount to the successful production of healthy PL

Biosecurity has been defined as "...sets of practices that will reduce the probability of a pathogen introduction and its subsequent spread from one place to another..." (Lotz 1997). The basic elements of a biosecurity programme include the physical, chemical and biological methods necessary to protect the hatchery from the consequences of all diseases that represent a high risk. Effective biosecurity requires attention to a range of factors, some disease specific, some not, ranging from purely technical factors to aspects of management and economics. Various levels and strategies for biosecurity may be employed depending on the hatchery facility, the diseases of concern and the level of perceived risk. The appropriate level of biosecurity to be applied will generally be a function of ease of implementation and cost, relative to the impact of the disease on the production operations (Fegan and Clifford 2001). Responsible hatchery operation must also consider the potential risk of disease introduction into the natural environment, and its effects on neighbouring aquaculture operations and the natural fauna.

3.4 Standard operating procedures (SOPs)

Each hatchery should develop its own set of Standard Operating Procedures (SOPs)

Standard Operating Procedures (SOPs) outlining the control protocol for the hatchery should be described in a comprehensive document that covers each stage or process of the production cycle. The document should include details of all of the critical control points (CCP) and describe how to perform each task to control the associated risk. Once the protocol for hatchery operation is documented, the SOPs should be given to all personnel, and a copy should be available for all workers in an accessible place (dining room, meeting room etc.). A meeting should be held to introduce the protocol and explain the need for, and contents of the SOPs. This is a good opportunity to clearly identify and explain any points that generate doubts or that may be misinterpreted and to get practical input from the hatchery staff.

As new information becomes available, it will be necessary to update or modify the SOPs, and any changes must be communicated to all personnel. Any updated version of the SOPs should have the date of the modification and a clear statement that the new version supersedes all previous versions.

All workers should sign a document indicating that they have read and understood the SOPs, and that they will comply with all requirements

All job descriptions of hatchery management and staff should include a clause related to following the SOPs and the disciplinary consequences of failure to comply.

Training in biosecurity maintenance should be an important component of the hatchery process

It is advisable to have a group of people with higher technical training or experience who can supervise and train workers in the execution of each step of the SOPs. This point is of fundamental importance, as the workers may not understand either the standards required or the risks of non-compliance to the success of the hatchery. These technical personnel must organize meetings with the workers for each department to explain and discuss the importance of the execution of the SOPs.

The biosecurity risk posed by each area of the hatchery should be determined

Different areas of the hatchery may be classified according to the level of risk of disease introduction or transfer. Weirich et al. (in press) used this system to describe four classifications:

· Quarantine areas where a pathogen of concern is potentially present or suspected,

· High sensitivity areas requiring minimum exposure to avoid potential pathogen introduction or transfer,

· Medium sensitivity areas with lower risk of pathogen introduction or transfer, and

· Low sensitivity areas in which risks of pathogen introduction or transfer are unlikely.

These classifications can be modified if required and the changes reflected in an updated version of the SOPs. Specific protocols and restrictions may be adopted for each of these biosecurity levels to prevent pathogen entry or transfer.

3.5 Hazard analysis critical control point (HACCP) approach

Development and implementation of biosecurity protocols can be made easier by a Hazard Analysis Critical Control Point (HACCP) approach

The HACCP approach is a preventive risk management system based upon a hazard analysis and has been widely used to identify and control risks to human health in food-processing systems. Critical limits are set at critical control points (CCPs) in the system where controls must be applied to prevent, eliminate or reduce a hazard. Monitoring and corrective actions are then implemented (Weirich et al. in press). HACCP principles have been applied as a risk management tool to control viral pathogens at shrimp research and production facilities (Jahncke et al. 2001).

HACCP analysis should also be applied to shrimp production, with particular emphasis on reducing or preventing disease risks

Maximum biosecurity in shrimp production facilities can be achieved through the isolation of breeding, hatchery and production phases (Jahncke et al. 2001, 2002). Good facility design with a high degree of isolation can help to reduce the risk of transfer of pathogens from broodstock to their offspring. The critical control points (CCP) identified for the maturation and hatchery stages of shrimp production are the shrimp, the feeds and the water. Other potential risks to be covered by the implementation of SOPs and HACCP are disease vectors (human and animal), facilities and equipment.

