2. THE STOCK TRANSFER SYSTEM

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:

• 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

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:

• 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

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:

• 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

Table 3: PNG/Sepik - outline sizing of facilities

Notes:-

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:

• 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;

  • Salmo gairdnerii (rainbow trout);
  • Tilapia rendalli;
  • Cyprinids;

• in the initial stages, ancillary sites would be useful and cost-effective for the following purposes;

  • in stream hatching of rainbow trout;
  • holding and growing broodstock carp, tilapia in ponds or pens

• in later stages, additional locations could also be used for;

  • in stream hatching of Tor, Schizothorax, or other upper river species;
  • enhancing natural spawning of rainbow trout, by providing specific habitat needs;
  • enhancing natural spawning of other upper river species, by similar means;
  • enhancing natural spawning of lower river species.

• in later stages of the project it may also be useful to consider association with government or private centres for;

  • growing broodstock rainbow trout and producing eggs for hatching or distribution;
  • growing broodstock carp, producing and hatching eggs, and growing fry and fingerling;
  • hatching and releasing various species