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:
as near as possible to the main transport routes involved; stage 1 quarantine should be as near as possible to the main import point - in this case Port Moresby airport;
self contained, and isolated from adjacent water bodies or aquatic habitats, using either independent or recycled water systems;
designed to eliminate cross contamination of adjacent stocks, by having separate holding, water and service systems for each stock involved;
capable of being completely cleaned and sterilised between batches, or in the event of a major disease problem;
relatively simple and cheap to set up and operate; versatile and reliable;
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
Once the stock has been appropriately inspected and/or quarantined, steps can be taken for distribution and introduction. There are several possible options:
stocks can be introduced directly as eggs, hatched directly in suitable habitats within the river system, or using simple man-made in-stream hatching devices.;
fry or fingerlings can be introduced, depending on relative suitability, either directly or from eggs hatched in one or more suitably located hatcheries;
broodstock can be reared at suitable locations, from which eggs, fry or fingerling can be distributed as required. There are several factors to be taken into account in choosing between these options:
eggs are usually the simplest to transport, particularly for rough conditions and multiple locations, though helicopter transport may simplify delivery of hatched or part grown stock
facilities for holding and hatching eggs are normally simpler than those for rearing stock, particularly if specialised feeding or environmental requirements are involved.
there is usually a payoff between early lifecycle stage introduction - usually simpler and cheaper - and overall survival of stock, which is better for larger introduced sizes.
the availability of specific habitats, and the relative protection from predation, would have to be assessed for the chosen species and life-cycle stages.
facilities, and hence stocking policies, are likely to be dictated as much by available access, infrastructure, and staffing, as by other factors.
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
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
|Salmo gairdnerii||ponds, tanks, cages enclosures||stripped||troughs, jars gravel boxes||tanks, troughs small cages||tanks, ponds, cages/enclos||seasonal spawning normal; large eggs easy to handle, but need good quality|
|Schizothorax spp.||ponds, enclosures||stripped||troughs, jars gravel boxes||small tanks, troughs||tanks, cages||can use salmonid type systems|
|Tor spp.||ponds, cages enclosures||stripped||jars, troughs||troughs, tanks||ponds, cages tanks||migratory spawner; aquaculture techniques now successful|
|Tilapia rendalli||tanks, ponds, cages enclosures||natural, ponds, tanks, hapas||substrate hapas, jars||hapas, small ponds, tanks||hapas, ponds cages, tanks||large egg batches, substrate spawner|
|Osphronemus goramy||ponds, poss tanks||natural/nests||nests/jars||hapas, small ponds||hapas, ponds||3–4000 eggs in underwater nests; materials have to be provided.|
|Trichogaster pectoralis||ponds||natural/nests||nests||ponds, hapas poss tanks||ponds, poss tanks||bubble nest builders, spawn dry season may be adaptable to artificial methods|
|Cyprinus carpio||ponds, cages enclosures||natural/ponds or stripped||jars, troughs small ponds||ponds, hapas small cages||ponds, cages enclosures||normally seasonal, better production hatched; predation problems in ponds|
|Oreochromis mossambicus||tanks, ponds, cages enclosures||nat'l/ponds, or tanks, hapas||jars, hapas, mouth-brood||hapas, ponds, tanks||tanks, ponds, cages/enclos||non-seasonal, very versatile methods, hatching increases productivity.|
|Prochilodus platensis||ponds, cages||stripped||jars, hapas||hapas, ponds||ponds, cages||migratory spawner, small eggs, can use carp systems|
|Puntius gonionotus||ponds, cages enclosures||ponds, cages hapas||jars, hapas||small ponds, hapas||hapas, cages enclosures||can use carp systems|
|Acrossocheilus spp.||ponds, tanks||stripped/ponds||jars, troughs||ponds, hapas||hapas, cages||experimental results successful|
|Leptobarbus||ponds, cages||natural or stripped||jars, hapas||ponds, hapas troughs||ponds, cages||may use carp systems|
|Labeo rohita||ponds, cages||natural or stripped||jars, troughs hapas||troughs, hapas tanks||ponds, cages tanks||routinely spawned and reared|
|Colossoma spp.||ponds, cages||natural or stripped||jars, troughs||troughs, hapas||ponds, cages||carp-based systems relatively good|
|Mylossoma spp.||ponds, cages||natural or stripped||jars, troughs||troughs, hapas||ponds, cages|
note: ‘hapas’ are small fine-meshed bags suspended inside ponds or enclosures
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:
minimum introduced stock required for the successful establishment of a self-sustaining population,
the rate of buildup of a stock to a useful size, capable of supporting or contributing to a fishery under local conditions
typical batch sizes available, either from single spawning batches or as defined by holding or transport capacity.
relative contribution of the stock to the fishery potential of the river system.
seasonality of stocks involved, and the need for managing specific stock activities at specific times; hence defining capacity suitable for short-term seasonal work, and planning usage to sequence stocks having different seasonal patterns.
means of transfer, etc, its capacity, range, effective coverage relative to survival characteristics of the stock/ lifecycle stage involved, and cost.
time taken for measurable effects to occur - ideally over the medium term, within the scope of the lifetime of the project; this must be set against the scale and cost of the operation.
the overall results of the transfer of stock, and its benefits, compared with the cost of the transfer; the marginal costs of transferring additional lower priority stocks relative to their benefits.