A flow diagram should be created for the hatchery facility detailing all operations and the movement of shrimp and larvae through the production system

For each operation, from broodstock receipt through maturation, larval rearing and, where applicable, nursery, all potential hazards, impacts on larval health and quality, and points of entry of pathogens should be identified. Following this systematic hazard analysis, CCPs should be identified. For each CCP, critical limits must be established and, where these limits are exceeded, appropriate corrective actions determined. A system to monitor the CCPs must be established along with a good system of documentation and recording.

Critical Control Points (CCPs) must be identified for each area

For different areas such as quarantine, maturation, hatchery, algal culture, Artemia production etc., it is necessary to identify critical control points. The following stages can be considered as CCPs, although these may not be the only ones and they can vary from one location to another:

· Facility entrance: Control at entrance for operational workers, administrative employees, vehicles and other disease vectors to prevent transfer of infections from other hatcheries and the environment at large.

· Water treatment: All the water used in production units must be appropriately (stage dependant) treated (chlorine, ozone, filtration etc.) to kill pathogens and their hosts.

· Maturation: Quarantine of incoming broodstock; checking and disinfection of fresh feed; cleaning of tanks and water and air lines; and disinfection of broodstock, eggs, nauplii and equipment.

· Hatchery: Regular dry-out periods; cleaning and disinfection of buildings, tanks, filters, water and air lines and equipment; quality control and disinfection of fresh feeds; separation of working materials for each room and each tank.

· Algae: Restricted entrance of personnel to algal laboratory and tank facilities; equipment, water and air disinfection; sanitation and quality control of algae and chemicals used.

· Artemia: Cyst disinfection, nauplii disinfection, tank and equipment cleaning and sanitation.

· Restriction of entrance to the hatchery in general and each area in particular to authorized personnel: All staff and administrative personnel entering the production areas must comply with the procedures in the SOPs.

Hatchery workers must be restricted to their specific area of work

The hatchery workers must be restricted to their specific area of work and should not be able to move freely to other areas not assigned to them. One practical way to manage this is to provide different colour uniforms for each area. This will allow quick identification of people in areas where they are not allowed.

The SOPs should address risks due to staff whose duties require them to pass through areas of the hatchery with different biosecurity classifications

For example, communication between staff working in different areas can be maintained while limiting movement between different areas of the hatchery by providing a central area where staff can meet to discuss and plan work schedules, and by communicating by intercom system, radios, text messaging, mobile phones, or a local area network (LAN) for the computer systems.

All staff must take adequate sanitary precautions when entering and leaving a production unit

Rubber boots must be worn by staff when in the production areas. The production units (hatchery, maturation, algal culture, Artemia etc.) must have one entrance/exit to avoid unnecessary through-traffic. The entrance must have a footbath with a solution of calcium (or sodium) hypochlorite with a final concentration not less than 50 ppm active ingredient.

This disinfectant solution must be replaced when necessary. Next to the entrance door, each room must have a bowl with a solution of iodine-PVP (povidone iodine) at 20 ppm and/or 70% alcohol, and personnel must wash their hands in the solution(s) when entering or leaving the room.

Special care must be taken with vehicles (personal or shrimp transport vehicles), because they may have visited other hatcheries or shrimp farms before arrival

All vehicles must pass through a wheel bath with dimensions such as to assure complete washing of the wheels. The wheel bath must be regularly filled with an effective disinfectant solution (such as sodium (calcium) hypochlorite at >100 ppm active ingredient).

The entry of potential disease vectors into the hatchery facility must be controlled

Some shrimp viruses are found in a range of terrestrial animals, such as insects and birds (Lightner 1996, Lightner et al. 1997, Garza et al. 1997). While it is not possible to control all potential animal vectors, their entry can be minimized by the use of physical barriers such as fencing, while nets or mesh can be used to exclude birds and insects.

Aquatic animals can be excluded by ensuring that there are no direct means of entry from open-water sources, especially via inlet pipes and drainage channels. All water entering the facility should filtered and disinfected, and all drainage channels should be screened and/or covered, where possible, to prevent the entry and establishment of wild aquatic animals.

3.6 Chemical use during the hatchery production process

Chemicals must be used responsibly during the hatchery production process

Chemicals (e.g. disinfectants, drugs, antibiotics, hormones etc.) have many uses in the hatchery production process, where they increase production efficiency and reduce the waste of other resources. They are often essential components in such routine activities as tank construction; water quality management; transportation of broodstock, nauplii and PL; feed formulation; manipulation and enhancement of reproduction; growth promotion; disease treatment, and general health management.

