The results of investigatory work undertaken at the five areas suggest that the culture of marine finfishes in floating net cages should have considerable potential for commercial development at least in some parts of Indonesia. Apart from a number of suitable locations identified for this development, the fast tidal water and current transport, the apparently abundant wild fish seed resources, and for some areas the proximity of good market outlets for the end products, are all relevant in this consideration.
To establish the potential and viability of finfish cage culture in Indonesia, a number of five pilot farm sites has been selected for undertaking prescribed programme of culture trials with a view to introducing the technical methodology on the one hand, and eventually to assessing the relative level of performance of cage culture in these areas. The five chosen sites are:
site off Pulai Serai, Siulung island, southern Bintan area, Riau Archipelago (Fig. 1);
site no. 5 in the bay off the township of Batimenyan, Teluk Lampung, Sumatra (Fig. 2);
northern coast of Teluk Gilimanuk, northeast Bali, Bali island (Fig. 3);
Petura Bay, Grajagan, southeast Java (Fig. 4); and
southern bay of Giligenteng, off southeastern tip of Madura island proper, East Java (Fig. 5).
Apart from those noted in Chan (1978 and 1981d), the selection of these pilot farm sites has taken into consideration also a number of convenience factors. In particular:
as far as possible, a site should have direct or indirect access to communication, access road, and power and freshwater supply; and
to facilitate future development, a site should also have ready access to coastal communities to provide the required core labour force for the future commercial development phase.
These five sites are distributed along the length of the country having access to three categories of market outlets: an overseas market having consistently high demand and value for the species to be cultured; the high value market in Jakarta; and the medium to low value market in Surabaya and Sumenep, respectively.
If the growout capacity and the culture management system are the same for all the five sites, much useful information could be revealed for a comparative assessment of the profit margin of cage culture in each of the five areas, as well as for the identification of local constraints and risks affecting such a profit margin.
The design and choice of culture facilities should depend upon the materials locally available, and also their material strength, size and cost. Culture facilities refer to a floating raft so constructed as to provide spaces from which net cages are suspended (Chan 1981c). Indonesia is well endowed with good timber and bamboo, both being excellent materials for the construction of floating rafts. Annex F provides a listing of the principal components and their rough costs for the five sites. These are based on quotes supplied by fisheries personnel responsible for each of the areas concerned.
Each floating raft comprises four 2.5 × 2.5 × 5 m depth net cages. Each pilot farm is assigned two such rafts giving a total number of growout cages of 8 or a total growout biomass holding capacity at harvest of around 2.5 metric tons per crop.
A fish for culture must satisfy a number of basic selection criteria:
its optimal requirements for survival should be met by the environmental conditions at the sites chosen for its culture;
it must be hardy, capable of withstanding handling and other stresses arising from being impounded;
it must have a relatively high average daily weight increment; and
it should fetch a consistently high market value throughout the year.
A number of fishes can meet with these criteria. These include:
Family Serranidae: groupers
Epinephelus tauvina
Epinephelus malabaricus
Epinephelus fuscoguttatus
Plectropomus leopardus
Plectropomus maculatus
Family Lutjanidae: snappers
Lutjanus argentimaculatus
L. johni
L. sanguineus
L. sebae
Family Carangidae: jacks
Caranx spp.
Family Latidae: giant seaperch
Lates calcarifer
Other fishes that fisheries officials at the provinces have expressed desire to include are the rabbitfishes (the Siganidae) and the Waigieu seaperch (Psamoperca waigiensis). These are however, considerably less attractive fish to grow. Table 1 presents a comparative case showing the potential yield per m3 for some of the above-listed species and the gross revenue to be derived therefrom. Any subjectively favoured fishes to be chosen for culture should therefore, be critically reassessed.
There are other independent and dependent variables not yet fully included in the present evaluation chart. For example, cannibalistic behaviour, mortalities (various kinds), ability to withstand stresses, vulnerability to disease infection, feeding satiation point, number of feeding per day, and other pertinent information on the individual species are also equally important in the selection of fishes for culture.
Of the species listed, it is recommended for the pilot culture trial phase to utilise as far as possible Epinephelus tauvina and E. malabaricus either individually or in combination with Plectropomus leopardus and P. maculatus. Although there is a great interest in the culture of Lates calcarifer (the giant seaperch) in the areas visited, it is however, not recommended to be used for the trial phase for the following reasons:
it is a highly cannibalistic serranoid and if not attended properly the stock could suffer over 90% mortality through cannibalism within a matter of a month under cage culture conditions;
it is highly prone to disease infection and handling and other stresses, especially for fry to early fingerling stages kept in sea water conditions;
it requires an intensive feeding programme necessitating not less than three full satiations per day; and
to maintain a healthy, normal fry stock, grading is a continuing process at not less than 5-day intervals, and nutritional requirements in the diet of the fry and early juvenile must be consistently met.
Under the circumstance, the culture of Lates calcarifer should be a problem on its own rather than forming a culture system to be considered within the present seafarming project. It will necessitate altogether very different techniques, management know-how, and in fact the consideration of very different opportunity risks and constraints.
Results of the investigation show that the future development potential of cage culture of marine finfishes in Indonesia could be rather promising. Under good management (Chan 1981b), it is possible to contemplate an optimum biomass carrying capacity of 10 kg per cubic metre of caged water for all of the areas visited.
In extrapolation, basing on an eight-cage culture unit (each cage being 2.5 m × 2.5 m × 5 m deep), it is possible to attain a gross yield of 2.5 metric tons per crop. In this estimation, the size of the fingerling to be stocked was assumed to have a mean weight of 125 gm per fish. From the initial weight the chosen species could attain an average daily weight increment of 4 gm, implying that the time required to produce 605 gm size fish is only 120 days, and 1000 gm fish 219 days. Assuming that stocking materials were available throughout the year, a 605-gm production schedule would theoretically give three crops per year or a theoretical maximum annual gross yield of 7.5 t. On the other hand, a 1000 gm schedule would allow only a maximum annual gross yield of 4 m t. The difference between these two programmes in terms of performance is therefore 3.5 m.t.
In terms of the additional facility, time and feed cost on a per crop basis, however, the total production cost per crop for the latter programme should be in the realm of at least 1.8 times that of the former programme.
In scheduling production programme, it is important to aim at the optimum value size, say, 1000-gm size at the Jakarta market and 605-gm size at the Singaporean market. Because of the theoretical differences in the total annual production costs and in the annual gross yield between the 605-gm and 1000-gm programmes, it would be prudent to realistically attempt the cost and benefit of the two alternative schedules, while noting also the importance of attaining as fast a cash flow as possible.
For the purpose of this somewhat “academic” exercise, pro-forma statements of income each for the Bintan area (Annex C), Teluk Lampung area (Annex D) and the Grajagan area (Annex E) are prepared based on figures provided by the fisheries officials contacted. In these statements, optimum value size is used, and the revenue estimates are based on the wholesale value of the species supplied to the author. Another assumption used in these statements is that the fingerlings for stocking are consistently at a mean weight of 125 gm.
If the degree of accuracy is not the aim, such early extrapolations are useful to forecast the likely performance outcome at each of the proposed pilot farms on the one hand, and to identify the possible distribution of costs for each of the principal inputs on the other.
In this regard, Table 2 summarises the principal dependent and independent variables affecting each of the principal factors in cost and benefit of the future cage culture trial. It also serves to indicate the range of principal problem areas involved in the management of cage culture production operation for development planning consideration.
