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2.1 The quarantine system

Regardless of the origin of proposed stocks, some form of initial examination and quarantining will be required. Three levels of quarantine can be identified:

Stage 1 - short term holding, typically 2 to 14 days, suitable for initial inspection prior to clearance to other quarantine stages, or with local transfers, to intermediate holding prior to introduction, etc. At this stage, primary disinfection, gross pathological examination, and sampling for detailed analyses can be done. Secure disposal of unacceptable stocks would also be required. There should be efficient and rapid access to good quality pathological services; bacteriology, parasitology and ideally virology.

Stage 2 - intermediate term holding, typically 2 to 20 weeks, in which primary cleared stock could be held for further observation, additional pathological analyses, and further routine disinfection if required. Disposal facilities are also needed. After this stage, many of the lower risk groups could be made ready for transfer. Reasonable access to pathology services is desirable.

Stage 3 - longer term holding, possibly up to 3 years, for stock which has cleared the other stages, appears to be free of directly discernable disease, but has to be held in reasonably secure conditions until F1 stock can be taken at spawning. Only routine husbandry and disease control facilities should be required, with some access to pathology services.

All quarantine facilities should be:

If possible these should be based at existing centres where staff and infrastructure are already or potentially available. In general, the stringency of operation, etc is greatest at stage 1, and decreases towards stage 3; similarly the level of services, protection, etc is normally greater at stage 1, though capacity is normally smaller.

Details of specific design aspects are given in section 2. Figure 3 shows the typical relationship between quarantine stages.

Figure 3 Outline of proposed quarantine stages

Figure 3

2.2 Distribution and introduction

Once the stock has been appropriately inspected and/or quarantined, steps can be taken for distribution and introduction. There are several possible options:

A typical arrangement would involve one or more main distribution centres, from which stock was received from the quarantine stage, plus several related ancillary centres, from which specialised hatching, fry or fingerling rearing, and/or broodstock production could be carried out. Figure 4 illustrates possible approaches.

Figure 4 Possible approaches to Distribution and Introduction

Figure 4

A number of different systems is available, for which selected examples are summarised in Table 1. For practical purposes, most species are reasonably versatile in their system requirements; many could be supported using relatively simple systems such as cages, ponds, hapas and jar or trough hatching units. However at least two separate distribution systems will be needed; one each for warm and cool water species.

Table 1: Outline species/systems choices

SpeciesPotential systemsNotes
Salmo gairdneriiponds, tanks, cages enclosuresstrippedtroughs, jars gravel boxestanks, troughs small cagestanks, ponds, cages/enclosseasonal spawning normal; large eggs easy to handle, but need good quality
Schizothorax spp.ponds, enclosuresstrippedtroughs, jars gravel boxessmall tanks, troughstanks, cagescan use salmonid type systems
Tor spp.ponds, cages enclosuresstrippedjars, troughstroughs, tanksponds, cages tanksmigratory spawner; aquaculture techniques now successful
Tilapia rendallitanks, ponds, cages enclosuresnatural, ponds, tanks, hapassubstrate hapas, jarshapas, small ponds, tankshapas, ponds cages, tankslarge egg batches, substrate spawner
Osphronemus goramyponds, poss tanksnatural/nestsnests/jarshapas, small pondshapas, ponds3–4000 eggs in underwater nests; materials have to be provided.
Trichogaster pectoralispondsnatural/nestsnestsponds, hapas poss tanksponds, poss tanksbubble nest builders, spawn dry season may be adaptable to artificial methods
Cyprinus carpioponds, cages enclosuresnatural/ponds or strippedjars, troughs small pondsponds, hapas small cagesponds, cages enclosuresnormally seasonal, better production hatched; predation problems in ponds
Oreochromis mossambicustanks, ponds, cages enclosuresnat'l/ponds, or tanks, hapasjars, hapas, mouth-broodhapas, ponds, tankstanks, ponds, cages/enclosnon-seasonal, very versatile methods, hatching increases productivity.
Prochilodus platensisponds, cagesstrippedjars, hapashapas, pondsponds, cagesmigratory spawner, small eggs, can use carp systems
Puntius gonionotusponds, cages enclosuresponds, cages hapasjars, hapassmall ponds, hapashapas, cages enclosurescan use carp systems
Acrossocheilus spp.ponds, tanksstripped/pondsjars, troughsponds, hapashapas, cagesexperimental results successful
Leptobarbusponds, cagesnatural or strippedjars, hapasponds, hapas troughsponds, cagesmay use carp systems
Labeo rohitaponds, cagesnatural or strippedjars, troughs hapastroughs, hapas tanksponds, cages tanksroutinely spawned and reared
Colossoma spp.ponds, cagesnatural or strippedjars, troughstroughs, hapasponds, cagescarp-based systems relatively good
Mylossoma spp.ponds, cagesnatural or strippedjars, troughstroughs, hapasponds, cages 

note: ‘hapas’ are small fine-meshed bags suspended inside ponds or enclosures

2.3 Sizing and specifying the transfer system

While Table 1 indicates the overall possibilities or options for the different species involved, it is also important to consider the relevant numerical aspects, such as:

Tables 2 and 3 summarise some of the main characteristics of the transfer operation, and provide initial indications of the size and relative costs of facilities. Specific details are given in the next sections.