However, chemicals must be used in a responsible manner, as they pose a number of potential risks to human health, other aquatic and terrestrial production systems and the natural environment. These include:

· Risks to the environment, such as the potential effects of aquaculture chemicals on water and sediment quality (nutrient enrichment, loading with organic matter etc.), natural aquatic communities (toxicity, disturbance of community structure and resultant impacts on biodiversity), and effects on microorganisms (alteration of microbial communities).

· Risks to human health, such as the dangers to aquaculture workers posed by the handling of feed additives, therapeutants, hormones, disinfectants and vaccines; the risk of developing strains of pathogens that are resistant to antibiotics used in human medicine; and the dangers to consumers posed by ingestion of aquaculture products containing unacceptably high levels of chemical residue.

· Risks to production systems for other domesticated species, such as through the development of drug-resistant bacteria that may cause disease in livestock or poultry.

It is thus essential that only qualified and adequately trained hatchery personnel be permitted to handle chemicals, that the chemical to be used for a particular situation is the most appropriate for the job, and that it is used in the correct manner (e.g. amount, duration and treatment conditions).

Before chemicals are used, management should always consider if other, more environmentally friendly interventions might be equally effective. Effective and safe use and storage of chemicals should be an integral component of the hatchery's Standard Operating Procedures (SOPs). A detailed review of the use of chemicals in shrimp culture, and in other aquaculture systems, can be found in Arthur et al. (2000).

The Office international des épizooties (World Organisation for Animal Health - http://www.oie.int), in its Manual of diagnostics tests and vaccines for aquatic animals provides acceptable and recommended dosages of various chemicals and disinfectants to be used in shrimp aquaculture (http://www.oie.int/eng/normes/fmanual/A_summry.htm) (OIE 2003).

Table 1 provides a summary of chemical names mentioned in this document and how they are used in hatchery production of P. vannamei in Latin America. Some of the dosages (concentrations and exposure times) provided in this table are slightly different from those given in OIE, 2003. The dosages given in Table 1 have been found more effective in P. vannamei hatchery production in Latin America and were agreed by the experts participated in producing this document.

Table 1. Summary of chemicals and there uses mentioned in this document.

Use in Hatchery

Chemical

Recommended Concentration
(Parts Active Ingredient)

Disinfection of inflow seawater

Sodium hypochlorite[2]

20 ppm for not less than 30 min (or 10 ppm for not less than 30 min)

Chelation of heavy metals in inflow seawater

EDTA

Depends on concentrations of heavy metals in water

Disinfection of discharge water

Sodium hypochlorite

>20 ppm for not less than 60 min

Determination of presence of chlorine in water

Ortho-toluidine

3 drops in 5 mL water sample[3]

Neutralization of chlorine in treated water

Sodium thiosulfate

1 ppm for every 1 ppm residual chlorine

Chelation of heavy metals in: broodstock tank water and hatching tank water

EDTA

Must be determined based on heavy metal loading at location up to 20 ppm or both at 20-40 ppm

Disinfection of broodstock upon entry to quarantine

Iodine-PVP

20 ppm

Formalin

50-100 ppm

Disinfection of broodstock following spawning

Iodine-PVP

20 ppm for 15 sec (dip)

Washing and disinfecting eggs

Iodine-PVP or

50-100 ppm for 1-3 min, (or for 10-60 sec)

Formalin, and

100 ppm for 30 sec

Treflan

0.05-0.1 ppm (to reduce fungal infections)

Disposal of discarded larvae

Sodium hypochlorite

20 ppm

Removal of epibiont fouling from postlarvae

Formalin

up to 20-30 ppm for 1 hr with full aeration

Stress testing of postlarvae

Formalin[4]

30 min

Decapsulation of Artemia cysts

Caustic soda (NAOH) and Chlorine liquid[5]

40 g in 4 mL (8-10% active ingredient)

Disinfection of Artemia nauplii

Sodium hypochlorite solution or

20 ppm

Chloramine-T or both

60 ppm for 3 min

Treatment of water in spawning and hatching tanks

Treflan

0.05-0.1 ppm

Footbath

Sodium (calcium) hypochlorite solution

>50 ppm (or >100 ppm)

Disinfection of equipment (containers, hoses, nets, etc.)