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
|Species||Normal temp range||Spawing/egg characteristics||Spawns per year||Brood stock size, kg||Spawn batch size||Early lifecycle habitat, feeding, survival, etc.||Possible target introduction size and numbers per site|
|Salmo gairdenerii||4–20||migratory seasonal spawner, upper streams||single||0.3–1.0||400–1000||demersal, stream gravel beds, feed on insect larvae, zooplankton, etc|
|Schizothorax spp.||4–20||seasonal migratory, 14–17c upper streams; art. stripping||seasonal||0.1–1.0||4000–50000||stream pools, zooplankton, drift to lower warmer lakes; tanks and art feeds||Part-batch, say 5000 as small fingerlings or batch of eggs for instream hatching|
|Tor spp.||4–20||seasonal, sometimes multiple spawning in streams, or stripped||seasonal||0.1–1.0||1000–10000||demersal eggs, easily predated; fry then to sheltered areas; zooplankton feed||1 to 5 batches of eggs instream or similar number as fry or small fingerling|
|Tilapia rendalli||24–32||non-seasonal, nests, sticky eggs guarded by male||2 to 6||0.1–0.4||2000–3000||shallow pond or lake edges, zooplankton insect larvae feed, predation risks||1 to 10 spawning batches (2 to 20,000); fry 1 to 5 batches (1 to 10,000) of fingerling|
|Osphronemus goramy||25–35||submerged nests built with leaves, detritus etc||multiple||0.5–1.0||3000–4000||shallow ponds, vegetated areas, zooplankt. feeds, chopped leaves, etc||3 to 10 batches of fry or fingerlings|
|Trichogaster pectoralis||25–35||air-bubble nests built by male, floating eggs, spawn dry season||several, seasonal||0.1–0.2||500–1000||fry reared in spawning ponds, feed on zooplankton||5 to 10 batches, fry or fingerlings|
|Cyprinus carpio||15–30||normally seasonal, stripped or naturally spawned||single||0.6–2.0||100–300000||ponds, lakes, zooplankton feeding||Part batch, say 5000 to 10000; small fingerlings|
|Oreochromis mossambicus||20–35||non-seasonal, mouth-brooding by female, can be hatched separately||multiple (3–10)||0.1–0.5||200–300||shallow pond or lake edges, zooplankton insect larvae feed, predation risks||1 to 5 batches of small fingerlings|
|Prochilodus platensis||20–35||seasonal, migrates; art. spawning in ponds, jar incubation of eggs||seasonal||0.3–1.0||250–500000||flooded pools in river systems, feed on zooplankton, insect larvae, etc.||Part of single batch, say 5000 as small fingerlings|
|Puntius gonionotus||20–32||normally seasonal, triggered by temperature changes||seasonal||0.2–0.6||1000–5000||ponds and lakes||1 batch as small fingerlings|
|Acrossocheilus hexagonolepis||15–28||seasonal flood spawner, or held in ponds for stripping||seasonal||0.5–0.8||5000–10000||feed early, will take artificial diets||1 batch as fingerlings|
|Labeo rohita||18–33||normally seasonal, triggered by water level and temperature changes||seasonal||0.3–0.5||50–150000||ponds, floodplains, shallow margins; zooplankton feed||Part-batch, say 10000 as small fingerlings|
|Colossoma macropomus||18–32||riverine spawner||1.0–5.0||200–300000||floodplains, lake areas||Part batch, say 5000 to 10000; small fingerlings|
|Mylossoma duriventris||18–32||riverine spawner||0.3–1.0||na||floodplains, lake areas||Part batch, say 5000 to 10000; small fingerlings|
Table 3: PNG/Sepik - outline sizing of facilities
|Species||Distribution/ stock sites||Typical annual number needed||Brood-stock needed (m+f)||Holding units used||Stock density kg/m3||Brood-stock capacity m3||Fry/fing stock density kg/m3||Ave wt at release; g.||Max.no per cycle||Capacity required m3|
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.
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:
at least one quarantine centre will be required; if necessary this should have facilities for both cold and warm water species. This should have at least stage 1 capability. In the initial phases of the project, with lower-risk species, this may be sufficient for most needs;
additional (stage 2 and/or stage 3) quarantine capacity could be provided at this location, but may be better established in secure locations within the overall environment of the target transfer destinations. If species are selected carefully, this need not be required in the initial stages of the project;
at least two main distribution centres will be required; one for cooler water species, one for warmer water species. These could if necessary be located together with, but separate from, the associated stage 2/3 quarantine facilities. Preferably these should both be located on the Sepik/Ramu catchment unless they are handling species which are already present in any alternative catchment. These should be as simple and versatile as possible, and should make use of existing facilities where possible;
facilities in the quarantine and distribution centres could be sized and specified around the requirements of the following species, to be amended as required for other species;
in the initial stages, ancillary sites would be useful and cost-effective for the following purposes;
in later stages, additional locations could also be used for;
in later stages of the project it may also be useful to consider association with government or private centres for;