Table 2: PNG/Sepik - basic species characteristics

SpeciesNormal temp rangeSpawing/egg characteristicsSpawns per yearBrood stock size, kgSpawn batch sizeEarly lifecycle habitat, feeding, survival, etc.Possible target introduction size and numbers per site
Salmo gairdenerii4–20migratory seasonal spawner, upper streamssingle0.3–1.0400–1000demersal, stream gravel beds, feed on insect larvae, zooplankton, etc 
Schizothorax spp.4–20seasonal migratory, 14–17c upper streams; art. strippingseasonal0.1–1.04000–50000stream pools, zooplankton, drift to lower warmer lakes; tanks and art feedsPart-batch, say 5000 as small fingerlings or batch of eggs for instream hatching
Tor spp.4–20seasonal, sometimes multiple spawning in streams, or strippedseasonal0.1–1.01000–10000demersal eggs, easily predated; fry then to sheltered areas; zooplankton feed1 to 5 batches of eggs instream or similar number as fry or small fingerling
Tilapia rendalli24–32non-seasonal, nests, sticky eggs guarded by male2 to 60.1–0.42000–3000shallow pond or lake edges, zooplankton insect larvae feed, predation risks1 to 10 spawning batches (2 to 20,000); fry 1 to 5 batches (1 to 10,000) of fingerling
Osphronemus goramy25–35submerged nests built with leaves, detritus etcmultiple0.5–1.03000–4000shallow ponds, vegetated areas, zooplankt. feeds, chopped leaves, etc3 to 10 batches of fry or fingerlings
Trichogaster pectoralis25–35air-bubble nests built by male, floating eggs, spawn dry seasonseveral, seasonal0.1–0.2500–1000fry reared in spawning ponds, feed on zooplankton5 to 10 batches, fry or fingerlings
Cyprinus carpio15–30normally seasonal, stripped or naturally spawnedsingle0.6–2.0100–300000ponds, lakes, zooplankton feedingPart batch, say 5000 to 10000; small fingerlings
Oreochromis mossambicus20–35non-seasonal, mouth-brooding by female, can be hatched separatelymultiple (3–10)0.1–0.5200–300shallow pond or lake edges, zooplankton insect larvae feed, predation risks1 to 5 batches of small fingerlings
Prochilodus platensis20–35seasonal, migrates; art. spawning in ponds, jar incubation of eggsseasonal0.3–1.0250–500000flooded pools in river systems, feed on zooplankton, insect larvae, etc.Part of single batch, say 5000 as small fingerlings
Puntius gonionotus20–32normally seasonal, triggered by temperature changesseasonal0.2–0.61000–5000ponds and lakes1 batch as small fingerlings
Acrossocheilus hexagonolepis15–28seasonal flood spawner, or held in ponds for strippingseasonal0.5–0.85000–10000feed early, will take artificial diets1 batch as fingerlings
Labeo rohita18–33normally seasonal, triggered by water level and temperature changesseasonal0.3–0.550–150000ponds, floodplains, shallow margins; zooplankton feedPart-batch, say 10000 as small fingerlings
Colossoma macropomus18–32riverine spawner 1.0–5.0200–300000floodplains, lake areasPart batch, say 5000 to 10000; small fingerlings
Mylossoma duriventris18–32riverine spawner 0.3–1.0nafloodplains, lake areasPart batch, say 5000 to 10000; small fingerlings

Table 3: PNG/Sepik - outline sizing of facilities

SpeciesDistribution/ stock sitesTypical annual number neededBrood-stock needed (m+f)Holding units usedStock density kg/m3Brood-stock capacity m3Fry/fing stock density kg/m3Ave wt at release; per cycleCapacity required m3
Schizothorax spp2010000040tank/cage5651070000140
Tor spp2010000060pond/cage225031040000130
Salmo gairdnerii2020000150tank/cage5205151200036
Puntius gonionotus104000040pond120031030000100
Labeo rohita101000006pond/tank1331080000260
Cyprinus carpio101000006pond/tank1105104000080
Oreochromis mossambicus1020000100tank/cage810510800016
Tilapia rendalli1010000060tank/cage56552000020
Osphronemus goramy612000080pond/cage170354000066
Trichogaster pectoralis42000080pond11203101000033
Prochilodus spp10500006pond/cage2351050000100
Colossoma spp6600006pond/tank12031540000200
Mylossoma spp66000010pond/tank12031040000160


1) The numbers suggested are for demonstration, but correspond typically with the small relaease number/ small number of sites approach typical of initial introductions. If greater numbers or larger sized individuals are required, rearing facilities would be correspondingly enlarged. In practice, one set of facilities should be capable of handling several species in sequential crop cycles, in which case only broodstock capacity need be provided for the separate species, while fry or fingerling production can share common facilities.

2) A simple assessment of the effects of these introductions may be made by considering the time and possible survival to maturation, the overall fecundity, the likely spawning success in the introduced environment, and the potential survival of recruits.

2.4 Preliminary conclusions

While it is difficult at this stage to specify the particular performance characteristics of stocks and their holding and transfer systems, the following preliminary conclusions can be made:

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