Sodium hypochlorite or

20 ppm (or 30 ppm)

Muriatic acid

10% solution

Disinfection of hands

Iodine-PVP or

20 ppm

Alcohol

70%

Cleaning and disinfection of tanks used for broodstock spawning, egg hatching holding for nauplii and postlarvae, hatching of Artemia

Sodium hypochlorite and/or

30 ppm (or 20-30 ppm)

Muriatic acid[6]

10% solution (pH 2-3)

Disinfection of previously cleaned and disinfected tanks prior to starting a new cycle

Muriatic acid

10% solution

Disinfection of algal culture tanks

Sodium hypochlorite followed by

10 ppm

Muriatic acid

10% solution

Disinfection of sand filters

Sodium hypochlorite or

20 ppm

Muriatic acid

10% solution (pH 2-3)

Disinfection of cartridge filters

Sodium hypochlorite or

10 ppm

Muriatic acid

10% solution (pH 2-3) for 1 hr

Washing of feed preparation equipment (knives, tables, mixers, pelletisers, etc.)

Iodine-PVP

20 ppm

3.7 Health assessment

Routine health assessments should be a component of good hatchery management

The health assessment techniques described below for use in shrimp hatcheries are divided into three categories (levels) based on past experience gained from aquatic animal health management activities in Asia. The system was developed to measure the diagnostic capability required to diagnose diseases of aquatic animals, and thus the techniques commonly employed in shrimp hatcheries can be divided into the same three basic categories. The details of the different levels of assessment techniques are given in FAO/NACA (2000, 2001a, 2001b). They provide a simple and convenient separation based on the complexity of the techniques used (Table 2).

Table 2. Diagnostic level descriptions adapted for use in shrimp hatchery systems.

Level 1

Observation of animal and environment. Examination based on gross features.

Level 2

More detailed examination using light microscopy and squash mounts, with and without staining, and basic bacteriology.

Level 3

Use of more complex methods such as molecular techniques and immunodiagnostics (e.g. PCR, dot blots etc.).

Level 1 Health assessment techniques

Level 1 techniques are commonly employed in most hatcheries. Detailed examination of large numbers of larvae is not practical and hatchery operators and technicians frequently use Level 1 techniques to get a preliminary feel for the health status of larvae and to prioritize more detailed examination. Level 1 observations are also frequently sufficient to make a decision about the fate of a hatchery tank or batch of larvae. Selection of nauplii, for example, generally includes a decision based on phototactic response without the need for a more detailed microscopic examination. If a batch of nauplii shows poor phototaxis and weak swimming behaviour, it will be rejected without further examination.

Level 2 Health assessment techniques

Level 2 techniques are also frequently used in the decision-making process in shrimp hatchery management. Most, if not all hatcheries will have a microscope that is used to make more detailed examinations of the condition of the shrimp larvae and to observe directly various health-related features (cleanliness, feeding behaviour, digestion etc.). Many hatcheries also routinely employ basic bacteriology to gain an understanding of the bacterial flora of the tanks and to identify possible pathogens when the larvae become weak or sick. This information may then be used to make a decision on whether the tank should be discarded or treated.

Level 3 Health assessment techniques

Level 3 techniques are becoming more commonly employed in shrimp hatcheries. Polymerase chain reaction (PCR) methods are used for the screening of postlarvae and broodstock for viral diseases, as are dot blot and other immunodiagnostic tests. The various applications of the different diagnostic techniques in a shrimp hatchery are given in Table 3.

Table 3. Use of Level 1, 2 and 3 diagnostics in shrimp hatcheries.

Level 1

Examination of broodstock for general health condition, sex determination, staging of ovarian development, moult staging, removal of sick/moribund individuals.

Selection of nauplii by phototactic response, zoea/mysis stage feeding by observation of faecal strands, larval activity, postlarval activity and behaviour, stress tests.

Level 2

Examination of egg quality by microscope. Checking bacterial flora of normal or moribund animals.

Microscopic examination of naupliar quality. Routine microscopic examination of larval condition and postlarval quality. Checking bacterial flora of rearing water and larvae.

Level 3

Screening of broodstock by dot blot or PCR.

Screening of nauplii and postlarvae by dot blot or PCR.


[2] or calcium hypochlorite
[3] Presence of chlorine is indicated by a yellow colour
[4] Salinity change can also be used.
[5] See page 41 for details
[6] In the past, muriatic acid was referred to 3:1 HCl and HNO3, but currently it is referred to as 34-37% HCl.

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